Please select the eligibility criteria that correspond to the clinical trial below.
Title: Efficacy of Antidepressants in Chronic Back Pain
Brief Summary: The purpose of this study is to determine whether gabapentin is efficacious as an analgesic for chronic low back pain.


Options:
A: Inclusion Criteria:

* Must be resident of the county of San Diego, California
* Ages 21-70 inclusive
* Low back pain (T-6 or below, secondary to degenerative disk or degenerative joint disease) present "on a daily basis" for the previous 6 months or longer, of at least "moderate" intensity determined by Descriptor Differential Scale (DDS) \> 7
* English-speaking, literate, able to understand the study and communicate with the study team
* Presently not a candidate for back surgery (one prior back surgery permitted if it was \> 5 years ago and resulted in complete relief)
* Discontinued muscle relaxants, anticonvulsants, antidepressants, and opioids at least two weeks before screening and agree to discontinue throughout study (can remain on stable dose of NSAIDs)
* If female, not pregnant or lactating; agrees to use reliable contraception throughout the study, and has negative pregnancy test at screening
* Gives informed consent.

Exclusion Criteria:

* A major coexisting medical illness (e.g., diabetes, renal or hepatic disease, chronic obstructive pulmonary disease, cancer, or class III or IV organic heart disease) that might increase risks of gabapentin, or major surgical or non-surgical intervention for any disorder within the past 12 months, since rehabilitation from treatment may confound study outcomes
* Significant coexisting orthopedic or pain problems; sciatica (pain, weakness, or dysesthesia solely in distribution of a lumbar spinal nerve, with or without reflex change) or back pain due to other disorders (e.g., fibromyalgia, vertebral fracture, osteomyelitis, metastatic cancer, rheumatoid arthritis; spinal stenosis)
* Diagnostic and Statistical Manual (DSM)-IV diagnosis of alcohol or other substance abuse or dependence (within the previous 12 months or positive urine toxicology at screening), current major depression or dysthymia; or lifetime bipolar disorder (I or II) (excluded because gabapentin is antidepressive and antimanic); or major anxiety disorder (e.g., panic disorder; or psychosis; or lifetime presence of cognitive impairment disorder (e.g. dementia)
* History of multiple adverse drug reactions or known allergy to gabapentin
* Use of psychotropics (e.g., antidepressants, anxiolytics), which would need to be continued during the study, or other drugs or agents (i.e., herbal preparations) which might interact with the study drug
* Prior treatment with the study drug
* Use of systemic corticosteroids or corticosteroid injections within three months of screening; or concurrent behavioral therapies, chiropractic treatment, or transcutaneous electrical nerve stimulation unit
* Renal impairment (creatinine \> 1.8 mg/dL)
* Hepatic impairment (bilirubin \> 1.5 X upper normal limit, or aspartate aminotransferase (AST) or alanine transaminase (ALT) \> 2 X upper normal limit)
* Hematologic abnormality (hemoglobin \< 9.4 gm/dL; absolute white blood cell (WBC) count \< 3000/mm3, platelets \< 100,000
* Pregnancy
* Immunosuppression
* Use of experimental drugs or participation in other clinical trials
B: Inclusion Criteria:

1. Male between 18 and 55 years of age inclusive, at the time of signing the informed consent.
2. Body weight ≥ 50 Kilogram (kg) and BMI within the range 18.5-29.9 Killogram per square meter (kg/m2) (inclusive).
3. Healthy as determined by a responsible and experienced physician, based on a medical evaluation including medical history, physical examination, psychiatric history, psychiatric evaluation, laboratory tests and cardiac monitoring.
4. Aspartate aminotransferase (AST), Alanine aminotransferase (ALT), alkaline phosphatase and bilirubin ≤ 1.5x Upper Limit of Normal (ULN)
5. QT duration corrected for heart rate by Bazett's formula (QTcB) or QT duration corrected for heart rate by Fridericia's formula (QTcF) \< 450 milli second (msec).

