Wattanaporn Abramowitz

Deposition and pharmacokinetics of flunisolide delivered from pressurized inhalers containing non-CFC and CFC propellants.

Our objective was to assess the deposition and pharmacokinetics of a novel formulation of flunisolide (Aerobid, Forest Laboratories) in hydrofluoroalkane (HFA) 134a delivered by pressurized metered dose inhaler (pMDI). The design was a two-way crossover investigation in 12 healthy male subjects comparing HFA-134a flunisolide by pMDI versus pMDI plus 50 mL spacer device. Four of these subjects also took part in a two-way crossover investigation comparing chlorofluorocarbon (CFC) flunisolide pMDI versus pMDI plus Aerochamber holding chamber. The imaging technique of gamma scintigraphy was used to quantify total and regional lung deposition of flunisolide. Plasma levels of flunisolide and its major metabolite (6beta-OH flunisolide) were also determined. The spacer and Aerochamber reduced oropharyngeal deposition dramatically for both the HFA and CFC products (mean 59.8 to 14.9% (p < 0.01) of ex-valve (metered) dose for HFA product; 66.3 to 12.3% (p < 0.01) of ex-valve dose for CFC product) owing to deposition of part of the dose on the walls of the add-on devices themselves. Lung deposition averaged 22.6 and 40.4% (p < 0.01) of the ex-valve dose for the HFA formulation used with pMDI alone and with pMDI plus spacer. Mean lung deposition of the CFC formulation delivered via the Aerochamber (mean 23.4%) was higher than that for the CFC pMDI alone (mean 17.0%), but this difference was not statistically significant. Lung deposition expressed as percentage ex-device (delivered) dose averaged 68.3% for HFA pMDI plus spacer and 19.7% for CFC pMDI. Plasma levels of flunisolide were higher for the pMDI plus spacer than for pMDI alone, reflecting higher lung deposition via the spacer, but plasma levels of the 6beta-OH flunisolide metabolite were higher for the pMDI alone as a consequence of higher oropharyngeal deposition. When delivered via the spacer, pulmonary targeting of the flunisolide HFA formulation was improved compared with the CFC formulation, which should benefit patients by providing satisfactory asthma therapy from a much-reduced delivered dose of flunisolide.

An evaluation of the potential for pharmacokinetic interaction between escitalopram and the cytochrome P450 3A4 inhibitor ritonavir

BACKGROUND Depression often coexists with a number of disease states, and patients with a diagnosis of depression often receive multiple medications. Thus, it is desirable to avoid coadministration of agents that have a potential for drug interactions in these patients. Although escitalopram and its metabolites are weak to negligible inhibitors of the cytochrome P450 (CYP) 3A4 isozyme and are therefore unlikely to affect plasma concentrations of ritonavir (a CYP3A4 substrate and prototype CYP3A4 inhibitor), ritonavir may potentially affect plasma concentrations of escitalopram, as CYP3A4 is partially responsible for conversion of escitalopram to its major metabolite, S-demethylcitalopram (S-DCT). OBJECTIVES The aim of this study was to investigate the potential for pharmacokinetic interaction between escitalopram and ritonavir after concomitant administration of a single dose of each in healthy young subjects. METHODS In this single-center, randomized, open-label, 3-way crossover study, subjects received each of the following: a single dose of escitalopram 20 mg, a single dose of ritonavir 600 mg, and single doses of both escitalopram 20 mg and ritonavir 600 mg. Blood was collected and plasma was analyzed for the pharmacokinetic parameters (maximum plasma concentration [C(max)], time to C(max) [T(max)], area under the plasma concentration-time curve, plasma elimination half-life, oral clearance, and apparent volume of distribution) of escitalopram, S-DCT, and ritonavir. RESULTS Of 21 subjects (11 men, 10 women; mean [SD] age, 28.4 [4.4] years) who were enrolled, 18 completed the study. After concomitant administration of escitalopram and ritonavir, no statistically significant differences were noted in the pharmacokinetics of escitalopram, with the exception of apparent volume of distribution, which was reduced by approximately 10% (P < 0.001). The pharmacokinetics of S-DCT were unaffected by coadministration of ritonavir, with the exception of T(max), which was increased in the presence of ritonavir. The pharmacokinetic parameters of ritonavir were also unaffected by coadministration of escitalopram. CONCLUSION In general, no pharmacokinetic interaction was observed between escitalopram and ritonavir in the present study.

Steady-State Pharmacokinetics of Citalopram in Young and Elderly Subjects

Study Objectives. To compare the steady‐state pharmacokinetics of citalopram after multiple‐dose administration in elderly and young subjects, and to correlate pharmacokinetic measurements with tolerability.

Pharmacokinetic comparison of oral solution and tablet formulations of citalopram: a single-dose, randomized, crossover study.

BACKGROUND Citalopram tablets fulfill most dosing needs in the treatment of depression, but some patients may have difficulty swallowing tablets and thus may be less likely to comply with their medication regimen. A liquid formulation of citalopram could be beneficial for such patients. OBJECTIVE This study was undertaken to compare the pharmacokinetic profiles of oral solution and tablet formulations of citalopram in healthy volunteers. METHODS In this open-label, single-dose, randomized, crossover, bioequivalence study, healthy volunteers alternately received one 60-mg dose of citalopram as an oral solution (10 mg/5 mL) and one 60-mg dose as a tablet. Doses were separated by a 14-day interval. RESULTS Of 24 subjects enrolled (mean age 27 years), 24 (16 men and 8 women) received the citalopram oral solution and 23 (15 men and 8 women) received the tablet; 1 subject discontinued before receiving the tablet. Citalopram was rapidly absorbed, with peak plasma concentrations occurring at approximately 4 hours with both formulations. The rate and extent of absorption were similar between the 2 formulations, and no statistically significant differences were observed in half-life or oral clearance between formulations. Similarly, the pharmacokinetic profile for demethylcitalopram (the major metabolite of citalopram) did not differ between the 2 formulations. Both formulations were well tolerated, with no serious adverse events reported. CONCLUSION The oral solution and tablet formulations of citalopram 60 mg were determined to be bioequivalent in this population.

Lack of effect of a single dose of ketoconazole on the pharmacokinetics of citalopram.

Study Objective. To determine whether the pharmacokinetics of the antidepressant citalopram are affected by ketoconazole, a potent inhibitor of cytochrome P450 (CYP) 3A4.

Lack of interaction between citalopram and the CYP3A4 substrate triazolam.

Study Objectives. To determine the effect of the selective serotonin reuptake inhibitor citalopram on plasma levels of triazolam, and to determine the effect of a single dose of triazolam on steady‐state levels of citalopram and its major metabolites.