The efficacy of a potassium-sparing combination of chlorthalidone and triamterene in the control of mild and moderate hypertension. I.

Chlorthalidone 25 mg/triamterene 50 mg in once-daily oral doses was as effective in reducing blood pressure as chlorthalidone 25 mg alone. The decrease in serum potassium was statistically significantly less with the combination than for chlorthalidone. There were no notable differences between the treatments in any other measure of laboratory safety or adverse reactions.

The efficacy of a potassium-sparing combination of chlorthalidone and triamterene in the control of mild and moderate hypertension. II.

Chlorthalidone 50 mg/triamterene 50 mg in once-daily oral doses was as effective in reducing blood pressure as chlorthalidone 50 mg alone. The decrease in serum potassium was statistically significantly less with the combination than for chlorthalidone. There were no notable differences between the treatments in any other measure of laboratory safety or adverse reaction.

Chlorthalidone-triamterene: a potassium-sparing diuretic combination for the treatment of oedema.

The efficacy of a once-daily combination of chlorthalidone 50 mg plus triamterene 50 mg or chlorthalidone 100 mg plus triamterene 100 mg was compared to that of chlorthalidone 50 mg or 100 mg. This double-blind study was carried out in eighty-eight patients over a treatment period of 12 weeks. All patients entered the active medication period of 12 weeks after a placebo run-in period of 3 to 7 days, during which pretibial or malleolar pitting oedema averaging 2 to 4 mm developed. All patients started at the lower doses, i.e. forty-one started on chlorthalidone 50 mg plus triamterene 50 mg and forty-seven started on chlorthalidone 50 mg. The protocol provided for doubling the dose (but not for reducing it thereafter) at any time during the 12-week period when control of oedema was deemed inadequate. Eight of the combination therapy patients and sixteen of those on chlorthalidone required the higher doses. By Week 12, 96% of the chlorthalidone plus triamterene patients and 100% of the chlorthalidone patients had shown a reduction of at least 2 mm in depth of pits, and 92% and 72%, respectively, had complete disappearance of oedema. The decreases in pitting oedema were paralleled by mean weight losses of 2.4 kg and 3.1 kg, respectively, for the combination treatment group and the chlorthalidone group. Average serum potassium levels throughout the 12-week treatment period were 3.70 mEq/L for the patients taking the combination compared to 3.41 mEq/L of those taking chlorthalidone.(ABSTRACT TRUNCATED AT 250 WORDS)

Indapamide, a new antihypertensive/diuretic agent, in the treatment of patients with edema.

A multicenter, double-blind, parallel-group study of 219 patients with pitting edema of various causes was undertaken to determine the efficacy and safety of indapamide, administered orally (PO) in a 2.5-, 5-, or 10-mg once-daily dose, as compared with hydrochlorothiazide, administered PO in a 100-mg once-daily dose. Efficacy was evaluated by determining each patient's weight and degree of pitting edema periodically during 12 weeks of active treatment. Lessening of edema was measured by changes in the depth of pitting in the pretibial area, ten to 14 inches below the patella. The depth of pitting was assigned an arbitrary number between 0 and 4, with 0 equivalent to no edema and 4 equivalent to more than 6 mm of pitting edema. After one week of treatment, the mean reduction of pitting edema from baseline, using the 0 to 4 scale, was 1.6 (30%) in both the indapamide (mean of the three groups) and hydrochlorothiazide groups. There were no significant differences among the three dosage levels of indapamide. After 12 weeks of treatment the mean decrease from baseline was 1.8 (34%), indicating a stable reduction of edema. The mean weight loss at one week was 2.5 kg for the three indapamide groups and 2.6 kg for the hydrochlorothiazide group; this loss was maintained for the 12 weeks of the study. The mean decreases in weight and pitting edema were clinically and statistically significant (P less than 0.05) for both medications.

Preliminary report on the effects of tiaramide on the ice cube test in patients with idiopathic cold urticaria.

