Lubiprostone

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# Overview
Lubiprostone is a chloride channel activator that is FDA approved for the {{{indicationType}}} of chronic idiopathic constipation in adults, opioid-induced constipation in adults with chronic, non-cancer pain, irritable bowel syndrome with constipation in women  18 years old.   Common adverse reactions include nausea, diarrhea, headache, abdominal pain, abdominal distension, and flatulence.

# Adult Indications and Dosage

## FDA-Labeled Indications and Dosage (Adult)
- Dosing Information
- The recommended dose is 24 mcg twice daily orally with food and water.
- Dosage in patients with hepatic impairment
- For patients with moderately impaired hepatic function (Child-Pugh Class B), the recommended starting dose is 16 mcg twice daily. For patients with severely impaired hepatic function (Child-Pugh Class C), the recommended starting dose is 8 mcg twice daily. If this dose is tolerated and an adequate response has not been obtained after an appropriate interval, doses can then be escalated to full dosing with appropriate monitoring of patient response.
- Dosing Information
- The recommended dose is 8 mcg twice daily orally with food and water.
- Dosage in patients with hepatic impairment
- For patients with severely impaired hepatic function (Child-Pugh Class C), the recommended starting dose is 8 mcg once daily. If this dose is tolerated and an adequate response has not been obtained after an appropriate interval, doses can then be escalated to full dosing with appropriate monitoring of patient response. Dosage adjustment is not required for patients with moderately impaired hepatic function (Child-Pugh Class B).
- Amitiza is indicated for the treatment of opioid-induced constipation (OIC) in adults with chronic non-cancer pain.
- Limitations of Use:
- Effectiveness of Amitiza in the treatment of opioid-induced constipation in patients taking diphenylheptaneopioids (e.g., methadone) has not been established.

## Off-Label Use and Dosage (Adult)

### Guideline-Supported Use
There is limited information regarding Off-Label Guideline-Supported Use of Lubiprostone in adult patients.

### NonGuideline-Supported Use
There is limited information regarding Off-Label NonGuideline-Supported Use of Lubiprostone in adult patients.

# Pediatric Indications and Dosage

## FDA-Labeled Indications and Dosage (Pediatric)
There is limited information regarding FDA-Labeled Use of Lubiprostone in pediatric patients.

## Off-Label Use and Dosage (Pediatric)

### Guideline-Supported Use
There is limited information regarding Off-Label Guideline-Supported Use of Lubiprostone in pediatric patients.

### NonGuideline-Supported Use
There is limited information regarding Off-Label NonGuideline-Supported Use of Lubiprostone in pediatric patients.

# Contraindications
- Amitiza is contraindicated in patients with known or suspected mechanical gastrointestinal obstruction.

# Warnings

### Precautions
- Nausea
- Patients taking Amitiza may experience nausea. Concomitant administration of food with Amitiza may reduce symptoms of nausea.
- Diarrhea
- Amitiza should not be prescribed to patients that have severe diarrhea. Patients should be aware of the possible occurrence of diarrhea during treatment. Patients should be instructed to discontinue Amitiza and inform their physician if severe diarrhea occurs.
- Dyspnea
- In clinical trials, dyspnea was reported by 3%, 1%, and < 1% of the treated CIC, OIC, and IBS-C populations receiving Amitiza, respectively, compared to 0%, 1%, and < 1% of placebo-treated patients. There have been postmarketing reports of dyspnea when using Amitiza 24 mcg twice daily. Some patients have discontinued treatment because of dyspnea. These events have usually been described as a sensation of chest tightness and difficulty taking in a breath, and generally have an acute onset within 3060 minutes after taking the first dose. They generally resolve within a few hours after taking the dose, but recurrence has been frequently reported with subsequent doses.
- Bowel Obstruction
- In patients with symptoms suggestive of mechanical gastrointestinal obstruction, perform a thorough evaluation to confirm the absence of an obstruction prior to initiating therapy with Amitiza.

