omposition
Each film-coated tablet contains Methyldopa® (anyhdrous)
Properties
The mechanism of action of Methyldopa® is probably due to its metabolite alphamethylnoradrenaline, which lowers arterial pressure by stimulation of central inhibitory alpha-adrenergic receptor, false neurotransmission, and/or reduction of plasma renin activity.
Methyldopa® reduces both standing and supine blood pressure. Variations in diurnal blood pressure, symptomatic postural hypotension and exercise hypotension rarely occur. Careful adjustment of dosage avoids morning hypotension and does not affect the control of afternoon blood pressure.
Methyldopa® has no direct effect on cardiac heart function, and does not reduces filtration fraction, renal blood flow or glomerular filtration rate. Methyldopa® may be given with caution to patients with renal dysfunction.
Indications
Methyldopa® tablets are indicated for the treatment of hypertension.
Dosage
Adults: The initial dose of Methyldopa® tablets is usually 250mg two or three times daily for two days. The dose may be increased at intervals of not less than two days by an additional 250-500mg daily until satisfactory control is achieved. The maximum recommended daily dosage is 3g. Methyldopa® is mainly excreted by the kidneys therefore patients with renal dysfunction may respond to lower doses.
The requirement of Methyldopa® may be reduced may be reduced by giving a thiazide diuretic concurrently: downward adjustment of dosage should likewise be made at intervals of less than 48 hours.
When patients are on other hypotensive agents and it is desired to change them over to Methyldopa®, drug interactions must be carefully watched for has to be adjusted to effect a smooth transition.
Methyldopa® may be used concurrently with Amiloride, Hydrochlorothiazide and beta-blocking agents.
Elderly: The initial dose should not exceed 250mg daily. This should be increased slowly as required but not to exceed a maximum daily dose of 2g.
Side-effects
The most frequent side-effect is sedation which may occur even at the starting dose level. It usually subsides after an effective maintenance dosage has been established. Depression may also occur and corrective treatment with tricyclic antidepressants may anragonise the therapeutic effect of Methyldopa®.
Serious side-effects due to Methyldopa® are rare and this agent is well tolerated.
The following reactions have been reported:
Allergic: Drug-related fever and lupus-like syndrome, myocarditis, pericarditis.
Cardiovascular: Bradycardia, porlonged carotid sinus hypersensitivity, aggrevation of angina pectoris, orthostatic hypotension and oedema.
Central nervous system: Sedation, asthenia or weakness, headache, paraesthesiae, parkinsonism, involuntary choreoatherotic movements, bell’s palsy, psychic disturbances, dizziness, light-headedness and symptoms of cerebrovascular insufficiency.
Dermatological: Rash as in eczema or lichenoid eruption, toxic epidermal necrolysis.
Gasto-intestinal: Nauseae, vomiting, consipation, distension, flatus, colitis, diarrhoea, dry mouth, sore or ‘black’ tongue, sialadenitis and pancreatitis
Hepatic: Liver disorders such as abnormal liver function tests, hepatitis and jaundice.
Haematological: Positive Coombs’ test, bone marrow depression, leucopenia, haemolytic anaemia, granulocytopenia, thromocytopenia, positive tests to LE cells, antinuclear antibody and rheumatoid factor.
Miscellaneous: Myalgia, mild arthralgia, decreased libido, nasal stuffiness, rise in blood urea, gynaecomastia, breast enlargment, hyperprolactinaemia, lactation amenorrhoea, failure in ejaculation and impotence.