Pharmacokinetic profile of a novel slow release preparation of molsidomine

Efficacy and safety of once- and twice-daily formulations of molsidomine in patients with stable angina pectoris: double-blind and open-label studies

Molsidomine, a sydnonimine acting as a heterocyclic direct nitric oxide donor, has been used for many years in several European countries for the treatment of patients with stable angina pectoris. The efficacy and tolerability of a novel once-daily 16-mg formulation of molsidomine (M16) were compared with those of the currently used twice-daily 8-mg molsidomine tablet (M8) in 666 patients. Study 1, a multicenter, randomized, double-blind, placebo-controlled, twin crossover study, involved 533 patients given acute and 2-week treatment with each drug formulation. Study 2, a multicenter, open-label, sequential, add-on trial, compared M16 and M8 in 133 patients. Drug effects on exercise capacity (study 1 only), frequency of anginal attacks and consumption of short-acting itroderivatives, and incidence of adverse events (AEs) were evaluated. Compared with placebo, M16 increased exercise capacity by 15% (P<.001) at the start of study 1 and by 13% (P<.001) after 2 weeks' treatment, and was not inferior to M8. In terms of anginal attack frequency and nitroderivative consumption, M16 was not inferior to M8 in either study. Moreover, compared with M8, M16 produced a statistically and clinically significant reduction in the incidence of anginal attacks in elderly (>/=75 y) but not in younger patients (<75 y) (study 2), nor in patients from study 1. No significant difference from M8 was found in either study in short-acting nitroderivative consumption. No tolerance to M8 or M16 was observed after 2-week treatment. No statistically significant differences in incidences of all AEs and drug-related AEs were observed between M16 and M8 in either study. The same held true for proportions of patients experiencing AEs and drug-related AEs on M16 vs M8: in study 1-14.3% and 11.8% for all AEs (P=.218), 6.9% and 5.4% for drug-related AEs (P=.280); in study 2-1.3% and 1.3% for all AEs, 0% and 1.3% for drug-related AEs (P>.10) in young patients; and in the elderly, 3.6% and 0% for drug-related AEs (P>.10). Only the proportion of elderly patients with all AEs was significantly higher with M16 than with M8: 14.5% vs 1.8% (P=.039). M16 once daily was effective and well tolerated in investigated patients with stable angina pectoris, particularly the elderly, affording 24 hours of therapeutic activity. M16 was not inferior to M8 given twice daily in terms of efficacy, safety profile, and tolerability.

A pilot double-blind randomized placebo-controlled study of molsidomine 16 mg once-a-day in patients suffering from stable angina pectoris: correlation between efficacy and over time plasma concentrations

OBJECTIVES

A new once-a-day (o.a.d.) formulation of molsidomine (16 mg) was evaluated in patients with stable angina pectoris. The aims were to characterize its pharmacokinetics after a single dose, to demonstrate its clinical efficacy and safety versus placebo and to investigate correlations between pharmacokinetics and pharmacodynamics.

METHODS

Forty-two patients were recruited in a double-blind, crossover, randomized placebo-controlled trial. The pharmacokinetics of molsidomine and SIN-1, its active metabolite, were determined at specific time points (3, 6, 10, 14, 18, 22 and 24 h) after the administration of a single dose of molsidomine 16 mg o.a.d. in all patients distributed into seven groups. Twenty-eight of these 42 patients showed a positive baseline cycloergometric exercise test response during the run-in placebo period and were used to compare the efficacy of molsidomine to placebo. Relationships between plasma concentration in molsidomine or SIN-1 and ischemic threshold were assessed in 16 of the 28 patients with a positive exercise test at baseline. Indeed, the censored variable ischemia-limited tolerance to exercise could not be evaluated in those patients who did not show exercise-induced ischemia anymore under molsidomine 16 mg o.a.d. Pharmacokinetic-pharmacodynamic relationships were evaluated using regression models and correlation coefficients.