# Adverse Reactions

## Clinical Trials Experience
- Because clinical studies are conducted under widely varying conditions, adverse reaction rates observed in the clinical studies of a drug cannot be directly compared to rates in the clinical studies of another drug and may not reflect the rates observed in practice.
- During clinical development of Amitiza for CIC, OIC, and IBS-C, 1234 patients were treated with Amitiza for 6 months and 524 patients were treated for 1 year (not mutually exclusive).
- Chronic Idiopathic Constipation
- Adverse reactions in dose-finding, efficacy, and long-term clinical studies: The data described below reflect exposure to Amitiza 24 mcg twice daily in 1113 patients with chronic idiopathic constipation over 3- or 4-week, 6-month, and 12-month treatment periods; and from 316 patients receiving placebo over short-term exposure ( 4 weeks). The placebo population (N = 316) had a mean age of 47.8 (range 2181) years; was 87.3% female; 80.7% Caucasian, 10.1% African American, 7.3% Hispanic, 0.9% Asian; and 11.7% elderly ( 65 years of age). Of those patients treated with Amitiza 24 mcg twice daily (N=1113), the mean age was 50.3 (range 19-86) years; 86.9% were female; 86.1% Caucasian, 7.6% African American, 4.7% Hispanic, 1.0% Asian; and 16.7% elderly ( 65 years of age). Table 1 presents data for the adverse reactions that occurred in at least 1% of patients who received Amitiza 24 mcg twice daily and that occurred more frequently with study drug than placebo.
- The most common adverse reactions (incidence > 4%) in CIC were nausea, diarrhea, headache, abdominal pain, abdominal distension, and flatulence.
- Nausea: Approximately 29% of patients who received Amitiza 24 mcg twice daily experienced nausea; 4% of patients had severe nausea and 9% of patients discontinued treatment due to nausea. The rate of nausea associated with Amitiza 24 mcg twice daily was lower among male (8%) and elderly (19%) patients. No patients in the clinical studies were hospitalized due to nausea.
- Diarrhea: Approximately 12% of patients who received Amitiza 24 mcg twice daily experienced diarrhea; 2% of patients had severe diarrhea and 2% of patients discontinued treatment due to diarrhea.
- Electrolytes: No serious adverse reactions of electrolyte imbalance were reported in clinical studies, and no clinically significant changes were seen in serum electrolyte levels in patients receiving Amitiza.
- Less common adverse reactions: The following adverse reactions (assessed by investigator as probably or definitely related to treatment) occurred in less than 1% of patients receiving Amitiza 24 mcg twice daily in clinical studies, occurred in at least two patients, and occurred more frequently in patients receiving study drug than those receiving placebo: fecal incontinence, muscle cramp, defecation urgency, frequent bowel movements, hyperhidrosis, pharyngolaryngeal pain, intestinal functional disorder, anxiety, cold sweat, constipation, cough, dysgeusia, eructation, influenza, joint swelling, myalgia, pain, syncope, tremor, decreased appetite.
- Opioid-induced Constipation
- Adverse reactions in efficacy and long-term clinical studies: The data described below reflect exposure to Amitiza 24 mcg twice daily in 860 patients with OIC for up to 12 months and from 632 patients receiving placebo twice daily for up to 12 weeks. The total population (N = 1492) had a mean age of 50.4 (range 2089) years; was 62.7% female; 82.7% Caucasian, 14.2% African American, 0.8% American Indian/Alaska Native, 0.8% Asian; 5.2% were of Hispanic ethnicity; and 8.8% were elderly ( 65 years of age). Table 2 presents data for the adverse reactions that occurred in at least 1% of patients who received Amitiza 24 mcg twice daily and that occurred more frequently with study drug than placebo.
- The most common adverse reactions (incidence > 4%) in OIC were nausea and diarrhea.
- Nausea: Approximately 11% of patients who received Amitiza 24 mcg twice daily experienced nausea; 1% of patients had severe nausea and 2% of patients discontinued treatment due to nausea.
- Diarrhea: Approximately 8% of patients who received Amitiza 24 mcg twice daily experienced diarrhea; 2% of patients had severe diarrhea and 1% of patients discontinued treatment due to diarrhea.
- Less common adverse reactions: The following adverse reactions (assessed by investigator as probably or definitely related to treatment) occurred in less than 1% of patients receiving Amitiza 24 mcg twice daily in clinical studies, occurred in at least two patients, and occurred more frequently in patients receiving study drug than those receiving placebo: fecal incontinence, blood potassium decreased.
- Irritable Bowel Syndrome with Constipation
- Adverse reactions in dose-finding, efficacy, and long-term clinical studies: The data described below reflect exposure to Amitiza 8 mcg twice daily in 1011 patients with IBS-C for up to 12 months and from 435 patients receiving placebo twice daily for up to 16 weeks. The total population (N = 1267) had a mean age of 46.5 (range 1885) years; was 91.6% female; 77.5% Caucasian, 12.9% African American, 8.6% Hispanic, 0.4% Asian; and 8.0% elderly ( 65 years of age). Table 3 presents data for the adverse reactions that occurred in at least 1% of patients who received Amitiza 8 mcg twice daily and that occurred more frequently with study drug than placebo.
- The most common adverse reactions (incidence > 4%) in IBS-C were nausea, diarrhea, and abdominal pain.
- Nausea: Approximately 8% of patients who received Amitiza 8 mcg twice daily experienced nausea; 1% of patients had severe nausea and 1% of patients discontinued treatment due to nausea.
- Diarrhea: Approximately 7% of patients who received Amitiza 8 mcg twice daily experienced diarrhea; <1% of patients had severe diarrhea and <1% of patients discontinued treatment due to diarrhea.
- Less common adverse reactions: The following adverse reactions (assessed by investigator as probably related to treatment) occurred in less than 1% of patients receiving Amitiza 8 mcg twice daily in clinical studies, occurred in at least two patients, and occurred more frequently in patients receiving study drug than those receiving placebo: dyspepsia, loose stools, vomiting, fatigue, dry mouth, edema, increased alanine aminotransferase, increased aspartate aminotransferase, constipation, eructation, gastroesophageal reflux disease, dyspnea, erythema, gastritis, increased weight, palpitations, urinary tract infection, anorexia, anxiety, depression, fecal incontinence, fibromyalgia, hard feces, lethargy, rectal hemorrhage, pollakiuria.

