A double-blind multiple crossover trial evaluating a transdermal nitroglycerin system vs placebo

Fifty-six patients with angina pectoris on effort participated in a 28-day study comparing a transdermal nitroglycerin system (TNS) against placebo. The protocol was based on a regular double-blind multi-crossover pattern. The variables recorded included daily sublingual nitroglycerin requirement, daily anginal attack frequency, and a subjective patient evaluation of each day on a visual analog scale. TNS dosage ranged from 10 cm2 (5 mg per 24 h) to 60 cm2 (30 mg per 24 h) based on the patient's dosage prior to commencement of the study. All other medication was continued unchanged. The results demonstrate improvement on active therapy in the patient group using greater than or equal to 20 cm2 TNS whereas no significant improvement in patients using 10 cm2 TNS was seen. In the higher dose group, the mean number of daily anginal attacks was 2.5 on placebo and 1.4 on active therapy (P less than 0.0001). Corresponding mean daily sublingual nitroglycerin requirement was 3.6 on placebo and 2.3 on active therapy (P less than 0.0001). Although TNS therapy was associated with significant improvement in the group using the higher dosage, the results suggest the development of tolerance on active therapy. The possibility of rebound effect and the absence of demonstrable efficacy in the low dose group require further investigation.

Acute and chronic hemodynamic effects of enalapril (MK-421) in congestive heart failure

Enalapril, a new long-acting angiotensin-converting enzyme inhibitor, was administered orally to 12 patients with stable congestive cardiac failure, NYHA function class III-IV. Acute and chronic hemodynamic effects were evaluated in addition to clinical response. The results of this open pilot study indicated marked reduction of pulmonary capillary wedge pressure from 21.8 +/- 5.9 mm Hg (mean +/- 1 SD) to 13.3 +/- 4.5 mm Hg (P less than 0.01) and peripheral resistance from 1837 +/- 860 dynes X sec-1 X cm-5 to 1063 +/- 584 dynes X sec-1 X cm-5 at 6 hr (P less than 0.01). Well-tolerated hypotension with mean arterial pressure from 88.0 +/- 11.6 mm Hg to 73.1 +/- 11.7 mm Hg at 6 hr (P less than 0.01) was recorded. No significant increase in cardiac output was observed. Angiotensin-converting enzyme activity was powerfully inhibited at the time of peak hemodynamic effect from 25.3 +/- 9.8 U/ml to 4.9 +/- 3.4 U/ml (P less than 0.01) and sustained, but attenuated reduction at 24 hr (8.7 +/- 4.7 U/ml) was observed. All patients reported subjective improvement and this clinical improvement has been sustained during follow-up from 19 to 21 months although baseline hemodynamic parameters at chronic re-catheterization did not demonstrate significant improvement. The pharmacodynamics and toxicity of enalapril as compared to captopril are discussed. The long half-life, low toxicity and gradual onset of action are seen as representing a clinical advantage with regard to patient therapy.

Acute and long-term response to enalapril in congestive failure

Enalapril, a novel long acting angiotensin converting enzyme (ACE) inhibitor, was given orally to 12 patients with chronic heart failure (NYHA functional class III and IV) and cardiomegaly. The optimal dose averaged 17 mg given once-daily. Heart rate, systemic arterial blood pressure, pulmonary arterial pressure, right and left ventricular filling pressures and cardiac index were monitored during dose efficacy titration. Eleven patients were recatheterised 3 months later. After stabilisation of cardiac filling pressures, all patients had left ventricular filling pressures in excess of 20 mmHg. Enalapril increased cardiac index acutely by 34% but at 12 weeks follow-up, cardiac index was not different from control levels. Left ventricular filling pressure was reduced acutely by 36% and by 41% at 3 months. Heart rate, systemic arterial and right atrial pressures and plasma concentrations of aldosterone were reduced during the observation period. ACE activity was inhibited at the time of peak haemodynamic effect from 25.3 +/- 9.8 to 4.9 +/- 3.4 U/ml (P less than 0.01). Renin was markedly elevated. These changes were accompanied by marked and sustained clinical improvement and subjective well-being.

Sustained haemodynamic effects of enalapril in left ventricular failure

Enalapril, a novel angiotensin converting enzyme inhibitor, was given orally to 12 patients with chronic heart failure (NYHA functional class III and VI) and cardiomegaly. Heart rate, systemic arterial blood pressure, pulmonary arterial pressure, right and left ventricular filling pressures and cardiac index were monitored during dose efficacy titration. The optimal dose averaged 17 mg given once-daily. All patients were recatheterized three months later. After stabilization of cardiac filling pressures, all patients had left ventricular filling pressures in excess of 18 mmHg. Enalapril increased cardiac index acutely by 34% but at 12 weeks follow-up, cardiac index was not different from control levels. Left ventricular filling pressure was reduced acutely by 36% and by 41% at three months. Heart rate, systemic arterial and right atrial pressures and plasma concentrations of aldosterone were reduced during the observation period. Renin was markedly elevated. These changes were accompanied by marked and sustained clinical improvement and subjective well-being.

Successful management of severe congestive cardiac failure with enalapril

The new angiotensin-converting enzyme inhibitor enalapril (MK-421) was administered to a patient with severe congestive cardiac failure. Dramatic and sustained symptomatic and hemodynamic improvement is reported. The possible clinical significance of this agent's favorable profile is briefly discussed.