Three subjects diagnosed as having idiopathic acquired cold urticaria were studied to assess the ability of orally administered tiaramide to inhibit the wheal induced following cold challenge with ice cubes placed in contact with the skin, and to establish the safety of multiple doses of 250 mg, q.i.d., for one week administered after a single oral dose of 500 mg. Two subjects completed the study. One subject was known to be unresponsive to antihistamines for allergy and the second was intolerant of antihistamines due to side effects. A third subject discontinued treatment due to an adverse reaction experienced while on the study medication. The skin of the forearm of each subject was exposed to cold stimuli for 1, 2, 3, 4, and 5 minutes by placing five ice cubes on the ventral surface at one minute intervals, and removing all simultaneously five minutes after contact with the first cube. The challenge sites were observed for ten minutes and the area of the wheal, intensity of edema and the time of contact necessary to induce the skin response were recorded. The results of this provocative test following the single and multiple dosage administration of tiaramide were compared to baseline skin responses. After one week of tiaramide treatment at 250 mg, q.i.d., both subjects who completed the study had a markedly attenuated skin response to cold challenge and no adverse effects. Our results suggest that absorbable compounds that can inhibit mast cell degranulation may be efficacious in cold urticaria and of particular value in treating patients who do not respond to standard therapy.

Inhibition of compound 48/80 induced mediator release following oral administration of tiaramide hydrochloride in normal subjects.

The ability of tiaramide hydrochloride (RHC 2592) to inhibit cutaneous reactivity was studied using 11 normal volunteers. After repeated administration tiaramide hydrochloride inhibited cutaneous mast cell mediator release induced by compound 48/80 while not affecting histamine-induced cutaneous reactivity. This is the first demonstration in man of an oral agent with such an effect.

Long-term experience with indapamide.

Indapamide, 2.5 mg administered once daily for periods up to 36 months, was found to be safe and effective for the long-term control of mild to moderate hypertension. The effects of hydrochlorothiazide, 50 mg, and indapamide, 2.5 mg, were studied in two randomized, double-blind, multicenter trials. Data from the two multicenter trials (20 study sites) were pooled for purposes of comparison. Significant reductions in systolic and diastolic blood pressure, with patients in both supine and standing positions, occurred in both groups within the first 8 weeks of treatment. This effect was maintained throughout the active treatment period. Success, as determined by the therapeutic success rate (percentage of patients with decreases of standing phase V diastolic blood pressure of at least 10 mm Hg or to below 90 mm Hg), occurred in 53% of the patients given hydrochlorothiazide and in 56% of the indapamide-treated patients. During the study period, the nature, frequency, and severity of adverse reactions were similar for both groups. There was no clinically significant difference between the treatment groups for the laboratory assessments. Patients who completed the multicenter trials were eligible for participation in an ongoing long-term extension study of the safety of indapamide. Data are available for periods up to 36 months and demonstrate neither augmentation of clinical or laboratory adverse effects nor any potentially harmful indicators that could be attributed to prolonged treatment.

Pharmacokinetics and clinical pharmacology of indapamide.

Indapamide is a new antihypertensive diuretic agent indicated for the treatment of hypertension and edema. Indapamide shows an alteration in vascular reactivity to calcium and other agonists, suggesting the possibility of a direct vascular effect. The drug is recommended in doses of 2.5 to 5 mg once a day. It is rapidly and completely absorbed from the gastrointestinal tract, resulting in maximal blood levels in approximately 2.3 hours. Coadministration of indapamide with food or antacids does not reduce bioavailability. Linear proportionality of blood concentration with increasing doses is evident following both single and multiple doses. Other pharmacokinetic parameters are not dose related. Indapamide is widely distributed in the body with extensive binding to erythrocytes. Binding to plasma proteins is approximately 76%. Disappearance of indapamide from the blood is biphasic, with a terminal half-life of approximately 16 hours. Renal clearance represents less than 10% of the total systemic clearance of the parent drug, showing the dominant role of hepatic clearance. Studies of 14C-labeled indapamide in humans demonstrate that 70% of the radioactivity is excreted in urine and 23% in feces. Indapamide is extensively metabolized; less than 7% of the dose is excreted in urine as unchanged compound. Studies of patients with renal impairment showed little or no accumulation of indapamide in the blood in comparison to patients with normal renal function. Clinical studies demonstrate that indapamide has diuretic properties. Free water clearance studies indicate a site of action in the cortical diluting segment of the distal tubules. No adverse effect of indapamide on renal function is evident in normal volunteers, hypertensive patients, or geriatric hypertensive patients, as determined by glomerular filtration rate or effective renal plasma flow. Hemodynamic studies of indapamide in patients with mild to moderate hypertension show a significant (p less than 0.05) decrease in mean blood pressure (16%) and total peripheral resistance (15%). No other significant hemodynamic effects are evident. The data suggest that indapamide may produce antihypertensive activity through a dual mechanism of action--diuretic and direct vascular. Additionally, it appears to be safe even for patients with impaired renal function.