## Postmarketing Experience
- The following additional adverse reactions have been identified during post-approval use of Amitiza. Because these reactions are reported voluntarily from a population of uncertain size, it is not always possible to reliably estimate their frequency or establish a causal relationship to drug exposure.
- Voluntary reports of adverse reactions occurring with the use of Amitiza include the following: syncope, ischemic colitis, hypersensitivity/allergic-type reactions (including rash, swelling, and throat tightness), malaise, tachycardia, muscle cramps or muscle spasms, and asthenia.

# Drug Interactions
- No in vivo drug-drug interaction studies have been performed with Amitiza.
- Based upon the results of in vitro human microsome studies, there is low likelihood of pharmacokinetic drug-drug interactions. In vitro studies using human liver microsomes indicate that cytochrome P450 isoenzymes are not involved in the metabolism of lubiprostone. Further in vitro studies indicate microsomal carbonyl reductase may be involved in the extensive biotransformation of lubiprostone to the metabolite M3. Additionally, in vitro studies in human liver microsomes demonstrate that lubiprostone does not inhibit cytochrome P450 isoforms 3A4, 2D6, 1A2, 2A6, 2B6, 2C9, 2C19, or 2E1, and in vitro studies of primary cultures of human hepatocytes show no induction of cytochrome P450 isoforms 1A2, 2B6, 2C9, and 3A4 by lubiprostone. Based on the available information, no protein bindingmediated drug interactions of clinical significance are anticipated.
- Interaction potential with diphenylheptane opioids (e.g. methadone): Non-clinical studies have shown opioids of the diphenylheptane chemical class (e.g., methadone) to dose-dependently reduce the activation of ClC-2 by lubiprostone in the gastrointestinal tract. There is a possibility of a dose-dependent decrease in the efficacy of Amitiza in patients using diphenylheptane opioids.

# Use in Specific Populations

### Pregnancy
Pregnancy Category (FDA):
- Pregnancy Category C
- Risk Summary
- There are no adequate and well-controlled studies with Amitiza in pregnant women. A dose dependent increase in fetal loss was observed in pregnant guinea pigs that received lubiprostone doses equivalent to 0.2 to 6 times the maximum recommended human dose (MRHD) based on body surface area (mg/m2). Animal studies did not show an increase in structural malformations. Amitiza should be used during pregnancy only if the potential benefit justifies the potential risk to the fetus.
- Clinical Considerations
- Current available data suggest that miscarriage occurs in 15-18% of clinically recognized pregnancies, regardless of any drug exposure. Consider the risks and benefits of available therapies when treating a pregnant woman for chronic idiopathic constipation, opioid-induced constipation or irritable bowel syndrome with constipation.
- Animal Data
- In developmental toxicity studies, pregnant rats and rabbits received oral lubiprostone during organogenesis at doses up to approximately 338 times (rats) and approximately 34 times (rabbits) the maximum recommended human dose (MHRD) based on body surface area (mg/m2). Maximal animal doses were 2000 mcg/kg/day (rats) and 100 mcg/kg/day (rabbits). In rats, there were increased incidences of early resorptions and soft tissue malformations (situs inversus, cleft palate) at the 2000 mcg/kg/day dose; however, these effects were probably secondary to maternal toxicity. A dose-dependent increase in fetal loss occurred when guinea pigs received lubiprostone after the period of organogenesis, on days 40 to 53 of gestation, at daily oral doses of 1, 10, and 25 mcg/kg/day (approximately 0.2, 2 and 6 times the MRHD based on body surface area (mg/m2)). The potential of lubiprostone to cause fetal loss was also examined in pregnant Rhesus monkeys. Monkeys received lubiprostone post-organogenesis on gestation days 110 through 130 at daily oral doses of 10 and 30 mcg/kg/day (approximately 3 and 10 times the MHRD based on body surface area (mg/m2)). Fetal loss was noted in one monkey from the 10-mcg/kg dose group, which is within normal historical rates for this species. There was no drug-related adverse effect seen in monkeys.
Pregnancy Category (AUS):
- Australian Drug Evaluation Committee (ADEC) Pregnancy Category
There is no Australian Drug Evaluation Committee (ADEC) guidance on usage of Lubiprostone in women who are pregnant.