Exclusion Criteria:

1. The subject has either a previous disease or current medical condition, which as judged by the Investigator, may compromise safety or affect the interpretation of efficacy data.
2. History of known or suspected seizures, including infantile febrile, unexplained significant and recent loss of consciousness or history of significant head trauma with loss of consciousness or a family history (first degree relative) of epilepsy or seizures (fits).
3. Abnormalities in 12-lead Electrocardiogram (ECG)
4. Systolic blood pressure (BP) below 90 or above 160mm Hg, or diastolic blood pressure below 50 or above 100 millimeters of mercury (mmHg).
5. History of sensitivity to any of the study medications
6. History of regular alcohol consumption within 6 months of the study defined as: an average weekly intake of \>21 units. One unit is equivalent to 8 g of alcohol: a half-pint (\~240 millil litre \[ml\]) of beer, 1 glass (125 ml) of wine or 1 (25 ml) measure of spirits.
7. A positive pre-study drug/alcohol screen at the screening visit.
8. Excessive caffeine drinkers (\~5 or more cups a day) .
9. Excessive smokers (\>5 /day)
10. Use of prescription or non-prescription drugs, including vitamins, herbal and dietary supplements (including St John's Wort) within 7 days (or 14 days if the drug is a potential enzyme inducer) or 5 half-lives (whichever is longer) prior to screening, unless in the opinion of the Investigator and GSK Medical Monitor the medication will not interfere with the study procedures or compromise subject safety.
11. Use of any topical steroid or capsaicin preparations in the previous 30 days to screening, unless in the opinion of the Investigator and GSK Medical Monitor the medication will not interfere with the study procedures or compromise subject safety.
12. The subject is needle phobic
13. The subject is unable to tolerate the electrical hyperalgesia model or nerve stimulation, including anxiety or atypical response to the stimulation on the training at the screening visit.
14. The subject does not produce an area of allodynia or hyperalgesia to the electrical hyperalgesia model during the screening session.
15. Subject who, in the investigator/designee's judgement, poses a significant suicide risk. Evidence of serious suicide risk may include any history of suicidal behaviour and/or any evidence of suicidal ideation on any questionnaires e.g. type 4 or 5 on the C-SSRS in the last 6 months.
16. The subject has participated in a clinical trial and has received an investigational product within the following time period prior to the baseline session in the current study: 90 days, 5 half-lives or twice the duration of the biological effect of the investigational product (whichever is longer).
17. Where participation in the study would result in donation of blood or blood products in excess of 500 mL within a 84 day period.
18. A positive pre-study Hepatitis B surface antigen or positive Hepatitis C antibody result within 3 months of screening
19. Unwillingness or inability to follow the procedures outlined in the protocol.
C: Inclusion Criteria:

1. Men or women 18 years or older who have experienced pain for at least 6 months, but not more than 5 years after the healing of a herpes zoster skin rash(typically about 4 months after the rash first appears).
2. Patient has a pain intensity score of at least 4 on the 11-point Numerical Rating Scale (NRS). Patients should never be informed of the pain intensity criterion prior to screening or randomization.
3. Patients of child-bearing potential must have a negative serum pregnancy test at screening and a negative follow-up urine pregnancy test at randomization.
4. Patient has a mean baseline week pain intensity score of at least 4 on the 11-point NRS scale at the end of a 1-week baseline period and has completed at least 4 days of daily pain diary entries during the baseline week.
5. Patients must have a minimum washout period of greater than 5 times the half-life of the drug of several medications.
6. Patients currently treated with gabapentin pr pregabalin at screening may be eligible for the study, but must have a tapering period wherein the dose of gabapentin or pregabalin is reduced gradually over a period of 5 days followed by a two day washout prior to the Baseline Week.

Exclusion Criteria:

1. Patients who have previously not responded to treatment for PHN with gabapentin or pregabalin.
2. Patients who previously experienced dose-limiting adverse effects that prevented titration of gabapentin to an effective dose.
3. Patient is a nursing mother.
4. Patient has hypersensitivity to gabapentin.
5. Patient has had neurolytic or neurosurgical treatment for PHN.
6. Patient has severe pain from causes other than PHN.
7. Patient has used injected anesthetics or steroids within 30 days of baseline.
8. Patient has skin conditions in the area affected by the neuropathy that could alter sensation.
9. Patient is in an immunocompromised state.
10. Patient has an estimated creatinine clearance less than 50 ml/min.
11. Patient has had malignancy within past 2 years other than basal cell carcinoma.
12. Patient has had gastric reduction surgery.
13. Patient has severe chronic diarrhea, chronic constipation \[unless attributed to drugs that will be washed out\], uncontrolled irritable bowel syndrome (IBS) or unexplained weight loss.
14. Patient has any abnormal chemistry or hematology results that are deemed by the investigator to be clinically significant.
15. Patient has a history of substance abuse within the past year.
16. Patient has a history of seizure (except for infantile febrile seizure) or is at risk of seizure due to head trauma.
17. Patient has a history of chronic hepatitis B or C, hepatitis within the past 3 months, or HIV infection.
18. Patient has any other clinically significant medical or psychological condition that, in the opinion of the Investigator would jeopardize the safety of the patient or affect the validity of the study results.
19. Continuing use of any concomitant medication excluded by Inclusion Criterion 5.
20. Patient has participated in a clinical trial of an investigational drug or device within 30 days of the screening visit.
D: Inclusion Criteria:

