Single-dose and steady-state pharmacokinetics of fosinopril and fosinoprilat in patients with hepatic impairment

A sensitive and efficient LC-MS/MS method for the bioanalysis of fosinopril diacid from human plasma and its application for a bioequivalence study in humans

Fosinopril diacid is an angiotensin converting enzyme inhibitor with efficient antihypertensive action. It is an active metabolic product formed in the body from hydrolysis of its prodrug Fosinopril. A sensitive, rapid method with high recovery for Fosinopril diacid from human plasma was developed. Solid-phase extraction technique employing Waters Oasis SPE cartridges gave clean samples with very high recovery of 97%. The analyte along with its internal standard (Benazepril hydrochloride) were chromatographed on an XTerra RP₈ column (4.6 × 50 mm, 5 μm) using methanol-ammonium acetate buffer (10 mm; 90:10, v/v) as the mobile phase. A triple quadrupole mass spectrometer equipped with electrospray ionization source operated in the negative ion mode was used for detection. Multiple reaction monitoring scan mode was used for monitoring the transitions from m/z 434.00 → 237.15 for Fosinopril diacid and m/z 423.10 → 174.00 for Benazepril hydrochloride. Beer-Lambert's law was obeyed in the range of 0.50-1,500.00 ng/ml (r = 0.9993). The stability of the drugs in human plasma and in stock solution was proved by performing stability tests as per US Food and Drug Administration guidelines. The method was successfully applied for a bioequivalence study of Fosinopril diacid in 36 healthy, adult, male volunteers under fasting conditions.

Identification of metabolites of fosinopril produced by human and rat liver microsomes with liquid chromatography-mass spectrometry

Metabolic profiles of prodrug fosinopril and pharmacologically active metabolite fosinoprilat were studied using human or rat liver microsomes and S9 fractions. Metabolites were identified by ultra high-performance liquid chromatography/quadrupole time-of-flight mass spectrometry (UHPLC/Q-TOF-MS) using electrospray ionization in the positive and negative ion mode. They were characterized by accurate MS and MS/MS spectra and based on their different fragmentation pathways. With human liver microsomes fosinopril was metabolized via hydroxylation, glucuronidation, and hydrolysis to fosinoprilat. As expected the main metabolite was fosinoprilat and it was further hydroxylated and glucuronidated. However, these metabolites were not detected after incubation of fosinoprilat with human liver microsomes, indicating that metabolic reactions occur in sequence and fosinopril is hydrolyzed after glucuronidation or hydroxylation. With the developed UHPLC/Q-TOF-MS method once or twice hydroxylated fosinopril metabolites were detected for the first time and different regioisomers were separated. It was observed that the hydrolysis of fosinopril to fosinoprilat was more efficient with rat than with human liver microsomes, and therefore more hydroxylated fosinoprilat metabolites were detected when rat liver microsomes were used. Glucuronidation of fosinopril was not observed with rat liver microsomes.

Impact of Disease States on the Pharmacokinetics and Pharmacodynamics of Angiotensin-Converting Enzyme Inhibitors

The pharmacokinetics and pharmacodynamics of angiotensin-converting enzyme inhibitors (ACE) in elderly patients and patients with renal and hepatic impairment were examined, and a role for an AUC/EC50 ratio to guide dosing was evaluated. A Medline and International Pharmaceutical Abstracts search was used to identify human studies and abstracts. Relevant data were evaluated and summarized. Dosing regimens were compared using an AUC/EC50 ratio. Most studies evaluating ACE inhibitors in renal impairment report a strong linear correlation between creatine clearance and drug elimination. AUC and EC50 values for these drugs in elderly subjects appear similar to younger and hypertensive patients. There is increased AUC in some patients with hepatic impairment. Pharmacodynamic data are conflicting. Prolonged ACE inhibition is evident in renal impairment but not necessarily other disease states. ACE inhibitor dosing for hypertension is reasonable based on pharmacokinetics and EC50 values. Further individualization of therapy may improve outcomes, and using the threshold AUC/EC50 ratio may help guide appropriate dosing.