### Labor and Delivery
There is no FDA guidance on use of Lubiprostone during labor and delivery.

### Nursing Mothers
- It is not known whether lubiprostone is excreted in human milk. In rats, neither lubiprostone nor its active metabolites were detectable in breast milk following oral administration of lubiprostone. Because lubiprostone increases fluid secretion in the intestine and intestinal motility, human milk-fed infants should be monitored for diarrhea. Caution should be exercised when Amitiza is administered to a nursing woman.

### Pediatric Use
There is no FDA guidance on the use of Lubiprostone with respect to pediatric patients.

### Geriatic Use
- Chronic Idiopathic Constipation
- The efficacy of Amitiza in the elderly ( 65 years of age) subpopulation was consistent with the efficacy in the overall study population. Of the total number of constipated patients treated in the dose-finding, efficacy, and long-term studies of Amitiza, 15.5% were  65 years of age, and 4.2% were  75 years of age. Elderly patients taking Amitiza 24 mcg twice daily experienced a lower rate of associated nausea compared to the overall study population taking Amitiza (19% vs. 29%, respectively).
- Opioid-induced Constipation
- The safety profile of Amitiza in the elderly ( 65 years of age) subpopulation (8.8% were  65 years of age and 1.6% were  75 years of age) was consistent with the safety profile in the overall study population. Clinical studies of Amitiza did not include sufficient numbers of patients aged 65 years and over to determine whether they respond differently from younger patients.
- Irritable Bowel Syndrome with Constipation
- The safety profile of Amitiza in the elderly ( 65 years of age) subpopulation (8.0% were  65 years of age and 1.8% were  75 years of age) was consistent with the safety profile in the overall study population. Clinical studies of Amitiza did not include sufficient numbers of patients aged 65 years and over to determine whether they respond differently from younger patients.

### Gender
There is no FDA guidance on the use of Lubiprostone with respect to specific gender populations.

### Race
There is no FDA guidance on the use of Lubiprostone with respect to specific racial populations.

### Renal Impairment
- No dosage adjustment is required in patients with renal impairment.

### Hepatic Impairment
- Patients with moderate hepatic impairment (Child-Pugh Class B) and severe hepatic impairment (Child-Pugh Class C) experienced markedly higher systemic exposure of lubiprostone active metabolite M3, when compared to normal subjects. Clinical safety results demonstrated an increased incidence and severity of adverse events in subjects with greater severity of hepatic impairment.
- In case of chronic idiopathic constipation or opioid-induced constipation indications, the starting dosage of Amitiza should be reduced in patients with moderate hepatic impairment. The starting dose of Amitiza should be reduced in all patients with severe hepatic impairment, regardless of the indication. No dosing adjustment is required in patients with mild hepatic impairment (Child-Pugh Class A).

### Females of Reproductive Potential and Males
There is no FDA guidance on the use of Lubiprostone in women of reproductive potentials and males.

### Immunocompromised Patients
There is no FDA guidance one the use of Lubiprostone in patients who are immunocompromised.

# Administration and Monitoring

### Administration
- Oral

### Monitoring
There is limited information regarding Monitoring of Lubiprostone in the drug label.

# IV Compatibility
There is limited information regarding IV Compatibility of Lubiprostone in the drug label.

# Overdosage

## Acute Overdose

### Signs and Symptoms
- There have been two confirmed reports of overdosage with Amitiza. The first report involved a 3-year-old child who accidentally ingested 7 or 8 capsules of 24 mcg of Amitiza and fully recovered. The second report was a study patient who self-administered a total of 96 mcg of Amitiza per day for 8 days. The patient experienced no adverse reactions during this time. Additionally, in a Phase 1 cardiac repolarization study, 38 of 51 healthy volunteers given a single oral dose of 144 mcg of Amitiza (6 times the highest recommended dose) experienced an adverse event that was at least possibly related to the study drug. Adverse reactions that occurred in at least 1% of these volunteers included the following: nausea (45%), diarrhea (35%), vomiting (27%), dizziness (14%), headache (12%), abdominal pain (8%), flushing/hot flash (8%), retching (8%), dyspnea (4%), pallor (4%), stomach discomfort (4%), anorexia (2%), asthenia (2%), chest discomfort (2%), dry mouth (2%), hyperhidrosis (2%), and syncope (2%).

