Pharmacodynamic effects and clinical use of alpha methyldopa in the treatment of essential hypertension

Risk analysis of suicidal ideations and postpartum depression with antenatal alpha methyldopa use

Out of the various risk factors for postpartum depression, use of pharmacotherapy during pregnancy is the most poorly understood. The present study aimed to establish risk of postpartum depression and suicidal ideations with antenatal use of alpha methyldopa. Out of the 100 postpartum women assessed, 77.78% of the women who were prescribed alpha methyldopa had significant postpartum depression. There was statistically significant risk of postpartum depression associated with alpha methyldopa (p = 0.026, OR = 6.45). There was no increased suicidal risk with use of alpha methyldopa in these women (p = 1.00).

Methyldopa for primary hypertension

BACKGROUND

Hypertension is associated with an increased risk of stroke, myocardial infarction and congestive heart failure. Methyldopa is a centrally acting antihypertensive agent, which was commonly used in the 1970's and 80's for blood pressure control. Its use at present has largely been replaced by antihypertensive drug classes with less side effects, but it is still used in developing countries due to its low cost. A review of its relative effectiveness compared to placebo on surrogate and clinical outcomes is justified.

OBJECTIVES

To quantify the effect of methyldopa compared to placebo in randomized controlled trials (RCTs) on all cause mortality, cardiovascular mortality, serious adverse events, myocardial infarctions, strokes, withdrawals due to adverse effects and blood pressure in patients with primary hypertension.

SEARCH STRATEGY

We searched the following databases: Cochrane Central Register of Controlled Trials (1960-June 2009), MEDLINE (2005-June 2009), and EMBASE (2007-June 2009). Bibliographic citations from retrieved studies were also reviewed. No language restrictions were applied.

SELECTION CRITERIA

We selected RCTs studying patients with primary hypertension. We excluded studies of patients with secondary hypertension or gestational hypertension.

DATA COLLECTION AND ANALYSIS

Two reviewers independently extracted data and assessed trial quality using the risk of bias tool. Data synthesis and analysis was performed using RevMan 5. Data for blood pressure were combined using the generic inverse variance method.

MAIN RESULTS

Twelve trials (N=595) met the inclusion criteria for this review. None of these studies evaluated the effects of methyldopa compared to placebo on mortality and morbidity outcomes. Data for withdrawals due to adverse effects were not reported in a way that permitted meaningful meta-analysis. Data from six of the twelve trials (N=231) were combined to evaluate the blood pressure lowering effects of methyldopa compared to placebo. This meta-analysis shows that methyldopa at doses ranging from 500-2250 mg daily lowers systolic and diastolic blood pressure by a mean of 13 (95%CI 6-20) / 8 (95% CI 4-13) mmHg. Overall, the risk of bias was considered moderate.

AUTHORS' CONCLUSIONS

Methyldopa lowers blood pressure to varying degrees compared to placebo for patients with primary hypertension. Its effect on clinical outcomes, however, remains uncertain.

SOME OBSERVATIONS ON THE PHARMACOLOGY OF ALPHA-METHYLDOPA

alpha-Methyldopa in high concentrations impaired the responses of rabbit isolated ileum and guinea-pig isolated vas deferens to stimulation of the sympathetic nerves and to noradrenaline, but these preparations taken from animals previously treated with alpha-methyldopa showed no sign of impairment. Contractions of the cat nictitating membrane were reduced but not abolished by alpha-methyldopa. In cats, dogs and rats, pressor responses to noradrenaline were usually slightly increased by alpha-methyldopa. Pressor responses to tyramine were not affected consistently. alpha-Methyldopa, alpha-methyldopamine and alpha-methylnoradrenaline behaved like dopa, dopamine and noradrenaline respectively in restoring the responses of tissues from reserpine-treated animals to stimulation of the sympathetic nerves to the rabbit ileum, the guinea-pig vas deferens and the cat nictitating membrane and in restoring responses to tyramine of the cat blood pressure and nictitating membrane, and the rat blood pressure. The potency of alpha-methylnoradrenaline relative to noradrenaline ranged from one-half to one-ninth on various preparations. The results are discussed in relation to the antihypertensive action of alpha-methyldopa.

Comparative studies of guanfacine and methyldopa

1. The antihypertensive effects of the new phenylacetylguanidine compound, guanfacine, a sympathetic inhibitor with a central site of action, were compared with methyldopa in 20 out-patients with essential or renal hypertension (WHO grade I-II). 2. During a 6-week period in randomized cross-over conditions, guanfacine 3.5 mg daily caused a mean decrease of 24% in mean arterial blood pressure (MAP). A normalization of blood pressure (BP < 145/95 mm Hg) was achieved in 50% of the patients and a 'good control' (BP < 160/100 mm Hg; > 145/95 mm Hg) in 90%. 3. Methyldopa 1.2 g daily led to a mean decrease in MAP of 12%. Normalization of blood pressure occurred in 15% and a 'good control' was achieved with 45% of the patients. Failure due to intolerance or ineffectiveness was observed in 40% of patients. 4. During therapy with guanfacine the following side-effects were noted: dryness of the mouth (n = 5), marked sedation (n = 2), constipation (n = 2), orthostasis (n = 1), collapse (n = 1) and atrioventricular block grade I on ECG (n = 1). Methyldopa caused headaches (n = 4), gastrointestinal disturbances (n = 4) and dryness of the mouth (n = 1). 5. The experience so far available seems to indicate that guanfacine is an effective antihypertensive drug which is more active than methyldopa in the doses used in this study.

Comparative study of metoprolol and alpha-methyldopa in untreated essential hypertension

The hypotensive actions of metoprolol and alpha-methyldopa have been compared in 37 men with previously untreated essential hypertension; 36 belonged to stage 1 and 1 to stage 2 of the WHO classification. After four weeks of placebo treatment the patients were randomly allocated to treatment with either of the two drugs. Treatment was started with metoprolol 75 mg daily or alpha-methyldopa 375 mg and was doubled after eight weeks. Satisfactory blood pressure control was defined as systolic blood pressure below 160 mm Hg and diastolic below 95 mm Hg. The patients were examined every four weeks and in those with unsatisfactory control the dose was gradually increased up to a maximum daily dose of metoprolol 450 mg or alpha-methyldopa 2250 mg. The trial lasted for 24 weeks after randomization. Five patients dropped out of the study. After six months, satisfactory blood pressure control was recorded in 16 out of 17 patients and 14 out of 15 patients treated with metoprolol and alpha-methyldopa, respectively. The average reduction in blood pressure produced by the two drugs was comparable. One patient in the alpha-methyldopa group developed drug exanthema and two patients a positive Coombs' test. Other side effects were few and did not differ between the two compounds.