Bioavailability and pharmacokinetic profile of a newly-developed twice-a-day sustained-release paracetamol formulation.

OBJECTIVE: A new twice daily sustained-release (SR) paracetamol formulation was developed to improve convenience and enhance patient compliance for treatment of pain from chronic diseases. This research aimed to evaluate bioavailability and compare pharmacokinetic (PK) properties of the new SR paracetamol formulation (2x1,000 mg) with those of immediate-release (IR) paracetamol (2x500 mg) and existing extended-release (ER) paracetamol (2x665 mg). METHODS: Two randomized, single-dose, 4-way crossover studies were conducted. A total of 28 healthy male and female volunteers participated in each study. The relative bioavailability, partial extent of absorption, overall elimination, food effect, and safety were evaluated. RESULTS: The estimates of relative bioavailability of new SR with IR formulation based on dose-adjusted AUC0-inf were 91% (0.86-0.96) for the fasted state and 99% (0.95-1.02) for the fed state, while these estimates comparing new SR with ER formulation were 99% (0.96-1.03) in the fasted state and 98% (0.95-1.02) in the fed state. The accumulated mean time period at or above the minimal therapeutic plasma paracetamol concentration for the new SR was from 90% to 112% longer than that of the IR formulation, in fasted and fed state, respectively. Food significantly increased Cmax of SR formulation, with ratios fast vs. fed 0.79 (p<0.0001) and 0.77 (p<0.0001) in study I and II, respectively. CONCLUSIONS: The new SR formulation was well absorbed, with more than 90% relative bioavailability as compared to the currently marketed IR and ER products and better sustained-release PK characteristics, which make it suitable for twice-daily paracetamol treatment.

Pharmacokinetic interactions between the hepatitis C virus protease inhibitor boceprevir and ritonavir-boosted HIV-1 protease inhibitors atazanavir, darunavir, and lopinavir.

BACKGROUND: Boceprevir represents a new treatment option for hepatitis C (HCV)-infected patients, including those with HCV/human immunodeficiency virus coinfection; however, little is known about pharmacokinetic interactions between boceprevir and antiretroviral drugs. METHODS: A randomized, open-label study to assess the pharmacokinetic interactions between boceprevir and ritonavir-boosted protease inhibitors (PI/r) was conducted in 39 healthy adults. Subjects received boceprevir (800 mg, 3 times daily) for 6 days and then received PI/r as follows: atazanavir (ATV) 300 mg once daily, lopinavir (LPV) 400 mg twice daily, or darunavir (DRV) 600 mg twice daily, each with ritonavir (RTV) 100 mg on days 10-31, plus concomitant boceprevir on days 25-31. RESULTS: Boceprevir decreased the exposure of all PI/r, with area under the concentration-time curve [AUC] from time 0 to the time of the last measurable sample geometric mean ratios of 0.65 (90% confidence interval [CI], .55-.78) for ATV/r; 0.66 (90% CI, .60-.72) for LPV/r, and 0.56 (90% CI, .51-.61) for DRV/r. Coadministration with boceprevir decreased RTV AUC during a dosing interval τ (AUC(τ)) by 22%-36%. ATV/r did not significantly affect boceprevir exposure, but boceprevir AUC(τ) was reduced by 45% and 32% when coadministered with LPV/r and DRV/r, respectively. Overall, treatments were well tolerated with no unexpected adverse events. CONCLUSIONS: Concomitant administration of boceprevir with PI/r resulted in reduced exposures of PI and boceprevir. These drug-drug interactions may reduce the effectiveness of PI/r and/or boceprevir when coadministered.