## Chronic Overdose
There is limited information regarding Chronic Overdose of Lubiprostone in the drug label.

# Pharmacology

## Mechanism of Action
- Lubiprostone is a locally acting chloride channel activator that enhances a chloride-rich intestinal fluid secretion without altering sodium and potassium concentrations in the serum. Lubiprostone acts by specifically activating ClC-2, which is a normal constituent of the apical membrane of the human intestine, in a protein kinase Aindependent fashion.
- By increasing intestinal fluid secretion, lubiprostone increases motility in the intestine, thereby facilitating the passage of stool and alleviating symptoms associated with chronic idiopathic constipation. Patch clamp cell studies in human cell lines have indicated that the majority of the beneficial biological activity of lubiprostone and its metabolites is observed only on the apical (luminal) portion of the gastrointestinal epithelium.
- Lubiprostone, via activation of apical ClC-2 channels in intestinal epithelial cells, bypasses the antisecretory action of opiates that results from suppression of secretomotor neuron excitability.
- Activation of ClC-2 by lubiprostone has also been shown to stimulate recovery of mucosal barrier function and reduce intestinal permeability via the restoration of tight junction protein complexes in ex vivo studies of ischemic porcine intestine.

## Structure
- Amitiza (lubiprostone) is a chloride channel activator for oral use.
- The chemical name for lubiprostone is ()-7-pyran-5-yl]heptanoic acid. The molecular formula of lubiprostone is C20H32F2O5 with a molecular weight of 390.46 and a chemical structure as follows:
- Lubiprostone drug substance occurs as white, odorless crystals or crystalline powder, is very soluble in ether and ethanol, and is practically insoluble in hexane and water. Amitiza is available as an imprinted, oval, soft gelatin capsule in two strengths. Pink capsules contain 8 mcg of lubiprostone and the following inactive ingredients: medium-chain triglycerides, gelatin, sorbitol, ferric oxide, titanium dioxide, and purified water. Orange capsules contain 24 mcg of lubiprostone and the following inactive ingredients: medium-chain triglycerides, gelatin, sorbitol, FD&C Red #40, D&C Yellow #10, and purified water.

## Pharmacodynamics
- Although the pharmacologic effects of lubiprostone in humans have not been fully evaluated, animal studies have shown that oral administration of lubiprostone increases chloride ion transport into the intestinal lumen, enhances fluid secretion into the bowels, and improves fecal transit.

## Pharmacokinetics
- Lubiprostone has low systemic availability following oral administration and concentrations of lubiprostone in plasma are below the level of quantitation (10 pg/mL). Therefore, standard pharmacokinetic parameters such as area under the curve (AUC), maximum concentration (Cmax), and half-life (t12) cannot be reliably calculated. However, the pharmacokinetic parameters of M3 (only measurable active metabolite of lubiprostone) have been characterized. Gender has no effect on the pharmacokinetics of M3 following the oral administration of lubiprostone.
- Absorption
- Concentrations of lubiprostone in plasma are below the level of quantitation (10 pg/mL) because lubiprostone has a low systemic availability following oral administration. Peak plasma levels of M3, after a single oral dose with 24 mcg of lubiprostone, occurred at approximately 1.10 hours. The Cmax was 41.5 pg/mL and the mean AUC0t was 57.1 pghr/mL. The AUC0t of M3 increases dose proportionally after single 24-mcg and 144-mcg doses of lubiprostone.
- Distribution
- In vitro protein binding studies indicate lubiprostone is approximately 94% bound to human plasma proteins. Studies in rats given radiolabeled lubiprostone indicate minimal distribution beyond the gastrointestinal tissues. Concentrations of radiolabeled lubiprostone at 48 hours post-administration were minimal in all tissues of the rats.
- Metabolism
- The results of both human and animal studies indicate that lubiprostone is rapidly and extensively metabolized by 15-position reduction, -chain -oxidation, and -chain -oxidation. These biotransformations are not mediated by the hepatic cytochrome P450 system but rather appear to be mediated by the ubiquitously expressed carbonyl reductase. M3, a metabolite of lubiprostone found in both humans and animals, is formed by the reduction of the carbonyl group at the 15-hydroxy moiety that consists of both -hydroxy and -hydroxy epimers. M3 makes up less than 10% of the dose of radiolabeled lubiprostone. Animal studies have shown that metabolism of lubiprostone rapidly occurs within the stomach and jejunum, most likely in the absence of any systemic absorption.
- Elimination
- Lubiprostone could not be detected in plasma; however, M3 has a t12 ranging from 0.9 to 1.4 hours. After a single oral dose of 72 mcg of 3H-labeled lubiprostone, 60% of total administered radioactivity was recovered in the urine within 24 hours and 30% of total administered radioactivity was recovered in the feces by 168 hours. Lubiprostone and M3 are only detected in trace amounts in human feces.
- Food Effect
- A study was conducted with a single 72-mcg dose of 3H-labeled lubiprostone to evaluate the potential of a food effect on lubiprostone absorption, metabolism, and excretion. Pharmacokinetic parameters of total radioactivity demonstrated that Cmax decreased by 55% while AUC0 was unchanged when lubiprostone was administered with a high-fat meal. The clinical relevance of the effect of food on the pharmacokinetics of lubiprostone is not clear. However, lubiprostone was administered with food and water in a majority of clinical trials.
- Special Populations
- Renal Impairment
- Sixteen subjects, 3447 years old (8 severe renally impaired subjects ] (CrCl)  80 mL/min]), received a single oral 24-mcg dose of Amitiza. Following administration, lubiprostone plasma concentrations were below the limit of quantitation (10 pg/mL). Plasma concentrations of M3 were within the range of exposure from previous clinical experience with Amitiza.
- Hepatic Impairment
- Twenty-five subjects, 3878 years old (9 with severe hepatic impairment , 8 with moderate impairment , and 8 with normal liver function), received either 12 mcg or 24 mcg of Amitiza under fasting conditions. Following administration, lubiprostone plasma concentrations were below the limit of quantitation (10 pg/mL) except for two subjects. In moderately and severely impaired subjects, the Cmax and AUC0t of the active lubiprostone metabolite M3 were increased, as shown in Table 4.
- These results demonstrate that there is a correlation between increased exposure of M3 and severity of hepatic impairment.

