Optimization of antihypertensive therapy with a novel, extended-release formulation of diltiazem: results of a practice-based clinical study

Pharmacokinetics of a Novel Diltiazem HCl Extended-Release Tablet Formulation for Evening Administration

A novel diltiazem HCl extended-release (ER) tablet formulation was developed for evening administration in the management of angina and hypertension. Pharmacokinetics of the formulation were evaluated to identify variations in morning (7 a.m. or 8 a.m.) versus evening (10 p.m.) drug administration. Single-dose (360 mg) and multiple-dose (360 mg once daily for 7 days), open-label, randomized, two-way crossover studies of the new diltiazem HCl ER tablets were completed in 48 healthy volunteers. Serial plasma samples were collected via direct venipuncture up to 48 hours postdose and analyzed for diltiazem and its two major metabolites by high-performance liquid chromatography (HPLC). The primary parameters used to assess the data were AUC0- infinity, AUC0-tau, AUC6 a.m.-12 p.m., Cmax, and tmax. Statistical comparisons using ANOVA were evaluated after logarithmic transformation of dose-dependent parameters. Diltiazem HCl ER tablets administered in the evening exhibited 17% and 22% greater bioavailability compared to morning administration under single-dose and steady-state conditions, respectively. The two times of drug administration were bioinequivalent in both studies. The evening schedule also provided more than twofold higher plasma diltiazem levels in the critical morning hours, when both blood pressure and the incidence of cardiovascular events are the highest.

IMPPACT: Investigation of Medical Professionals and Patients Achieving Control Together

OBJECTIVE

To determine whether home blood pressure monitoring (HBPM) led to physician-initiated medication titration and improved achievement of target BP levels compared with standard, office-based management.

METHODS

Physicians were randomly assigned to a treatment group or a control group. Patients in the control group were monitored by their physician and were drug-adjusted according to the usual approach. In the treatment group, patients were given home BP monitors (UA-767P [A&D Medical/Lifesource, USA]), and drug dosing was adjusted according to HBPM readings and protocol. Long-acting diltiazem (240 mg/day) was added at baseline, which was adjusted as necessary (other medications were added if more than 360 mg/day of diltiazem was required). A final BP measurement was taken in the office after six weeks.

RESULTS

Nineteen physicians were randomly assigned to the office BP monitoring group and 34 were assigned to the HBPM group. Of the 270 subjects recruited, 97 were in the office BP monitoring group and 173 were in the HBPM group. From baseline to the final visit, there was a statistically significant time by group interaction with lower BP in the HBPM group (P=0.034 for both systolic BP and diastolic BP). BP fell from 159/91+/-11/10 mmHg at baseline in the HBPM group to 138/80+/-13/8 mmHg on the final visit, and from 160/88+/-14/10 mmHg to 141/78+/-10/9 mmHg in the control group.

CONCLUSIONS

BP was lowered significantly in both groups, and to a statistically greater degree in the HBPM group. The Hawthorne effect might have led to altered care by the physicians with improvement in BP control in both groups.

Antihypertensive safety and efficacy and physician and patient satisfaction: results from a phase 4 practice-based clinical experience trial with diltiazem LA

This study was undertaken to assess the safety and efficacy of a new long-acting formulation of diltiazem (DLA) (Cardizem LA; Biovail Pharmaceuticals, Inc., Bridgewater, NJ) in a large heterogeneous group of hypertensive patients, and to evaluate physician and patient treatment satisfaction. In this open-label, 30-day study, physicians enrolled patients with hypertension who were to be evaluated and treated at an initial visit and at 2 follow-up visits. Data recorded for each patient included demographic information, DLA dosing strength, blood pressure (BP) readings, and adverse events (AEs). A total of 15,155 physicians completed the baseline questionnaire, and 9679 (64%) completed the final clinical evaluation questionnaire. In all, 139,965 patients with hypertension were enrolled. Initial and follow-up BP data were recorded for 50,856 (36%) of these patients. On average, systolic BP (SBP) decreased from the initial visit by 10.9 mm Hg at the first follow-up (P<.0001) and by 15.5 mm Hg at the second follow-up (mean SBP, 135.7) (P<.0001). On average, diastolic BP (DBP) decreased by 6.7 mm Hg (P<.0001) and by 9.2 mm Hg (mean DBP, 79.4) (P<.0001), respectively. The most commonly reported AEs included edema, headache, dizziness, nausea, and rash; two thirds of these events were attributed to DLA. None of the AEs attributed to DLA was reported in more than 1% of patients. Both physicians and patients expressed a high degree of satisfaction with DLA. Results from this large-scale, open-label study show that DLA was safe and produced clinically meaningful reductions in SBP and DBP; in addition, a moderate to high degree of physician and patient satisfaction was reported in a large and heterogeneous cohort of patients with hypertension.

Anomalies in the dosing of diltiazem

From early research, investigators understood that the dose of diltiazem required for the treatment of hypertension (commonly 360 mg/day) was greater than that required for the treatment of angina (commonly 240 mg/day). Nonetheless, studies of recent prescribing practices show that the 240 and 180 mg capsule strengths constitute more than 70% of the diltiazem prescriptions for hypertension. Physicians became accustomed to the lower antianginal doses of diltiazem for 7 years before a hypertension indication was approved. Subsequently, these dosing levels were reinforced by the production of once-a-day formulations with highest capsule strengths of 240 mg and 300 mg. These strengths were dictated by the sheer bulk of the formulations, which limited how much diltiazem could be inserted into the #00 capsule, the largest capsule that can be comfortably administered. An examination of the combined data from the six randomized, blinded, and placebo-controlled trials submitted to the FDA for the original new drug applications of the three formulations of diltiazem available in the United States shows a clear linear dose-response relationship between diltiazem dose and blood pressure lowering through the 480-540 mg/day range. It also demonstrates that the 90-120 mg/day range is the "no-effect dose." These conclusions are supported by a MEDLINE review of all other studies of multilevel dosing of higher dose levels of diltiazem. The data support the conclusion that diltiazem is generally underdosed, but when properly dosed may be the single most potent antihypertensive overall.