Indapamide in the stepped-care treatment of obese hypertensive patients.

A double-blind study was carried out in obese patients with moderately severe hypertension to assess the efficacy and tolerability of 2.5 mg indapamide as a once-a-day Step 1 drug compared to 50 mg hydrochlorothiazide also as a once-a-day Step 1 drug; to assess the efficacy and tolerability of a fixed daily dose of 2.5 mg indapamide administered concomitantly with methyldopa starting at 500 mg daily; and to compare the findings of efficacy and tolerability of 2.5 mg indapamide daily with those of 50 mg hydrochlorothiazide daily as Step 1 agents when methyldopa is the Step 2 drug. Twenty-nine patients completed the study and were evaluated. Nine patients achieved the study criterion of reduction of average standing diastolic pressure to 90 mmHg or less when treated with Step 1 medication only. Twenty patients required the addition of methyldopa to their Step 1 medication: 10 patients took 2.5 mg indapamide with an average constant daily dose of 1100 mg methyldopa and 10 patients took 50 mg hydrochlorothiazide with an average constant daily dose of 1575 mg methyldopa to achieve blood pressure control. All groups had mean diastolic pressure controlled at or below the 90 mmHg criterion during the period of constant methyldopa dosage for those patients who required Step 2 therapy. There were no significant differences between groups with respect to diastolic pressure during the constant dosage period. The indapamide patients required significantly (p less than 0.05) less methyldopa than did the hydrochlorothiazide patients in order to maintain satisfactory control of diastolic blood pressure. The number of responders was greater in the 2.5 mg indapamide + methyldopa group than it was in the 50 mg hydrochlorothiazide + methyldopa group, and responses were achieved more rapidly in the former group than in the latter. Indapamide (2.5 mg per day) was effective and well tolerated when used alone or as Step 1 medication in combination with methyldopa as Step 2 medication, and it compared favourably in this regard with hydrochlorothiazide.

Multicenter dose-response study of the effect of indapamide in the treatment of patients with mild to moderate hypertension.

This study, carried out in three centers in the United States, investigated the antihypertensive effect of three dosages of indapamide in 87 patients with mild to moderate hypertension. The dosages studied were 1 mg, 2.5 mg, and 5 mg daily. A double-blind, parallel study design was used with a six-week placebo run-in period followed by an eight-week treatment period and a two-week follow-up period. Compared with placebo, all dosages caused a significant decrease (P less than 0.05) in blood pressure, with an average decrease of approximately 6 mmHg diastolic and 13 mmHg systolic. The antihypertensive effect seemed to be fully manifest after six weeks of treatment. At all dosage levels, indapamide produced markedly greater therapeutic success rates than did the placebo. Success was defined as either a standing phase-5 diastolic blood pressure of less than 90 mmHg or a decrease by at least 10 mmHg from baseline. Although the decrease in mean serum potassium concentration was dose-related, the decrease was not clinically significant with any dose. A reduction in serum chloride and increases in serum uric acid and glucose were also observed. These changes were slight and did not cause the discontinuation of treatment for any patient. The most frequently observed side effects were mild to moderately severe dizziness, weakness, and headaches.