## Nonclinical Toxicology
- Carcinogenesis
- Two 2-year oral (gavage) carcinogenicity studies (one in Crl:B6C3F1 mice and one in Sprague-Dawley rats) were conducted with lubiprostone. In the 2-year carcinogenicity study in mice, lubiprostone doses of 25, 75, 200, and 500 mcg/kg/day (approximately 2, 6, 17, and 42 times the highest recommended human dose, respectively, based on body surface area) were used. In the 2-year rat carcinogenicity study, lubiprostone doses of 20, 100, and 400 mcg/kg/day (approximately 3, 17, and 68 times the highest recommended human dose, respectively, based on body surface area) were used. In the mouse carcinogenicity study, there was no significant increase in any tumor incidences. There was a significant increase in the incidence of interstitial cell adenoma of the testes in male rats at the 400 mcg/kg/day dose. In female rats, treatment with lubiprostone produced hepatocellular adenoma at the 400 mcg/kg/day dose.
- Mutagenesis
- Lubiprostone was not genotoxic in the in vitro Ames reverse mutation assay, the in vitro mouse lymphoma (L5178Y TK +/) forward mutation assay, the in vitro Chinese hamster lung (CHL/IU) chromosomal aberration assay, and the in vivo mouse bone marrow micronucleus assay.
- Impairment of Fertility
- Lubiprostone, at oral doses of up to 1000 mcg/kg/day, had no effect on the fertility and reproductive function of male and female rats. However, the number of implantation sites and live embryos were significantly reduced in rats at the 1000 mcg/kg/day dose as compared to control. The number of dead or resorbed embryos in the 1000 mcg/kg/day group was higher compared to the control group, but was not statistically significant. The 1000 mcg/kg/day dose in rats is approximately 169 times the highest recommended human dose of 48 mcg/day, based on body surface area.

