Side Effects of Aldomet (methyldopa)

Aldomet (methyldopa) is an antihypertensive medication used to lower blood pressure. 

Although the exact mechanism of action is not yet understood, Aldomet is thought to lower blood pressure by activating receptors (alpha-2 receptors) in the central nervous system and by reducing the concentration of the neurotransmitters epinephrine, norepinephrine, dopamine, and serotonin. 

Reducing the concentration of these neurotransmitters causes blood vessels to dilate (relax or widen), and, as a result, blood pressure is reduced. After oral administration maximum reduction in blood pressure occurs in four to six hours. 

When patients reach an effective dosage, a smooth blood pressure response usually occurs in 12 to 24 hours. Blood pressure usually returns to pretreatment levels 24 to 48 hours after stopping treatment because Aldomet is eliminated from the body quickly.

Common side effects of Aldomet include

• dizziness,
• lightheadedness,
• drowsiness,
• headache,
• stuffy nose, and
• weakness, especially when starting Aldomet and when dosage is increased.

Serious side effects of Aldomet include

• anemia (low red blood cell count),
• water retention (edema or swelling of the legs) or weight gain, and
• high blood pressure (hypertension) in certain dialysis patients and in patients with cerebrovascular disease.

Drug interactions of Aldomet include monoamine oxidase inhibitors (MAOIs), a class of medications used to treat depression, because combining these drugs with Aldomet may lead to dangerous side effects. 

Administration of Aldomet with iron supplements including ferrous sulfate and ferrous gluconate is not recommended as coadministration may decrease blood levels of Aldomet. 

Patients taking Aldomet may require reduced doses of anesthetics during surgical procedures because of the risk of low blood pressure (hypotension). 

The safety of Aldomet in pregnant women has not been adequately evaluated. 

Aldomet is known to enter breast milk. It should be used cautiously in breastfeeding mothers.

WARNING

• Methyldopa may cause anemia (low number of red blood cells). Before starting treatment, doctors may order certain blood tests to check blood levels of red blood cells. Additionally, periodic blood tests should be done during treatment to detect hemolytic anemia (spontaneous break-down of red blood cells). Methyldopa should be discontinued if hemolytic anemia occurs during treatment.
• Methyldopa should be used cautiously in patients who have a history of liver disease and should be avoided in patients with active liver disease including acute hepatitis and active cirrhosis.
• Methyldopa may cause water retention (edema or swelling of the legs) or weight gain in some patients and, therefore, should be used cautiously in heart failure patients.
• Methyldopa is removed by certain types of dialysis procedures. In certain dialysis patients, hypertension (high blood pressure) has occurred as a result of methyldopa being removed from the body during dialysis.
• Methyldopa should be used cautiously in patients with cerebrovascular disease because involuntary movements have been observed during treatment.

Sedation, usually transient, may occur during the initial period of therapy or whenever the dose is increased. Headache, asthenia, or weakness may be noted as early and transient symptoms. However, significant adverse effects due to Aldomet (methyldopa) have been infrequent and this agent usually is well tolerated.

The following adverse reactions have been reported and, within each category, are listed in order of decreasing severity.

Cardiovascular: Aggravation of angina pectoris, congestive heart failure, prolonged carotid sinus hypersensitivity, orthostatic hypotension (decrease daily dosage), edema or weight gain, bradycardia.

Digestive: Pancreatitis, colitis, vomiting, diarrhea, sialadenitis, sore or "black" tongue, nausea, constipation, distension, flatus, dryness of mouth.

Endocrine: Hyperprolactinemia.

Hematologic: Bone marrow depression, leukopenia, granulocytopenia, thrombocytopenia, hemolytic anemia; positive tests for antinuclear antibody, LE cells, and rheumatoid factor, positive Coombs test.

Hepatic: Liver disorders including hepatitis, jaundice, abnormal liver function tests.

Hypersensitivity: Myocarditis, pericarditis, vasculitis, lupus-like syndrome, drug-related fever, eosinophilia.

Nervous System/Psychiatric: Parkinsonism, Bell's palsy, decreased mental acuity, involuntary choreoathetotic movements, symptoms of cerebrovascular insufficiency, psychic disturbances including nightmares and reversible mild psychoses or depression, headache, sedation, asthenia or weakness, dizziness, lightheadedness, paresthesias.

Metabolic: Rise in BUN.

Musculoskeletal: Arthralgia, with or without joint swelling; myalgia.

Respiratory: Nasal stuffiness.

Skin: Toxic epidermal necrolysis, rash.

Urogenital: Amenorrhea, breast enlargement, gynecomastia, lactation, impotence, decreased libido.

When methyldopa is used with other antihypertensive drugs, potentiation of antihypertensive effect may occur. Patients should be followed carefully to detect side reactions or unusual manifestations of drug idiosyncrasy.

Patients may require reduced doses of anesthetics when on methyldopa. If hypotension does occur during anesthesia, it usually can be controlled by vasopressors. The adrenergic receptors remain sensitive during treatment with methyldopa.

When methyldopa and lithium are given concomitantly the patient should be carefully monitored for symptoms of lithium toxicity. Read the circular for lithium preparations.

Several studies demonstrate a decrease in the bioavailability of methyldopa when it is ingested with ferrous sulfate or ferrous gluconate. This may adversely affect blood pressure control in patients treated with methyldopa. Coadministration of methyldopa with ferrous sulfate or ferrous gluconate is not recommended.

Monoamine oxidase (MAO) inhibitors: See prescription labeling.

Drug/Laboratory Test Interactions

Methyldopa may interfere with measurement of: urinary uric acid by the phosphotungstate method, serum creatinine by the alkaline picrate method, and SGOT by colorimetric methods. Interference with spectrophotometric methods for SGOT analysis has not been reported.

Since methyldopa causes fluorescence in urine samples at the same wave lengths as catecholamines, falsely high levels of urinary catecholamines may be reported. This will interfere with the diagnosis of pheochromocytoma. It is important to recognize this phenomenon before a patient with a possible pheochromocytoma is subjected to surgery.

Methyldopa does not interfere with measurement of VMA (vanillylmandelic acid), a test for pheochromocytoma, by those methods which convert VMA to vanillin. Methyldopa is not recommended for the treatment of patients with pheochromocytoma. Rarely, when urine is exposed to air after voiding, it may darken because of breakdown of methyldopa or its metabolites.