Pharmacokinetics and Clinical Response of Tolvaptan in Neurocritical Care Patients

Study Overview
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Brief Summary
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To assess the pharmacokinetic profile of tolvaptan in critically ill acute brain injury patients and to secondarily evaluate the clinical response and safety of tolvaptan in acute brain injured patients

Official Title
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Pharmacokinetics and Clinical Response of Tolvaptan in Neurocritical Care Patients

Conditions
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Brain Injury, Hyponatremia

Intervention / Treatment
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* Drug: Tolvaptan


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Acute brain injury patients in the ICU with hyponatremia (Na < 135 mmol/L) necessitating treatment in addition to fluid restriction per clinical judgement or patients at risk for worsening cerebral edema Informed consent obtained from patient or authorized legal representative Age ≥ 18 years Exclusion Criteria: Use of CYP3A4 inhibitors or inducers as medications, juices, or herbal supplements within 96 hours prior to the study period. A positive urine or serum pregnancy test, or are currently breast-feeding Patients with subarachnoid hemorrhage or in patients suspected to have cerebral salt wasting or any signs of volume depletion Imminent death or brain death Concomitant fungal infection History of HIV Concomitant administration of continuous infusion hypertonic saline, conivaptan or hypertonic saline bolus within 24 hours of study drug administration Diuretic or mannitol administration within 6 hours Serum creatinine ≥ 3.5 mg/dL Diagnosis of cirrhosis or liver function tests > 2x the upper limit of normal

Ages Eligible for Study
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Minimum Age: 18 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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No

Study Plan
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How is the study designed?
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Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Brain injured patients with hyponatremia<br>Patients with acute brain injury who develop hyponatremia and are administered tolvaptan via the nasogastric tube, deemed necessary by the primary medical team. | Drug: Tolvaptan<br> <br> |

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Maximum observed plasma concentration (Cmax) and time to maximum observed plasma concentration (Tmax) of tolvaptan over 36 hours post-dose | Cmax will be derived from plasma concentrations versus time using a validated LS/MS/MS assay is sodium heparinized plasma. The tolvaptan assay has a range of 1.00 - 200 mg/mL. Blood samples will be collected at 0, 0.5, 1, 1.5, 2, 3, 4, 6, 8, 12, 16, 20, 24, 30 and 36 hours after the dose of tolvaptan is administered. The first 15 patients will receive single dose 15mg of tolvaptan via a gastric tube and if determined not bioequivalent and no clinical response to oral administration and safe to administer, then last 15 patients will receive 30mg single dose via a gastric tube. | Over 36 hours from drug administration | 
| The elimination rate constant (ke) of tolvaptan over 36 hours post-dose | Ke derived from plasma concentrations versus time using a validated LS/MS/MS assay is sodium heparinized plasma. The tolvaptan assay has a range of 1.00 - 200 mg/mL. Blood samples will be collected at 0, 0.5, 1, 1.5, 2, 3, 4, 6, 8, 12, 16, 20, 24, 30 and 36 hours after the dose of tolvaptan is administered. The first 15 patients will receive single dose 15mg of tolvaptan via a gastric tube and if determined not bioequivalent and no clinical response to oral administration and safe to administer, then last 15 patients will receive 30mg single dose via a gastric tube. | Over 36 hours from drug administration | 
| Area under the plasma concentration time curve (AUC) of tolvaptan from time zero to 36 hours post-dose | AUC will be computed from 0 to 36 hours using the linear-log trapezoidal method and extrapolated to infinity. Tolvaptan concentrations will be determined using a validated LS/MS/MS assay is sodium heparinized plasma. The tolvaptan assay has a range of 1.00 - 200 mg/mL. Blood samples will be collected at 0, 0.5, 1, 1.5, 2, 3, 4, 6, 8, 12, 16, 20, 24, 30 and 36 hours after the dose of tolvaptan is administered. The first 15 patients will receive single dose 15mg of tolvaptan via a gastric tube and if determined not bioequivalent and no clinical response to oral administration and safe to administer, then last 15 patients will receive 30mg single dose via a gastric tube. | Over 36 hours from drug administration | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| The clinical response of tolvaptan administered through the nasogastric tube in acute brain injured patients | Clinical response is defined as a change in serum sodium of 4 - 6 mEq/L | Over 36 hours from drug administration | 
| The safety of tolvaptan administered via a nasogastric tube in acute brain injured patients | Safety assessments will include: vital signs, clinical laboratory tests, concomitant medications, and reported or observed adverse events. The rate of sodium correction will also be assessed. Excessive correction in sodium is defined as ≥ 12 mE/L increased in serum sodium within 24 hours of the dose. Excessive drop in blood pressure will be defined as >20% reduction in MAP from baseline. | Over 36 hours from drug administration |