RESULTS

The highest average concentration in molsidomine and SIN-1 occurred after 6 h, then a plateau of 15-20 ng/ml molsidomine and 0.8-3.0 ng/ml SIN-1 was maintained for at least 8 h and the mean residual molsidomine concentration 24 h post-drug intake was around 8 ng/ml, still in the effective range of 5-10 ng/ml. A significant increase in total workload (+52 W min, P=0.009), total exercise time (+32 s, P=0.003) and time to angina (+25 s, P=0.016) was measured with molsidomine 16 mg o.a.d. relative to placebo. Using linear regression, significant correlation coefficients were determined between molsidomine plasma concentrations (but not SIN-1) and exercise test improvements (r=0.827, P<0.001 for the total workload; r=0.772, P<0.001 for the total exercise time; and r=0.566, P=0.028 for the time to 1 mm ST-segment depression).

CONCLUSION

The pharmacokinetics of molsidomine 16 mg in patients with stable angina pectoris is compatible with a o.a.d. dosage regimen. This o.a.d. formulation is effective and well-tolerated, providing a 24-h therapeutic control of myocardial ischemia. A positive and significant linear relationship between molsidomine plasma concentration and the increase in exercise tolerance was observed.

Pharmacokinetic strategies in deciphering atypical drug absorption profiles

Drug absorption is a very complex process that manifests itself through potential interaction with a host of physicochemical and physiological variables. Some factors that may affect the absorption processes include presystemic metabolism/efflux, the "absorption window" along the gastrointestinal tract, disease states, demographics (gender, age, ethnicity), and biopharmaceutical classification of solid dosage forms. Despite the complexity of the absorption processes, the analysis of the absorption kinetic data is mostly empirical, and the assumption of first-order absorption is axiomatic. Nevertheless, we often encounter irregular drug absorption profiles (such as double-peak, absorption window-type absorption profiles, etc.) that cannot be satisfactorily described by a simple first-order absorption process. The selection of an inappropriate absorption model would result in the misspecification of the pharmacokinetic model and subsequent erroneous prediction of the dosing regimen. This article presents several pharmacokinetic strategies in analyzing typical and atypical absorption profiles. The atypical absorption profiles discussed in this article include parallel first-order absorption, mixed zero-order and first-order absorption, Weibull-type absorption, absorption window with or without Michaelis-Menton absorption, time-dependent absorption, and inverse Gaussian density absorption. In any event, intravenous drug concentration-time data are generally needed to avoid the ambiguousness in the absorption analyses.

Infusions with molsidomine and isosorbide-5-mononitrate in congestive heart failure: mechanisms underlying attenuation of effects

The use of nitrates for treatment of heart failure is encumbered by tolerance, caused by whatever mechanism, which has been reported only in a few instances with sydnonimines. Accordingly, we compared molsidomine (6 mg/h) and isosorbide-5-mononitrate (3.75 mg/h) with respect to maximal hemodynamic effects, rapidity and extent of attenuation, and underlying mechanisms by means of constant infusions over 24 h each in 15 patients with chronic congestive heart failure (NYHA II-III) with a placebo-controlled, double-blind, randomized, crossover protocol. Hemodynamic measurements and determinations of neurohormones were performed at baseline and at 2, 8, and 24 h after the beginning of infusions. With molsidomine, reductions of diastolic pulmonary artery pressure by 29% (p < 0.001), by 24% (p < 0.01), and by 24% (p < 0.01) versus placebo were found at 2, 8, and 24 h, which amounted to 19% (p < 0.01), 10% (NS), and 14% (NS) with the nitrate. Cardiac output was meaningfully affected only with molsidomine (+5%, NS, at 2 h; +9%, p < 0.05, at 8 h; and +15%, p < 0.05, at 24 h), as was systemic vascular resistance (-13%, p < 0.05; -9%, NS; and -18%, p < 0.01) at the corresponding times. Increases in renin activity amounted to 130% (p < 0.001), 117% (p < 0.001), and 112% (p < 0.001) with molsidomine, and to 14, 16%, and 0 (each NS) with the nitrate at the corresponding times. Hematocrit was reduced by 5% (p < 0.001), 7% (p < 0.001), and 12% (p < 0.01) with molsidomine and by 5% (NS), 5% (p < 0.05), and 5% (NS) with the nitrate. We conclude that neurohumoral counterregulation or fluid shift, which is even more pronounced with molsidomine despite longer-lasting effects, has no essential role in nitrate-tolerance development. With molsidomine, such a role cannot be ruled out, although alternatively, a fluid shift from arterial to the low-pressure arm of circulation during the later course of infusion would be even more likely.