Multi-centre clinical investigation of indapamide in the United States: a review.

Indapamide, a new indoline antihypertensive agent, has been the subject of a worldwide programme to develop this drug for general clinical use. The results are described of the multi-centre U.S. clinical programme demonstrating the effectiveness and tolerance of indapamide for the treatment of hypertension. All work was conducted under U.S. Federal Food and Drug Administration guidelines, and resulted recently in a New Drug Application. A total of 1891 subjects or patients participated in 27 separate studies conducted by 91 investigators. In controlled clinical trials comparing 2.5 mg indapamide once daily with 50 mg hydrochlorothiazide once daily for 40 weeks in patients with mild to moderate essential hypertension, indapamide produced a reduction of supine blood pressure of -9.5/-14.3 mmHg as compared with -7.6/-11.4 mmHg for hydrochlorothiazide. In combination with methyldopa, propranolol, clonidine, guanethidine and hydralazine, indapamide consistently produced a greater decrease in arterial pressure than did those agents given alone. Indapamide added to these step-care agents did not result in a meaningful increase in adverse reactions. Indapamide has been the subject of a long-term safety study in which over 100 hypertensive patients have been followed up for 2 years or longer. During this period of time, indapamide was well tolerated and remained effective. No biochemical, electrocardiographic or ophthalmological changes were associated with its use. Other studies with indapamide are discussed describing the systemic and renal haemodynamic effects, pharmacokinetic properties and special safety studies conducted with this agent. The use of indapamide in patients with hepatic or renal impairment is reviewed in detail.

Pharmacokinetics and bioavailability of indapamide--a new antihypertensive drug.

Two formulations of indapamide tablets (2.5 mg) were given as a 5.0 mg dose and the subsequent blood levels were compared to those obtained after administration of a 5.0 mg solution. The study was conducted as a randomized three-way crossover design using healthy male volunteers. The drug was well tolerated by all the subjects involved. The area under the blood concentration versus time curve, extrapolated to infinity was essentially the same for all three formulations (4.2, 4.7, and 4.4 microgram-h/ml). Statistical comparison of the blood levels from the two tablets showed that one tablet had a significantly shorter time of maximum blood concentration (2.3 vs 3.5). Cmax(333ng/ml) and tmax (0.7h) values for the solution were significantly higher than either tablet. The average half-life (beta-phase) for all three formulations was 15 h, while the average systemic clearance was 20 ml/min. Indapamide has a low clearance rate and there was no evidence that the drug undergoes a first-pass effect.

RHC 3659: a new orally active angiotensin converting enzyme inhibitor in normal volunteers.

1 The new converting enzyme inhibitor RHC 3659 was tested in 15 male volunteers. The study consisted of two parts: first, the ability of a single oral dose (5, 10, 20, 40 or 80 mg) to inhibit the pressor response to exogenous angiotensin I was tested with blood pressure and heart rate monitored continuously through an intraarterial catheter. A dose-related shift to the right of the pressor response curve to angiotensin I was observed with a peak occurring within 0.5 to 1 h. The pressor response to angiotensin II was unaffected. 2 In the second part, plasma renin and converting enzyme activity, angiotensin II and aldosterone were measured serially before and up to 8 h after administration of a single oral dose of RHC 3659. As expected. plasma angiotensin II and aldosterone fell within 30 min while plasma renin activity increased. Plasma converting enzyme activity was suppressed at 0.5 h in a dose-related manner with levels still below 30% of control 4 h following 80 mg of the inhibitor. 3 However, in vitro the enzyme-inhibitor complex seemed quited fragile since during storage of the plasma samples at -20 degrees C, converting enzyme activity increased significantly already within days (P less than 0.001, n = 28) and continued to rise for more than 2 months. This fragility may explain the seemingly lower potency of RHC 3659 when compared to captopril. No side effects were observed.

Disposition of captopril in normal subjects.

