Aldomet (Methyldopa): A Guide to Uses, Dosage, and Safety

Disclaimer: This information is for educational purposes only and should not be considered medical advice. Always consult with a qualified healthcare professional before making any decisions about your health or treatment, especially concerning blood pressure management.

Aldomet® (Methyldopa)

Summary

Aldomet, with the active ingredient Methyldopa, is a well-established antihypertensive medication used to treat high blood pressure (hypertension). It works by acting on the central nervous system to relax blood vessels, which in turn lowers blood pressure. Aldomet is particularly known for its safety profile in treating hypertension during pregnancy, making it a preferred choice in this specific population. It helps control high blood pressure but does not cure it, and it is crucial for preventing serious complications such as strokes, heart attacks, and kidney problems.

Manufacturer

KAHIRA PHARM. & CHEM. IND. CO., Cairo - Egypt.

Category & Active Ingredient

• Category: Antihypertensive, Central Alpha-2 Adrenergic Agonist.
• Active Ingredient: Methyldopa.

Available Forms & Strengths in Egypt

Aldomet is available in the following oral tablet formulations:

• Aldomet 250 mg: Film-coated tablets, available in packs of 30.
• Aldomet 500 mg: Film-coated tablets, available in packs of 20.

Properties and Mechanism of Action

Methyldopa is a centrally-acting alpha-2 adrenergic agonist. After crossing the blood-brain barrier, it is metabolized in the central nervous system into alpha-methylnorepinephrine. This active metabolite stimulates central alpha-2 adrenergic receptors, which leads to a reduction in sympathetic outflow from the brain. The result is decreased peripheral vascular resistance and a reduction in blood pressure, typically without significantly affecting heart rate or cardiac output. Unlike many other antihypertensives, Aldomet generally does not compromise renal blood flow.

Indications

The primary indication for Aldomet is the treatment of moderate to severe hypertension. It is often considered a first-line treatment for managing high blood pressure during pregnancy (gestational hypertension) due to its established safety record for both the mother and the developing fetus. [1]

Dosage and Administration

Dosage must be individualized by a healthcare professional. Treatment is often started with a low dose, which is gradually increased to achieve the desired blood pressure control.

• Adults (Initial Therapy): The usual starting dose is 250 mg, two to three times a day for the first 48 hours. The dose may then be gradually increased or decreased, preferably at intervals of not less than two days, until an adequate response is achieved. The maximum recommended daily dose is 3 grams (3000 mg).
• Adults (Maintenance Therapy): The usual maintenance dosage is 500 mg to 2 g daily, given in two to four divided doses.
• Children: The initial daily dosage is based on weight, starting at 10 mg/kg of body weight daily in 2-4 divided doses. The maximum daily dose is 65 mg/kg or 3 g, whichever is less.

Aldomet can be taken with or without food. It is important to take the medication consistently as prescribed.

Side Effects

While effective, Aldomet can cause a range of side effects. Many of these are transient and may occur at the beginning of treatment or when the dose is increased.

• Central Nervous System: The most common side effect is sedation or drowsiness. Other effects include headache, weakness (asthenia), dizziness, lightheadedness, symptoms of cerebrovascular insufficiency, paresthesias, Bell's palsy, involuntary movements, and psychiatric disturbances like nightmares or mild psychoses and depression.
• Cardiovascular: Bradycardia (slow heart rate), prolonged carotid sinus hypersensitivity, aggravation of angina pectoris, and orthostatic hypotension (dizziness upon standing). Fluid retention (edema) and weight gain may also occur, which usually respond to diuretic therapy.
• Gastrointestinal: Nausea, vomiting, distension, constipation, flatus (gas), diarrhea, mild dryness of the mouth, sore or "black" tongue, pancreatitis, and sialadenitis (inflammation of a salivary gland).
• Hepatic (Liver): Liver disorders including hepatitis, jaundice, and abnormal liver function tests.
• Hematological (Blood): Positive Coombs test, hemolytic anemia, bone-marrow depression, leukopenia, granulocytopenia, thrombocytopenia.
• Allergic: Drug-related fever, lupus-like syndrome, myocarditis, pericarditis.
• Dermatological (Skin): Rash as in eczema or lichenoid eruption, toxic epidermal necrolysis.
• Other: Nasal stuffiness, rise in BUN, breast enlargement, gynecomastia, lactation, amenorrhea, impotence, decreased libido, and mild arthralgia (joint pain).