1. Men or women 18 years or older who have experienced pain for at least 3 months after the healing of a herpes zoster skin rash (typically about 4 months after the rash first appears).
2. Patient has pain intensity score of at least 4 on the 11-point Likert numerical rating scale at screening. Potential patients should not be informed of the pain intensity eligibility criterion prior to screening or randomization.
3. Patients of childbearing potential must have a negative urine pregnancy test at screening/randomization, and must use medically acceptable methods of birth control. Acceptable methods of birth control include oral or transdermal contraceptives, condom, spermicidal foam, intrauterine device (IUD), progestin implant or injection, abstinence, vaginal ring, or sterilization of partner. The reason for non-childbearing potential, such as bilateral tubal ligation, bilateral oophorectomy, hysterectomy, or postmenopausal for ≥ 1 year, must be specified in the patient's case report form (CRF).
4. Patient has a mean baseline week pain intensity score of at least 4 on the 11-point Likert scale at the end of a 1-week pre-treatment period and has completed at least 4 days of daily pain diary entries during the baseline week.
5. Patient must have a minimum washout period of greater than 5 times the half-life of the drug of any of the following medications: benzodiazepines, skeletal muscle relaxants, orally administered steroids, capsaicin, mexiletene, centrally acting analgesics (dextromethorphan, tramadol), opiates, topical lidocaine, anticonvulsants and serotonin and norepinephrine reuptake inhibitors (SNRIs). Anticonvulsants, SNRIs, opiates and benzodiazepines should be tapered appropriately, using product label instructions as a guide.
6. Patients currently treated with gabapentin or pregabalin at screening may be eligible for the study, but must have a tapering period wherein the dose of gabapentin or pregabalin is reduced gradually over a period of at least 7 days plus a 2-day or 3-day washout of gabapentin or pregabalin, respectively, prior to start of the baseline week.

Exclusion Criteria:

1. Patients who have previously not responded to treatment for PHN with gabapentin at doses of ≥ 1200 mg/day or pregabalin at doses ≥ 300 mg/day.
2. Patients who previously experienced dose-limiting adverse effects that prevented titration of gabapentin to an effective dose.
3. Patient is a nursing mother.
4. Patient has hypersensitivity to gabapentin.
5. Patient has had neurolytic or neurosurgical treatment for PHN.
6. Patient has severe pain from causes other than PHN.
7. Patient has used injected anesthetics or steroids within 30 days of baseline.
8. Patient has skin conditions in the area affected by the neuropathy that could alter sensation.
9. Patient is in an immunocompromised state.
10. Patient has an estimated creatinine clearance of \< 60 ml/min calculated using the Cockroft Gault method. If the patient fails this criterion, the Investigator may decide to conduct a 24-hour creatinine clearance test. The patient would be allowed to enroll in the study if the 24-hour test result is \< 60 ml/min.
11. Patient has had a malignancy within the past 2 years other than basal cell carcinoma.
12. Patient has had gastric reduction surgery.
13. Patient has severe chronic diarrhea, chronic constipation \[unless attributed to drugs that will be washed out\], uncontrolled irritable bowel syndrome (IBS) or unexplained weight loss.
14. Patient has any abnormal chemistry or hematology results that are deemed by the Investigator to be clinically significant.
15. Patient has a history of substance abuse within the past year.
16. Patient has a history of seizure (except for infantile febrile seizure) or is at risk of seizure due to head trauma.
17. Patient has a history of chronic hepatitis B or C, hepatitis within the past 3 months, or HIV infection.

Answer: A