The disposition of captopril, an angiotensin-converting enzyme inhibitor with antihypertensive properties, was studied in 10 normal male subjects after a single 100-mg tablet of 35S-labeled drug. Average absorption parameters for unchanged captopril in blood were Tmax 0.93 +/- 0.08 hr and Cmax 800 +/- 76 ng/ml. For total radioactivity in blood the values were Tmax 1.05 +/- 0.08 hr and Cmax 1,580 +/- 90 ng/ml (as captopril equivalents). Because of the curvilinearity of the semilogarithmic plots of blood concentrations of captopril:time, elimination half-life (t1/2) of unchanged drug could not be determined. At 1 hr unchanged captopril accounted for about 52% of total radioactivity in blood, and the dimeric disulfide metabolite of captopril accounted for about 10%. In the first 5 days after dosing, an average of about 68% of the radioactive dose was recovered in urine and 18% in feces. The distribution of radioactivity in the first 24-hr urine sample (66% of the dose) was 58% captopril (38% of dose), 2% captopril disulfide (1.5% of dose), and 40% unidentified polar metabolites (26% of dose).

Effects of nadolol beta-blockade on blood pressure in hypertension.

Nadolol, a nonselective beta adrenoceptor antagonist, was evaluated in 9 normal sybjects with essential hypertension for ability to inhibit exercise-induced changes in double-product (systolic pressure x heart rate). Propranolol and placebo were included as positive and negative controls. The beta antagonists were administered orally in single doses at 10, 20, 40, and 80 mg on a crossover basis. Both nadolol and propranolol induced comparable dose-related inhibition of double-product. Duration of beta receptor blockade was greater with nadolol than with propranolol; significant inhibition of double-product occurred 24 hr after a single 80-mg dose of nadolol. The antihypertensive effect of nadolol was evaluated in another series of 46 subjects with essential hypertension. The dose of nadolol ranged from 80 to 320 mg once daily. Consistent decreases in supine heart rate (20%) and diastolic blood pressure (9%) from baseline were observed. During steady state, the oral daily dose of nadolol was proportional to the minimum steady-state serum concentration (Cmin) of nadolol (r = 0.75, p less than 0.001) obtained just before the next dose of nadolol. Statistically significant correlation was observed between the antihypertensive effect and the Cmin for nadolol (r = 0.45, p less than 0.05).

Effect of beta-blockers on exercise double product (systolic blood pressure x heart rate).

1 The effect of single oral doses of six beta-receptor antagonists on exercise-induced changes in double product (systolic blood pressure x heart rate) were studied in 25 human volunteers. 2 Three doses of propranolol, nadolol, oxprenolol, pindolol, timolol and atenolol were selected for study on the basis of in vivo beta-blocking potency. 3 Although all beta-blockers studied reduced the double product response to exercise, the pharmacodynamics of this effect differed markedly. 4 Pharmacodynamic half-lives, estimated for the drug tested, were 39 h for nadolol, atenolol 21 h, timolol 15 h, oxprenolol 13 h, propranolol 11 and pindolol 8 h. 5 These results suggest that the clinical choice of a beta-blocker with the least problems of compliance can be made on the basis of pharmacodynamics as well as pharmacological profile.

Elimination of nadolol by patients with renal impairment.

1 Nadolol excretion was studied in 24 patients with chronic renal failure. 2 The amount of nadolol excreted during the 120-h period after receiving the drug ranged from less than 1% in functionally anephric, patients up to 11.5% in patients with average creatinine clearance of 57.9 +/- 3.6 ml/min/1.73 m2. 3 Renal clearance of nadolol was found to correlate with creatinine clearance; nadolol elimination is retarded in patients with renal failure. 4 Nadolol serum half-life is prolonged in proportion to the remaining renal function. Therefore, dosage intervals in renal patients receiving nadolol should be adjusted to creatinine clearance. 5 Haemodialysis effectively reduced serum concentration of the drug; it may therefore be a useful therapy for drug intoxication.