b. Methyldopa
Supplied: Tablets: 125 mg, 250 mg, and 500 mg.
Dosage: 250 mg twice daily increasing over days or weeks to 250 mg three times daily; 500 mg twice or three times daily.
It is postulated that the action of tachycardia caused by alpha-blockers such as methyldopa is central in the brain, decreasing sympathetic impulse outflow.
Advice and Adverse Effects: Methyldopa should rarely, if ever, be used without diuretics, because it causes significant sodium and water retention. This drug is an effective antihypertensive agent when combined with a diuretic. Because of the potential side effects, methyldopa is now reserved for treatment of moderate and severe hypertension in combination with other agents that fail to achieve control. It is contraindicated with active liver disease or depression. This has been known to cause a mild hemolytic anemia, so blood counts are necessary from time to time. If the drug is stopped suddenly, the blood pressure often increases over the next 12 h to very high levels (rebound hypertension); therefore, discontinue the drug gradually. If the dose is increased too rapidly, a sudden drop in blood pressure resulting in dizziness or a fainting spell may occur. Other adverse effects include dizziness, sedation, and sexual dysfunction. Methyldopa has been used successfully for more than 25 years to treat pregnancy-induced hypertension. It has an important role in this setting because other agents except beta-blockers are contraindicated.

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