Delavirdine clinical pharmacology

# Clinical Pharmacology

## Pharmacokinetics

### Absorption and Bioavailability
Delavirdine is rapidly absorbed following oral administration, with peak plasma concentrations occurring at approximately 1 hour. Following administration of delavirdine 400 mg 3 times daily (n = 67, HIV-1infected patients), the mean SD steady-state peak plasma concentration (Cmax) was 35  20 M (range: 2 to 100 M), systemic exposure (AUC) was 180  100 Mhr (range: 5 to 515 Mhr), and trough concentration (Cmin) was 15  10 M (range: 0.1 to 45 M). The single-dose bioavailability of delavirdine tablets relative to an oral solution was 85%  25% (n = 16, non-HIVinfected subjects). The single-dose bioavailability of delavirdine tablets (100-mg strength) was increased by approximately 20% when a slurry of drug was prepared by allowing delavirdine tablets to disintegrate in water before administration (n = 16, non-HIVinfected subjects). The bioavailability of the 200-mg strength delavirdine tablets has not been evaluated when administered as a slurry because they are not readily dispersed in water (see DOSAGE AND ADMINISTRATION).
Delavirdine may be administered with or without food. In a multiple-dose, crossover study, delavirdine was administered every 8 hours with food or every 8 hours, 1 hour before or 2 hours after a meal (n = 13, HIV-1infected patients). Patients remained on their typical diet throughout the study; meal content was not standardized. When multiple doses of delavirdine were administered with food, geometric mean Cmax was reduced by approximately 25%, but AUC and Cmin were not altered.

### Distribution
Delavirdine is extensively bound (approximately 98%) to plasma proteins, primarily albumin. The percentage of delavirdine that is protein-bound is constant over a delavirdine concentration range of 0.5 to 196 M. In 5 HIV-1infected patients whose total daily dose of delavirdine ranged from 600 to 1,200 mg, cerebrospinal fluid concentrations of delavirdine averaged 0.4%  0.07% of the corresponding plasma delavirdine concentrations; this represents about 20% of the fraction not bound to plasma proteins. Steady-state delavirdine concentrations in saliva (n = 5, HIV-1infected patients who received delavirdine 400 mg 3 times daily) and semen (n = 5 healthy volunteers who received delavirdine 300 mg 3 times daily) were about 6% and 2%, respectively, of the corresponding plasma delavirdine concentrations collected at the end of a dosing interval.

### Metabolism and Elimination
Delavirdine is extensively converted to several inactive metabolites. Delavirdine is primarily metabolized by cytochrome P450 3A (CYP3A), but in vitro data suggest that delavirdine may also be metabolized by CYP2D6. The major metabolic pathways for delavirdine are N-desalkylation and pyridine hydroxylation. Delavirdine exhibits nonlinear steady-state elimination pharmacokinetics, with apparent oral clearance decreasing by about 22-fold as the total daily dose of delavirdine increases from 60 to 1,200 mg/day. In a study of 14C-delavirdine in 6 healthy volunteers who received multiple doses of delavirdine tablets 300 mg 3 times daily, approximately 44% of the radiolabeled dose was recovered in feces, and approximately 51% of the dose was excreted in urine. Less than 5% of the dose was recovered unchanged in urine. The parent plasma half-life of delavirdine increases with dose; mean half-life following 400 mg 3 times daily is 5.8 hours, with a range of 2 to 11 hours.
In vitro and in vivo studies have shown that delavirdine reduces CYP3A activity and inhibits its own metabolism. In vitro studies have also shown that delavirdine reduces CYP2C9, CYP2D6, and CYP2C19 activity. Inhibition of hepatic CYP3A activity by delavirdine is reversible within 1 week after discontinuation of drug.

## Special Populations
- Hepatic or renal impairment: The pharmacokinetics of delavirdine in patients with hepatic or renal impairment have not been investigated (see PRECAUTIONS).
- Age: The pharmacokinetics of delavirdine have not been adequately studied in patients aged 65 years.
- Gender: Data from population pharmacokinetics suggest that the plasma concentrations of delavirdine tend to be higher in females than in males. However, this difference is not considered to be clinically significant.
- Race: No significant differences in the mean trough delavirdine concentrations were observed between different racial or ethnic groups.