Authors: Tam, S. William¹; Sabolinski, Michael L.¹; Worcel, Manuel¹; Packer, Milton²; Cohn, Jay N.³

Source: Clinical Pharmacokinetics, Volume 46, Number 10, 2007 , pp. 885-895(11)

Publisher: Adis International

Abstract:

Objective: To investigate whether the apparent discrepancy between the efficacy of the combination of isosorbide dinitrate (ISDN) and hydralazine demonstrated in the first V-HeFT trial (V-HeFT I) and that in V-HeFT II could be explained by pharmacokinetic differences in the study drug formulations, and to compare the pharmacokinetic profile of the fixed-dose combination of ISDN/hydralazine (FDC ISDN/HYD; BiDil^®) formulation used in A-HeFT with that of the V-HeFT study drug formulations.

Study participants and methods: A bioequivalence study was performed (n = 18-19 per group) comparing the ISDN and hydralazine formulations used in V-HeFT I, V-HeFT II and A-HeFT in healthy volunteer men and women aged 18-40 years. In phase A of the study, subjects received a reference solution of hydralazine hydrochloride/ISDN (37.5mg/10mg) orally. Slow acetylators were identified and randomised into three groups in phase B to receive a single oral dose of identical amounts of hydralazine hydrochloride/ISDN (37.5mg/10mg) from either (i) a hydralazine capsule plus an ISDN tablet (the V-HeFT I formulation); (ii) a hydralazine tablet plus an ISDN tablet (the V-HeFT II formulation); or (iii) FDC ISDN/HYD (the A-HeFT formulation). Blood/plasma concentrations of hydralazine and ISDN were determined from the blood samples taken between 0 and 36 hours.

Results: In phase B, the maximum observed concentrations (C_max) were 65.9 ± 53.9, 28.2 ± 15.8 and 51.5 ± 54.3 ng/mL of unchanged hydralazine, and 23.1 ± 12.3, 21.7 ± 13.4 and 26.7 ± 18.7 ng/mL of ISDN for the V-HeFT I, V-HeFT II and A-HeFT formulations, respectively. The area under the blood/plasma concentration-time curve (AUC) values were 32.6 ± 13.4, 23.3 ± 15.1 and 32.6 ± 18.5 ng · h/mL of hydralazine, and 24.4 ± 9.0, 24.8 ± 8.0 and 23.5 ± 6.3 ng · h/mL of ISDN for the V-HeFT I, V-HeFT II and A-HeFT formulations, respectively. For comparison of bioequivalence, the C_max and AUC were normalised to 65kg bodyweight, and point estimates and 90% confidence intervals of the C_max ratios, AUC ratios and ratios of the AUC in phase B normalised for clearance by the AUC in phase A (AUCR) were calculated. The three formulations were not bioequivalent based on the C_max and AUC comparisons.

Conclusions: The blood concentrations of hydralazine obtained with the tablet formulation tested in V-HeFT II were markedly lower than those obtained with the capsule formulation tested in V-HeFT I or the FDC ISDN/HYD single tablet used in A-HeFT. The apparently modest effect on survival observed in V-HeFT II could be explained in part by the poor hydralazine bioavailability of the tablet preparation used in this trial. ISDN exposures were similar in the two trials. The ISDN-hydralazine formulation used in V-HeFT II was not bioequivalent to the formulation used in V-HeFT I or to the FDC ISDN/HYD that had demonstrated a significant survival benefit in A-HeFT.

Keywords: Bioequivalence; Hydralazine; Hydralazine/isosorbide dinitrate; Isosorbide dinitrate

Document Type: Research article

Affiliations: 1: 1 NitroMed, Inc., Lexington, Massachusetts, USA 2: 2 University of Texas Southwestern Medical Center, Dallas, Texas, USA 3: 3 University of Minnesota, Minneapolis, Minnesota, USA

Publication date: 2007-01-01

Related content

• In this: publication
• By this: publisher
• In this Subject: Pharmacology
• By this author: Tam, S. William ;  Sabolinski, Michael L. ;  Worcel, Manuel ;  Packer, Milton ;  Cohn, Jay N.

Website © Publishing Technology. Article copyright remains with the publisher, society or author(s) as specified within the article.

• Terms and conditions
• Privacy policy
• Information for advertisers