Placebo-controlled, double-blind clinical trial of alprenolol in African hypertensive patients

Systematic review: antihypertensive drug therapy in patients of African and South Asian ethnicity

Despite the large differences in the epidemiology of hypertension across Europe, treatment strategies are similar for national populations of white European descent. However, hypertensive patients of African or South Asian ethnicity may require ethnic-specific approaches, as these population subgroups tend to have higher blood pressure at an earlier age that is more difficult to control, a higher occurrence of diabetes, and more target organ damage with earlier cardiovascular mortality. Therefore, we systematically reviewed the evidence on antihypertensive drug treatment in South Asian and African ethnicity patients. We used the Cochrane systematic review methodology to retrieve trials in electronic databases including CENTRAL, PubMed, and Embase from their inception through November 2015; and with handsearch. We retrieved 4596 reports that yielded 35 trials with 7 classes of antihypertensive drugs in 25,540 African ethnicity patients. Aside from the well-known blood pressure efficacy of calcium channel blockers and diuretics, with lesser effect of ACE inhibitors and beta-blockers, nebivolol was not more effective than placebo in reducing systolic blood pressure levels. Trials with morbidity and mortality outcomes indicated that lisinopril and losartan-based therapy were associated with a greater incidence of stroke and sudden death. Furthermore, 1581 reports yielded 16 randomized controlled trials with blood pressure outcomes in 1719 South Asian hypertensive patients. In contrast with the studies in African ethnicity patients, there were no significant differences in blood pressure lowering efficacy between drugs, and no trials available with mortality outcomes. In conclusion, in patients of African ethnicity, treatment initiated with ACE inhibitor or angiotensin II receptor blocker monotherapy was associated with adverse cardiovascular outcomes. We found no evidence of different efficacy of antihypertensive drugs in South Asians, but there is a need for trials with morbidity and mortality outcomes. Screening for cardiovascular risk at a younger age, treating hypertension at lower thresholds, and new delivery models to find, treat and follow hypertensives in the community may help reduce the excess cardiovascular mortality in these high-risk groups.

Blood pressure lowering efficacy of partial agonist beta blocker monotherapy for primary hypertension

BACKGROUND

Partial agonists are a subclass of beta blockers used to treat hypertension in many countries. Partial agonist act by stimulating beta receptors when they are quiescent and blocking beta receptors when they are active. The blood pressure (BP) lowering effect of partial agonist beta blockers has not been quantified.

OBJECTIVES

To quantify the dose-related effects of various partial agonists beta blockers on systolic blood pressure (SBP), diastolic blood pressure (DBP) and heart rate versus placebo in patients with primary hypertension.

SEARCH METHODS

We searched the Hypertension Group Specialised Register, the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, MEDLINE In-Process, EMBASE and ClinicalTrials.gov for randomized controlled trials up to October 2014. The WHO International Clinical Trials Registry Platform (ICTRP) is searched for inclusion in the Group's Specialised Register.

SELECTION CRITERIA

Randomized double-blinded placebo-controlled parallel or cross-over trials. Studies must contain a partial agonist monotherapy arm with fixed dose. Patients enrolled into the studies must have primary hypertension at baseline (defined as SBP/DBP > 140/90 mmHg). Duration of studies must be between three to 12 weeks.

DATA COLLECTION AND ANALYSIS

Two authors (GW and HB) confirmed the inclusion of studies and extracted the data independently.

MAIN RESULTS

Thirteen randomized double-blinded placebo-controlled trials that examined the blood pressure lowering efficacy of six partial agonists in 605 hypertensive patients were included in this review. Five of the included studies were parallel studies and the other eight were cross-over studies. The overall risk of bias is high in this review due to the small sample size and high risk of detection bias. Pindolol, celiprolol and alprenolol lowered SBP and DBP compared to placebo. Acebutolol lowered SBP but there was no clear evidence that it lowered DBP. There was no clear evidence that pindolol and oxprenolol lowered SBP or DBP. Other than for celiprolol, sample sizes were generally small increasing the uncertainty in findings for individual agents versus placebo. In patients with moderate to severe hypertension, partial agonists (considered as a subclass) lowered peak BP by an average of 8 mmHg systolic (95% CI, -10 to -6, very low quality evidence), 4 mmHg diastolic (95%CI, -5 to -3, very low quality evidence) and reduced heart rate by five beats per minute (95%CI, -6 to -4, very low quality evidence). Higher dose partial agonists did not appear to provide additional BP lowering effects compared to lower dose. The maximum BP lowering effect of the overall subclass occurred at the starting dose. Partial agonists reduced pulse pressure by 4 mmHg (95% CI, -5 to -2, very low evidence). Only one study reported withdrawal due to adverse effects, the risk ratio (95% confidence interval) was 0.72 (0.07, 7.67).

