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Methyldopa

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

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Methyldopa is approximately 50% absorbed from the gut; it is metabolized in the intestines and liver; its metabolite alpha-methylnorepineprine acts in the brain to stimulate alpha-adrenergic receptors 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 If the drug is abruptly withdrawn, the "original" as well as "new" receptors become available and cause a severe reaction to the "normal" SNS activity (which is usually in excess).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.

Read more at Wikipedia.org


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Gynecomastia
From Gale Encyclopedia of Medicine, 4/6/01 by J. Ricker Polsdorfer

Definition

Gyne refers to female, and mastia refers to the breast. Gynecomastia is strictly a male disease and is any growth of the adipose (fatty) and glandular tissue in a male breast. Not all breast growth in men is considered abnormal, just excess growth.

Causes & symptoms

Breast growth is directed exclusively by female hormones--estrogens. Although men have some estrogen in their system, it is usually insufficient to cause much breast enlargement because it is counterbalanced by male hormones--androgens. Upsetting the balance, either by more of one or less of the other, results in the male developing female characteristics, breast growth being foremost.

At birth both male and female infants will have little breast buds from their mother's hormones. These recede until adolescence, when girls always, and boys sometimes, have breast growth. At this time, the boy's breast growth is minimal, often one-sided and temporary.

Extra or altered sex chromosomes can produce intersex problems of several kinds. Breast growth along with male genital development is seen in Klinefelter syndrome--the condition of having an extra X (female) chromosome--and a few other chromosomal anomalies. One of the several glands that produce hormones can malfunction for reasons other than chromosomes. Failure of androgen production is as likely to produce gynecomastia as overabundant estrogen production. Testicular failure and castration can also be a cause. Some cancers and some benign tumors can make estrogens. Lung cancer is known to increase estrogens.

If the hormone manufacturing organs are functioning properly, problems can still arise elsewhere. The liver is the principle chemical factory in the body. Other organs like the thyroid and kidneys also effect chemical processes. If any of these organs are diseased, a chemical imbalance can result that alters the manufacturing process. Men with cirrhosis of the liver will often develop gynecomastia from increased production of estrogens.

Finally, drugs can also cause breast enlargement. Estrogens are given to men to treat prostate cancer and a few other diseases. Marijuana and heroin, along with some prescription drugs, have estrogen effects in some men. On the list are methyldopa (for blood pressure), cimetidine (for peptic ulcers), diazepam (Valium), antidepressants, and spironolactone (a diuretic).

Diagnosis

Carefully feeling the area beneath the nipple of an adolescent boy with breast enlargement will reveal a discreet and sometimes tender lump the size of a fat nickel or quarter. For more serious gynecomastia, the underlying disease will require evaluation, if it is not already well understood.

Treatment

This condition is usually not treated. If it is the result of endocrine disease, hormone manipulations may reduce the effects of the imbalance. There are a number of medical and surgical interventions possible. Radiation of misbehaving organs and cancers is considered an effective treatment.

Prognosis

The progress of gynecomastia is determined by its cause.

Key Terms

Androgen
Male sex hormone.
Cirrhosis
Diffuse scarring caused by alcohol or chronic hepatitis often leading to liver failure.
Estrogen
Sex hormone responsible for stimulating female sexual characteristics.
Klinefelter syndrome
A condition in a male characterized by having an extra X (female) chromosome and suffering from infertility and gynecomastia.
Thyroid
A gland in the neck that makes thyroxin. Thyroxin regulates the speed of metabolism.

Further Reading

For Your Information

    Books

  • Bennett, J. Claude and Fred Plum, ed. Cecil Textbook of Medicine. Philadelphia: W. B. Saunders, 1996, pp. 1332-1333.
  • Fitzgerald, Paul A. "Endocrinology." In Current Medical Diagnosis and Treatment. Edited by Lawrence M. Tierney Jr., et al. Stamford, CT: Appleton & Lange, 1998, p. 1032.
  • Wilson, Jean D. "Endocrine disorders of the breast." In Harrison's Principles of Internal Medicine. Edited by Kurt Isselbacher, et al. New York: McGraw-Hill, 1997, pp. 111-115.

Gale Encyclopedia of Medicine. Gale Research, 1999.

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