# Clinical Studies
- Chronic Idiopathic Constipation
- Two double-blinded, placebo-controlled studies of identical design were conducted in patients with chronic idiopathic constipation. Chronic idiopathic constipation was defined as, on average, less than 3 spontaneous bowel movements (SBMs) per week (a SBM is a bowel movement occurring in the absence of laxative use) along with one or more of the following symptoms of constipation for at least 6 months prior to randomization: 1) very hard stools for at least a quarter of all bowel movements; 2) sensation of incomplete evacuation following at least a quarter of all bowel movements; and 3) straining with defecation at least a quarter of the time.
- Following a 2-week baseline/washout period, a total of 479 patients (mean age 47.2  years; 88.9% female; 80.8% Caucasian, 9.6% African American, 7.3% Hispanic, 1.5% Asian; 10.9%  65 years of age) were randomized and received Amitiza 24 mcg twice daily or placebo twice daily for 4 weeks. The primary endpoint of the studies was SBM frequency. The studies demonstrated that patients treated with Amitiza had a higher frequency of SBMs during Week 1 than the placebo patients. In both studies, results similar to those in Week 1 were also observed in Weeks 2, 3, and 4 of therapy (Table 5).
- In both studies, Amitiza demonstrated increases in the percentage of patients who experienced SBMs within the first 24 hours after administration when compared to placebo (56.7% vs. 36.9% in Study 1 and 62.9% vs. 31.9% in Study 2, respectively). Similarly, the time to first SBM was shorter for patients receiving Amitiza than for those receiving placebo.
- Signs and symptoms related to constipation, including abdominal bloating, abdominal discomfort, stool consistency, and straining, as well as constipation severity ratings, were also improved with Amitiza versus placebo. The results were consistent in subpopulation analyses for gender, race, and elderly patients ( 65 years of age).
- During a 7-week randomized withdrawal study, patients who received Amitiza during a 4-week treatment period were then randomized to receive either placebo or to continue treatment with Amitiza. In Amitiza-treated patients randomized to placebo, SBM frequency rates returned toward baseline within 1 week and did not result in worsening compared to baseline. Patients who continued on Amitiza maintained their response to therapy over the additional 3 weeks of treatment.
- Opioid-induced Constipation
- The efficacy of Amitiza in the treatment of opioid-induced constipation in patients receiving opioid therapy for chronic, non-cancer-related pain was assessed in three randomized, double-blinded, placebo-controlled studies. In Study 1, the median age was 52 years (range 2082) and 63.1% were female. In Study 2, the median age was 50 years (range 2177) and 64.4% were female. In Study 3, the median age was 50 years (range 2189) and 60.1% were female. Patients had been receiving stable opioid therapy for at least 30 days prior to screening, which was to continue throughout the 12-week treatment period. At baseline, mean oral morphine equivalent daily doses (MEDDs) were 99 mg and 130 mg for placebo-treated and Amitiza-treated patients, respectively, in Study 1. Baseline mean MEDDs were 237 mg and 265 mg for placebo-treated and Amitiza-treated patients, respectively, in Study 2. In Study 3, baseline mean MEDDs were 330 mg and 373 mg for placebo-treated and Amitiza-treated patients, respectively. The Brief Pain Inventory-Short Form (BPI-SF) questionnaire was administered to patients at baseline and monthly during the treatment period to assess pain control. Patients had documented opioid-induced constipation at baseline, defined as having less than 3 spontaneous bowel movements (SBMs) per week, with at least 25% of SBMs associated with one or more of the following conditions: (1) hard to very hard stool consistency; (2) moderate to very severe straining; and/or (3) having a sensation of incomplete evacuation. Laxative use was discontinued at the beginning of the screening period and throughout the study. With the exception of the 48-hour period prior to first dose and for at least 72 hours (Study 1) or 1 week (Study 2 and Study 3) following first dose, use of rescue medication was allowed in cases where no bowel movement had occurred in a 3-day period. Median weekly SBM frequencies at baseline were 1.5 for placebo patients and 1.0 for Amitiza patients in Study 1 and, for both Study 2 and Study 3, median weekly SBM frequencies at baseline were 1.5 for both treatment groups.
- In Study 1, patients receiving non-diphenylheptane (e.g., non-methadone) opioids (n = 431) were randomized to receive placebo (n = 217) or Amitiza 24 mcg twice daily (n = 214) for 12 weeks. The primary efficacy analysis was a comparison of the proportion of overall responders in each treatment arm. A patient was considered an overall responder if 1 SBM improvement over baseline were reported for all treatment weeks for which data were available and 3 SBMs/week were reported for at least 9 of 12 treatment weeks. The proportion of patients in Study 1 qualifying as an overall responder was 27.1% in the group receiving Amitiza 24 mcg twice daily compared to 18.9% of patients receiving placebo twice daily (treatment difference = 8.2%; p-value = 0.03). Examination of gender and race subgroups did not identify differences in response to Amitiza among these subgroups. There were too few elderly patients ( 65 years of age) to adequately assess differences in effects in that population.
- In Study 2, patients receiving opioids (N = 418) were randomized to receive placebo (n = 208) or Amitiza 24 mcg twice daily (n = 210) for 12 weeks. Study 2 did not exclude patients receiving diphenylheptane opioids (e.g., methadone). The primary efficacy endpoint was the mean change from baseline in SBM frequency at Week 8; 3.3 vs. 2.4 for Amitiza and placebo-treated patients, respectively; treatment difference = 0.9; p-value = 0.004. The proportion of patients in Study 2 qualifying as an overall responder, as prespecified in Study 1, was 24.3% in the group receiving Amitiza compared to 15.4% of patients receiving placebo. In the subgroup of patients in Study 2 taking diphenylheptane opioids (baseline mean  MEDDs of 691  mg and 672  mg for placebo and Amitiza patients, respectively), the proportion of patients qualifying as an overall responder was 20.5% (8/39) in the group receiving Amitiza compared to 6.3% (2/32) of patients receiving placebo. Examination of gender and race subgroups did not identify differences in response to Amitiza among these subgroups. There were too few elderly patients ( 65 years of age) to adequately assess differences in effects in that population.
- In Study 3, patients receiving opioids (N = 451) were randomized to placebo (n = 216) or Amitiza 24 mcg twice daily (n = 235) for 12 weeks. Study 3 did not exclude patients receiving diphenylheptane opioids (e.g., methadone). The primary efficacy endpoint was the change from baseline in SBM frequency at Week 8. The study did not demonstrate a statistically significant improvement in SBM frequency rates at Week 8 (mean change from baseline of 2.7 vs. 2.5 for Amitiza and placebo-treated patients, respectively; treatment difference = 0.2; p-value = 0.76). The proportion of patients in Study 3 qualifying as an overall responder, as prespecified in Study 1, was 15.3% in the patients receiving Amitiza compared to 13.0% of patients receiving placebo. In the subgroup of patients in Study 3 taking diphenylheptane opioids (baseline mean  MEDDs of 730  mg and 992  mg for placebo and Amitiza patients, respectively), the proportion of patients qualifying as an overall responder was 2.1% (1/47) in the group receiving Amitiza compared to 12.2% (5/41) of patients receiving placebo.
- Irritable Bowel Syndrome with Constipation
- Two double-blinded, placebo-controlled studies of similar design were conducted in patients with IBS-C. IBS was defined as abdominal pain or discomfort occurring over at least 6 months with two or more of the following: 1) relieved with defecation; 2) onset associated with a change in stool frequency; and 3) onset associated with a change in stool form. Patients were sub-typed as having IBS-C if they also experienced two of three of the following: 1)  25% hard stools, and 3) > 25% SBMs associated with straining.
- Following a 4-week baseline/washout period, a total of 1154 patients (mean age 46.6  years; 91.6% female; 77.4% Caucasian, 13.2% African American, 8.5% Hispanic, 0.4% Asian; 8.3%  65 years of age) were randomized and received Amitiza 8 mcg twice daily (16 mcg/day) or placebo twice daily for 12 weeks. The primary efficacy endpoint was assessed weekly utilizing the patient's response to a global symptom relief question based on a 7-point, balanced scale ("significantly worse" to "significantly relieved"): "How would you rate your relief of IBS symptoms (abdominal discomfort/pain, bowel habits, and other IBS symptoms) over the past week compared to how you felt before you entered the study?"
- The primary efficacy analysis was a comparison of the proportion of "overall responders" in each arm. A patient was considered an "overall responder" if the criteria for being designated a "monthly responder" were met in at least 2 of the 3 months on study. A "monthly responder" was defined as a patient who had reported "significantly relieved" for at least 2 weeks of the month or at least "moderately relieved" in all 4 weeks of that month. During each monthly evaluation period, patients reporting "moderately worse" or "significantly worse" relief, an increase in rescue medication use, or those who discontinued due to lack of efficacy, were deemed non-responders.
- The percentage of patients in Study 1 qualifying as an "overall responder" was 13.8% in the group receiving Amitiza 8 mcg twice daily compared to 7.8% of patients receiving placebo twice daily. In Study 2, 12.1% of patients in the Amitiza 8 mcg group were "overall responders" versus 5.7% of patients in the placebo group. In both studies, the treatment differences between the placebo and Amitiza groups were statistically significant.
- Results in men: The two randomized, placebo-controlled, double-blinded studies comprised 97 (8.4%) male patients, which is insufficient to determine whether men with IBS-C respond differently to Amitiza from women.
- During a 4-week randomized withdrawal period following Study 1, patients who received Amitiza during the 12-week treatment period were re-randomized to receive either placebo or to continue treatment with Amitiza. In Amitiza-treated patients who were overall responders during Study 1 and who were re-randomized to placebo, SBM frequency rates did not result in worsening compared to baseline.