AUTHORS' CONCLUSIONS

There was very low quality evidence that in patients with moderate to severe hypertension, partial agonists lowered peak BP by an average of 8/4 mmHg and reduced heart rate by five beats per minute. There was no evidence of a greater effect at doses higher than the initial doses. This estimate was probably exaggerated as it was subject to a high risk of bias. Based on the indirect comparison of the results in this review and two Cochrane reviews on angiotensin-converting-enzyme (ACE) inhibitors and angiotensin receptor blockers (ARBs), which also used similar inclusion criteria as this review, the BP lowering effect appeared to be less than the effect in patients with mild to moderate elevated BP who were taking ACE inhibitors and ARBs based on an indirect comparison. Withdrawals due to adverse effects were only reported in one trial so it is impossible to assess the harm of these drugs.

Blood pressure, prevalence of hypertension and hypertension related complications in Nigerian Africans: A review

To review studies on hypertension in Nigeria over the past five decades in terms of prevalence, awareness and treatment and complications. Following our search on Pubmed, African Journals Online and the World Health Organization Global cardiovascular infobase, 1060 related references were identified out of which 43 were found to be relevant for this review. The overall prevalence of hypertension in Nigeria ranges from 8%-46.4% depending on the study target population, type of measurement and cut-off value used for defining hypertension. The prevalence is similar in men and women (7.9%-50.2% vs 3.5%-68.8%, respectively) and in the urban (8.1%-42.0%) and rural setting (13.5%-46.4%).The pooled prevalence increased from 8.6% from the only study during the period from 1970-1979 to 22.5% (2000-2011). Awareness, treatment and control of hypertension were generally low with attendant high burden of hypertension related complications. In order to improve outcomes of cardiovascular disease in Africans, public health education to improve awareness of hypertension is required. Further epidemiological studies on hypertension are required to adequately understand and characterize the impact of hypertension in society.

WITHDRAWN: Effect of antihypertensive drugs on mortality, morbidity and blood pressure in blacks

BACKGROUND

Black people have a greater prevalence of elevated blood pressure leading to excess morbidity and mortality.

OBJECTIVES

To systematically review the effects of different antihypertensive drugs on mortality, morbidity and blood pressure black adults with elevated blood pressure.

SEARCH STRATEGY

Medline, Embase, LILACS, African Index Medicus, the Cochrane Library November 2003; Pubmed September 2003 to March 2004. Searches were conducted without language restriction.

SELECTION CRITERIA

Randomised controlled trials of drugs versus placebo (blood pressure outcomes) or versus placebo or other drugs (morbidity and mortality outcomes).

DATA COLLECTION AND ANALYSIS

Two reviewers independently extracted data unblinded. Disagreements were resolved by discussion. Authors were contacted twice to obtain missing information.

MAIN RESULTS

Full reports or abstracts from more than 2900 references of papers yielded 30 trials considering 53 interventions with 8 classes of antihypertensive drugs in 20,006 black patients from Africa, the Caribbean, and the United States of America, aged 18 to >80 years. In one large trial the main morbidity and mortality outcomes did not differ significantly between initial treatment drug classes when drugs were added to reach goal blood pressures. However, the comparison ACE Inhibitors vs diuretic favoured the diuretic for stroke 1.40 [1.17 to 1.68]; combined CHD 1.15 [1.02 to 1.30] and combined CVD 1.19 [1.09 to 1.30] and the comparison alpha blocker vs diuretic favoured the diuretic for combined CVD 1.40 [1.25 to 1.57]. In addition, all comparisons for heart failure favoured diuretic (1.47 [1.24 to 1.74] vs calcium blocker; 1.32 [1.11 to 1.58] vs ACE Inhibitor; and 2.18 [1.73 to 2.74] vs alpha blocker. The results also showed a greater occurrence of diabetes with diuretics. No significant differences were detected between placebo and beta adrenergic blockers in the reduction of systolic blood pressure (weighted mean difference [95% CI], -3.52 [-7.50 to 0.46] mm Hg). In addition, ACE inhibitors did not significantly differ from placebo in achievement of goal diastolic blood pressure (risk difference [95% CI], 5% [-10% to 21%]). Calcium blockers, diuretics, centrally acting agents, alpha adrenergic blockers and angiotensin II antagonists were all more effective than placebo in reducing blood pressure in the pooled analyses. Only calcium blockers remained effective in all prespecified subgroups, including baseline diastolic blood pressure >109 mm Hg.