Contraindications

Aldomet should not be used in patients with:

• Active liver disease, such as acute hepatitis or active cirrhosis.
• A history of liver disorders previously associated with methyldopa therapy.
• Hypersensitivity to Methyldopa or any component of the product.
• Concurrent therapy with Monoamine Oxidase (MAO) Inhibitors.

Drug Interactions

Aldomet can interact with other medications, potentially altering its effects or increasing the risk of side effects.

• Other Antihypertensives: May have an additive effect, requiring dosage adjustments.
• Lithium: Concurrent use can increase the risk of lithium toxicity.
• MAO Inhibitors: Contraindicated due to the risk of excessive blood pressure elevation.
• Iron Supplements (e.g., Ferrous Sulfate): Can decrease the absorption of methyldopa, potentially reducing its effectiveness. It is advisable to separate the administration times.
• Anesthetics: Patients on Aldomet may require reduced doses of anesthetics.

Precautions & Warnings

• Liver Function: Liver function tests should be performed periodically, especially during the first 6 to 12 weeks of therapy or whenever an unexplained fever occurs, as methyldopa can cause serious liver injury.
• Blood Counts: Hemolytic anemia is a rare but serious side effect. A positive Coombs test occurs in 10-20% of patients, though anemia is less common. Blood counts should be checked if a patient develops anemia.
• Pregnancy & Lactation: Aldomet has been used extensively under close medical supervision for the treatment of hypertension during pregnancy and appears to be safe for both mother and fetus. However, it does cross the placental barrier. Methyldopa is also excreted in breast milk, so caution should be exercised when administered to a nursing woman.
• Sedation: Aldomet can cause drowsiness, which may impair the ability to drive or operate heavy machinery.
• Sudden Withdrawal: Stopping the medication abruptly can lead to a rare but serious rebound hypertension. Withdrawal should always be done under medical supervision.

Overdosage

Acute overdosage may produce a sharp drop in blood pressure (acute hypotension) and other effects related to brain and gastrointestinal dysfunction (e.g., excessive sedation, weakness, slow heart rate, dizziness, constipation, distension, flatus, diarrhea, nausea, vomiting). Treatment is symptomatic and supportive. If ingestion was recent, gastric lavage or induced vomiting may reduce absorption. In the case of severe overdose, management includes careful attention to heart rate, blood volume, electrolyte balance, and kidney function.

Frequently Asked Questions (FAQ)

Is Aldomet safe to use during pregnancy?
Yes, Methyldopa (Aldomet) is widely considered one of the safest and most commonly prescribed medications for managing high blood pressure during pregnancy. However, its use must always be supervised by a healthcare professional. [2]

Why do I feel so tired after starting Aldomet?
Drowsiness or sedation is a very common side effect, especially when you first start taking the medication or after a dose increase. This effect usually lessens as your body gets used to the drug over time.

Can I stop taking Aldomet if my blood pressure is normal?
No. Do not stop taking Aldomet without consulting your doctor. High blood pressure often has no symptoms, and stopping the medication suddenly can cause your blood pressure to rise sharply, which is dangerous. It controls blood pressure but does not cure it.

What is the Coombs test mentioned in the leaflet?
The Coombs test is a blood test used to detect antibodies that act against red blood cells. Some patients taking methyldopa develop a positive Coombs test. In a small percentage of these patients, this can lead to hemolytic anemia, a condition where red blood cells are destroyed faster than they are made. Your doctor will monitor for this if necessary.

References

1. American College of Obstetricians and Gynecologists (ACOG): For clinical guidelines on managing hypertension in pregnancy. ACOG Practice Bulletin on Gestational Hypertension
2. U.S. National Library of Medicine (MedlinePlus): For comprehensive, patient-friendly drug information. Methyldopa - MedlinePlus Drug Information
3. Drug Information Pamphlet: Key information, particularly regarding dosage, side effects, and precautions, is also sourced from the internal leaflet provided with Aldomet® by KAHIRA PHARM. & CHEM. IND. CO.