Methyldopa

Methyldopa or '''alpha-methyldopa''' (brand names '''Aldomet''', '''Apo-Methyldopa''', '''Dopamet''', '''Novomedopa''') is a centrally-acting antiadrenergic Antihypertensive medication.

Methyldopa is approximately 50% absorbed from the gut; it is metabolized in the Intestine s and Liver ; its metabolite alpha-methylnorepineprine acts in the Brain to stimulate Alpha-adrenergic Receptor s decreasing Total Peripheral Resistance . It is Excreted in Urine .

Methyldopa, in its active metabolite form, leads to increased alpha-2 receptor-mediated inhibition of SNS (centrally and peripherally), allowing PSNS tone to increase. Such activity leads to a decrease in total peripheral resistance (TPR) and Cardiac Output .

All drugs in this class can cause "rebound" hypertension due to an up-regulation of alpha-2 receptors while under the influence of the drug. If the drug is abruptly withdrawn, the "original" as well as "new" receptors become available and cause a severe reaction to the "normal" SNS activity (which is usually in excess). In other words, the SNS typically releases more Norepinephrine (NE) than is needed to activate receptors (leading to a sustained response), and extra receptors leads to an over-response (in this case mediated by alfa-2 receptors leading to vascular smooth muscle constriction = rebound hypertension).

When introduced it was a mainstay of antihypertensive therapy, but its use has declined, with increased use of other classes of agents. One of its important present-day uses is in the management of Pregnancy-induced Hypertension , as it is relatively safe in pregnancy compared to other antihypertensive drugs.

Side effects
(some of these are serious and need to be reported to a physician)

A possible side-effect of methyldopa is breast enlargement in men ( Gynecomastia ).
Hyper-prolactinaemia.
Many patients report Orthostatic Hypotension , which tends to improve over time.
Skin rashes.
Bruising.
Low white blood cells.
Thrombocytopenia (Low platelets).
Haemolytic anaemia: the direct Coombs Test may become positive.
Tiredness.
Depression.
Impotence.

This list is not complete.

Side effects are usually fewer if the dose is less than 1 gm per day.

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Methyldopa