AUTHORS' CONCLUSIONS

When first-line drugs from different classes are compared in the treatment of black people, there is no evidence of differential effects on most mortality and morbidity outcomes. Those morbidity differences that were found favoured diuretics. Drugs differ in their ability to reduce blood pressure in black people. Calcium blockers were the only drug class that reduced blood pressure in all subgroups of black people including those with severe hypertension. Beta-blockers, angiotensin receptor blocker, alpha blockers and ACE Inhibitors were least good at reducing blood pressure in black adults.

The lack of efficacy of topical beta-blockers, timolol and betaxolol on intraocular pressure in Nigerian healthy volunteers

PURPOSE

The beta-adrenoceptor antagonists are commonly used drugs in ophthalmic and medical practice. While beta-blockers may show reduced antihypertensive efficacy in African patients, the effect of beta-blockers on intraocular pressure (IOP) in African healthy volunteers is less well known.

METHODS

This single-masked, placebo-controlled, randomised study was conducted to investigate the response of healthy Nigerian volunteers to a single drop of the beta-adrenoceptor antagonists timolol and betaxolol. Twenty-five volunteers participated in the study; however, only 19 were able to complete the study. The concentrations of the beta-blocker used were 0.0625%, 0.125%, 0.25% and 0.5%. One eye of the volunteers was used while the other eye served as control. The baseline IOP was documented and IOP measured hourly over 6 h. Pupillary size, corneal sensitivity and visual acuity were also assessed. Cardiovascular parameters were also documented hourly (blood pressure, heart rate, pulse rate).

RESULTS

Only 0.5% concentrations of both beta-adrenoceptor antagonists caused any significant IOP reduction in normal volunteers (p < 0.05). The maximal falls were -2.33 +/- 2.2 mmHg and -1.23 +/- 0.6 mmHg with timolol and betaxolol, respectively. The IOP reduction produced lasted for only 4 h, after which the IOP returned to baseline. There was also an overshoot of the IOP above the baseline values in all the volunteers (+2.0 to +2.3 mmHg). There was no significant change in the cardiovascular parameters. There was no effect on the pupillary size, visual acuity or corneal sensitivity. There was no significant change in IOP and cardiovascular parameters in the placebo group.

CONCLUSIONS

Both beta-adrenoceptor antagonists caused an attenuated IOP reduction in African normal volunteers, compared with values reported in Caucasians. There was a rebound intraocular hypertensive effect demonstrated with both beta-adrenergic antagonists in blacks.

Racial differences in drug responses--a comparative study of trimazosin and alpha 1-adrenoceptor responses in normotensive Caucasians and West Africans

The possible racial differences in alpha 1-adrenoceptor responsiveness and the blood pressure and heart rate responses following alpha 1-adrenoceptor antagonism with trimazosin have been investigated in matched groups of six Caucasians and six Nigerians. There were no significant differences between the racial groups in the blood pressure and heart rate responses to oral (200 mg) and intravenous (100 mg) trimazosin. alpha 1-adrenoceptor responsiveness was similar in both groups after placebo and following both active treatments. There were only minor pharmacokinetic differences with the Caucasians having a larger volume of distribution, and a longer terminal elimination half-life for the metabolite, 1-hydroxy-trimazosin. These results suggest a similarity in peripheral vascular alpha 1-adrenoceptor mechanisms and show no major significant racial differences in the pharmacokinetics and pharmacodynamics of trimazosin.

The relative importance of genetic and environmental factors in hypertension in black subjects

Essential hypertension is the most important cardiovascular disease in black subjects. The types of presentation, the pattern of organ involvement and the subsequent complications are similar in black races. The response (or lack of response) to different types of treatment are also alike in blacks when compared with caucasians. Striking racial differences are observed in the plasma and intracellular electrolytes, cation transmembrane transport, salt taste threshold, plasma renin activity and urinary kallikrein activity. The similarities within the black racial groups are very likely to be genetic, although the pattern of inheritance remains controversial. Differences, however, occur in the prevalence and severity of the disease among the black racial groups. That these differences are due partly to environmental causes can not be disputed because even within the same ethnic groups changing patterns are observed in the prevalence of hypertension, in the course of urbanization of rural communities, or on moving from a previously rural to an urban environment. Consequently, genetic factors may be the only important considerations in the severity of hypertension in black subjects.