Dopaflex

Indications

Methyldopa is used to treat high blood pressure. It is especially used for high blood pressure during pregnancy, because it has a long record of safety for the unborn baby.

How It Works

Methyldopa is changed in the brain into a substance that stimulates alpha-2 receptors. This reduces the nerve signals from the brain that tighten blood vessels, so the vessels relax and blood pressure falls.

Dosage and Administration

Take as prescribed. Adults usually start with 250 mg two or three times a day for the first 2 days. The doctor then adjusts the dose every few days, usually up to 0.5 to 2 g a day in divided doses, with a maximum of 3 g a day. Older people often need lower doses. An increase in dose is often started with the evening dose because it can cause drowsiness. Do not stop suddenly.

Interactions

Iron supplements (Ferrous Sulphate or Ferrous Gluconate) can reduce its effect, so take them at different times. Other blood pressure medicines and anaesthetics can add to its effect. It can increase Lithium toxicity. It must not be used with MAO inhibitors. Alcohol and sedatives can increase drowsiness.

Contraindications

Do not use if you are allergic to Methyldopa; if you have active liver disease, or had liver problems with Methyldopa before; if you have depression; if you have phaeochromocytoma (an adrenal tumour); if you have porphyria; or if you take MAO inhibitors.

Side Effects

Common side effects include drowsiness, tiredness, headache, weakness, dizziness on standing, dry mouth, stuffy nose, swelling of the ankles and low mood. Less often it causes sexual problems, slow heartbeat, or breast enlargement. Blood tests may show a positive Coombs test, which is usually harmless but can rarely lead to breakdown of red blood cells.

Get urgent medical help if you have yellowing of the skin or eyes, dark urine, fever without a clear cause, unusual tiredness with paleness or breathlessness, severe depression or thoughts of self-harm, or swelling of the face or throat.

Pregnancy and Lactation

Methyldopa is one of the preferred medicines for high blood pressure in pregnancy and is used under medical supervision. Small amounts pass into breast milk; it is generally considered compatible with breastfeeding, but it can worsen low mood after delivery, so your doctor may switch to another medicine after birth.

Precautions and Warnings

Your doctor may check liver tests and blood counts, especially in the first months. Tell the laboratory you take it before a blood transfusion cross-match. Use with care if you have kidney or liver disease or a history of depression. It may cause drowsiness: take care with driving at the start of treatment or after a dose increase.

Overdose

Overdose can cause very low blood pressure, extreme drowsiness, slow heartbeat, weakness, dizziness and constipation. Seek emergency medical help.

Therapeutic Class

Antihypertensive, centrally acting alpha-2 adrenergic agonist.

Storage

Store below 30°C in a dry place, away from light and out of the reach of children.