# How Supplied
- Amitiza is available as an oval, soft gelatin capsule containing 8 mcg or 24 mcg of lubiprostone with "SPI" printed on one side. Amitiza is available as follows:
- 8 mcg pink capsule
Bottles of 60 (NDC 64764-080-60)
- Bottles of 60 (NDC 64764-080-60)
- 24 mcg orange capsule
Bottles of 60 (NDC 64764-240-60)
Bottles of 100 (NDC 64764-240-10)
- Bottles of 60 (NDC 64764-240-60)
- Bottles of 100 (NDC 64764-240-10)
- Store at 25C (77F); excursions permitted to 15 to 30C (59 to 86F).
- Protect from light and extreme temperatures.

## Storage
There is limited information regarding Lubiprostone Storage in the drug label.

# Images

## Drug Images

## Package and Label Display Panel

# Patient Counseling Information
- Physicians and patients should periodically assess the need for continued therapy.
- Nausea, Dyspnea or Diarrhea
- Instruct patients to take Amitiza twice daily with food and water to reduce the occurrence of nausea. Patients taking Amitiza may experience dyspnea within an hour of the first dose. Dyspnea generally resolves within 3 hours, but may recur with repeat dosing. Patients on treatment who experience severe nausea, dyspnea, or diarrhea should notify their physician.
- Nursing Mothers
- Advise lactating women to monitor their human milk-fed infants for diarrhea while taking Amitiza.

# Precautions with Alcohol
- Alcohol-Lubiprostone interaction has not been established. Talk to your doctor about the effects of taking alcohol with this medication.

# Brand Names
- Amitiza

# Look-Alike Drug Names
There is limited information regarding Lubiprostone Look-Alike Drug Names in the drug label.

# Drug Shortage Status

# Price