No abstract

The objectives of the 3 phase I studies described herein were (1) to compare the pharmacokinetics of gabapentin delivered from a novel gastric-retentive dosage form vs an immediate-release formulation, (2) to assess the dose proportionality of the gastric-retentive extended-release formulation, and (3) to determine the effect of food on the pharmacokinetics of gabapentin delivered from this formulation. The time to reach maximum plasma concentration (t(max)) was extended for gabapentin delivered from the gastric-retentive extended-release formulation compared with the immediate-release formulation. A dose-related increase in both the maximum plasma concentration (C(max)) and the area under the plasma concentration-time curve (AUC) was observed as the gabapentin dose increased from 600 to 2400 mg. Fed status and increased fat content delayed t(max) and enhanced C(max) and AUC in proportion to the fat content. The pharmacokinetics of gabapentin delivered from this extended-release formulation allows a reduced dosing frequency while maintaining bioavailability and possibly diminishing the occurrence of adverse events attributable to a slower increase to the peak concentration compared with the immediate-release dosage form.

Glumetz (Depomed, Inc., Menlo Park, CA, USA) is a recently approved gastric retentive extended-release formulation of metformin (M-ER) that provides effective, sustained and well-tolerated glycemic control with once daily administration. Pharmacokinetic studies have demonstrated a similar bioavailability of M-ER administered once daily to immediate-release metformin given twice daily. In addition, M-ER has demonstrated a nearly linear dose proportionality with a relative bioavailability of highest dose to lowest dose of 80%, whereas with immediate-release metformin the relative bioavailability of the highest dose to the lowest dose is only 58%. M-ER demonstrated a positive food effect and should be administered with a meal, preferably the evening meal. Because metformin is only eliminated through renal mechanisms, the use of M-ER, as is the case with other formulations, is contraindicated in patients with renal impairment. Administration of M-ER with sulfonylureas (SUs) had no effect on the pharmacokinetics of metformin. In controlled clinical trials M-ER demonstrated efficacy for 24 weeks as a monotherapy or in combination with SU. Additionally, glycemic control was maintained for an extra 24 weeks in an open-label monotherapy extension study of M-ER. M-ER was well tolerated in all studies.

PurposeTo compare the aqueous humor (AH) and iris-ciliary body (ICB) concentration of bimatoprost in rabbit eyes treated with ISV-215 (0.03% bimatoprost formulated in DuraSite) with the marketed product bimatoprost 0.03% ophthalmic solution.MethodsThe left eye of rabbits received a single topical instillation of either ISV-215 (n = 32 eyes) or bimatoprost 0.03% (n = 32 eyes). At predetermined time points, levels of bimatoprost and bimatoprost acid in the AH and the ICB were quantified by HPLC-MS/MS.ResultsBoth bimatoprost and bimatoprost acid were detected in the AH and the ICB within 15 minutes of dosing. Bimatoprost acid concentrations in both compartments were markedly higher than bimatoprost. There was a statistically significant (P < 0.01) increase in the concentration of the prodrug in the AH and its acid form in the ICB in animals treated with ISV-215 compared to bimatoprost 0.03%. In the ISV-215-treated rabbit eyes, the highest concentrations of bimatoprost and bimatoprost acid were in the ICB and AH, respectively, while in the bimatoprost 0.03%-treated eyes, no differences in the drug content of the selected ocular tissues were observed.ConclusionsBimatoprost 0.03% formulated in DuraSite has superior ocular distribution and area under the curve compared to bimatoprost 0.03% in rabbit eyes. This improvement in the pharmacokinetic parameters of ISV-215 may provide us with a better platform to optimize a bimatoprost formulation that offers the same degree of efficacy in lowering intraocular pressure and improved therapeutic index in glaucomatous patients by lessening the ocular side effects associated with long-term use of topical prostaglandin F2α analogs.