Cirrhosis does not affect the pharmacokinetics and pharmacodynamics of clopidogrel

Clopidogrel, a new platelet ADP receptor antagonist used for the prevention of vascular ischemic events, is converted to an active metabolite via the cytochrome P450 system. Patients with cirrhosis may not metabolize drugs normally and may, in addition, have a number of defects in the coagulation system. To assess the effect of cirrhosis on the pharmacokinetics and pharmacodynamics of clopidogrel, the authors performed an open-label, parallel-group study of 12 patients with Child-Pugh Class A or B cirrhosis and 12 matched controls. All 24 subjects received clopidogrel 75 mg PO QD for 10 days. Pharmacokinetics of clopidogrel and the major metabolite SR 26334 were analyzed on Days 1 and 10; pharmacodynamics were assessed by the inhibition of ADP-induced platelet aggregation and by bleeding time prolongation factor. Pharmacokinetic analysis of clopidogrel was limited due to low plasma concentrations arising from rapid hydrolysis to SR 26334. The Cmax at SS for clopidogrel was higher in cirrhotics than in normals. However, exposures to the metabolite SR 26334, as measured by AUC(tau), were comparable. At Day 10, there was not a statistically significant difference in mean inhibition of platelet aggregation (49.2% +/- 38.6% in cirrhotics vs. 66.7% +/- 7.5% in normals) or in bleeding time prolongation factor (1.64 +/- 0.49 in cirrhotics vs. 1.54 +/- 0.87 in normals) between groups. No significant adverse events, including bleeding events, were reported. In conclusion, there were no significant differences in the pharmacokinetics and pharmacodynamics of clopidogrel in this group of subjects with cirrhosis and matched normals. Therefore, no dosage adjustment of clopidogrel is required in patients with Child-Pugh Class A or B cirrhosis.

Fosinopril versus enalapril in the treatment of hypertension: a double-blind study in 195 patients

The new angiotensin-converting enzyme (ACE) inhibitor fosinopril was compared with the ACE inhibitor enalapril in a multicenter (n = 11), multinational (Denmark, Finland, Iceland, Norway, and Sweden), double-blind, randomized, parallel-group 24-week study in 195 patients with mild to moderate essential hypertension [supine diastolic blood pressure, (SDBP) > or = 95 to < or = 110 mm Hg]. After discontinuing all previous antihypertensive medication, patients were entered into a placebo lead-in period of 4-6 weeks, followed by 24 weeks of randomized treatment with the active compounds administered with a double-dummy technique. The dose of fosinopril was 20 mg, which could be increased to 40 mg after 8 weeks (average 25.6 mg); that of enalapril was 10 mg, which could be increased to 20 mg after 8 weeks (average 12.9 mg). Hydrochlorothiazide 12.5 mg could be added after 16 weeks and was administered to 27% of the patients in the fosinopril group and to 30% in the enalapril group. All drugs were administered once daily. Supine systolic BP (SSBP) decreased from 157 to 143 mm Hg in the fosinopril group (p < 0.01), and from 159 to 147 mm Hg in the enalapril group (p < 0.01). SSDP decreased from 100 to 89 mm Hg in the fosinopril group (p < 0.01) and from 100 to 92 mm Hg in the enalapril group (p < 0.01). Throughout the study period, fosinopril reduced SSBP and SDBP numerically more than did enalapril, by 0-3 mm Hg. Adverse events (AE) caused withdrawal of study medication in 8 patients in the fosinopril group and in 14 patients in the enalapril group (NS). The number of reported AE was not statistically different in the two groups. Inhibition of the ACE was assessed in a subgroup of patients (n = 26, 13 in each group). Fosinopril caused a greater inhibition of ACE at the doses used in the present study, which was statistically significant. Both fosinopril and enalapril caused statistically significant reductions in BP of a similar magnitude, and both agents were well tolerated. However, fosinopril was consistently numerically slightly more effective than enalapril in reducing BP. There were fewer withdrawals due to AE (NS) in the fosinopril group, and the overall recorded AE were fewer in the fosinopril group (NS).