HY-PO-TONE® 250
HY-PO-TONE® 500
SCHEDULING STATUS:
S3
PROPRIETARY NAME
(and dosage form):
HY-PO-TONE® 250
HY-PO-TONE® 500
COMPOSITION:
Each tablet contains 250mg or 500mg anhydrous methyldopa.
PHARMACOLOGICAL CLASSIFICATION:
A 7.1 3 Other hypotensives.
PHARMACOLOGICAL ACTION:
The exact mechanism of pharmacological action is not known. It may involve stimulation of central alpha-adrenergic receptors by a metabolite, alpha-methylnorepinephrine, thus inhibiting sympathetic outflow to the heart, kidneys and peripheral vasculature. Reduced peripheral resistance and plasma renin activity may also contribute to its effect.
INDICATIONS:
Methyldopa is indicated in the treatment of essential hypertension.
CONTRA-INDICATIONS:
Methyldopa is contra-indicated in persons known to be sensitive to it. It should be used with caution in patients with impaired kidney or liver function or with a history of liver disease or mental depression. It should not be given to patients with acute liver disease or phaeochromocytoma. It is contra-indicated during pregnancy. Methyldopa has been reported to aggravate porphyria.
DOSAGE AND DIRECTIONS FOR USE:
Doses of 0,25g two or three times daily during the first 48hours. Thereafter, the daily dosage may be adjusted preferably at intervals of not less than 48hours, until an adequate response has been achieved. The usual dose is from 0,5g –2g daily. A suggested initial dose for children is 10mg/kg body mass daily in divided doses.
SIDE-EFFECTS AND SPECIAL PRECAUTIONS:
The most common side-effect of methyldopa is drowsiness in the first 2 or 3days; this usually decreases spontaneously or as a result of a reduction in the dosage.
Other common side-effects include depression, psychic effects, impaired mental acuity, nightmares, nausea, dryness of the mouth, nasal stuffiness, weakness, dizziness, light-headedness, headache, oedema and disorders of sexual function. More rarely, black or sore tongue, breast enlargement, lactation, hyperprolactinaemia, pancreatitis, salivary gland inflammation, paraesthesia, Bell's palsy, parkinsonism, gastro-intestinal upsets, diarrhoea, constipation, fever, mild arthralgia, myalgia, uraemia, myocarditis, and aggravation of angina pectoris may occur. There may be bradycardia or hypotension. Involuntary choreoathetotic movements have occurred in patients with severe bilateral cerebrovascular disease. Eczematous rashes and lichenoid and granulomatous skin eruptions have occurred.
Thrombocytopenia, leucopenia, granulocytopenia, and haemolytic anaemia have also been reported. A positive response to the direct Coombs' test may occur in 10 to 20% of patients on prolonged therapy, usually without evidence of haemolysis. Fever may occur within the first few weeks of therapy and may be accompanied by eosinophilia and abnormal liver function tests. Jaundice with or without fever may occur. Liver damage may also develop after long-term administration and, rarely, fatal hepatic necrosis has been reported. A condition resembling systemic lupus erythematosus has been reported.
Methyldopa may occasionally cause urine to darken because of the breakdown of the drug or its metabolites.
Severe hypotension may occur during anaesthesia in patients being treated with methyldopa. The hypotensive effects may be diminished by sympathomimetics, imipramine and other tricyclic antidepressants, and mono-amine oxidase inhibitors. Mass gain and oedema may be diminished by the concomitant administration of a thiazide diuretic such as chlorothiazide. It is advisable to take blood counts and to perform liver-function tests at intervals during the first 6 –12weeks of treatment or if the patient develops an unexplained fever.
Interactions:
The hypotensive effects of methyldopa are enhanced by thiazide diuretics and other hypertensive agents. Methyldopa may interfere with the measurement of urinary uric acid by the phosphotungstate method and serum glutamic-pyruvic transaminase by the colorimetric method. Methyldopa fluoresces at the same wavelengths as catecholamines and may cause erratic reports of elevated urinary catecholamine concentrations.
KNOWN SYMPTOMS OF OVERDOSAGE AND PARTICULARS OF ITS TREATMENT:
See "Side-effects and special precautions". Treatment is symptomatic and supportive.
If overdosage occurs the stomach should be emptied by aspiration and lavage. Treatment is largely symptomatic, but if necessary, intravenous infusions may be given to promote urinary excretion, and pressor agents given cautiously. Methyldopa is dialysable.
IDENTIFICATION:
Yellow, biconvex film-coated tablet. The 250mg tablet has "HPT" engraved on the one side.
PRESENTATION:
Packs of 100 and 500 tablets.
STORAGE INSTRUCTIONS:
Store below 25°C.
Keep the container tightly closed.
Protect from light and dispense in amber bottles.
KEEP OUT OF REACH OF CHILDREN.
REGISTRATION NUMBERS:
250mg: K/7.1.3/90.
500mg: K/7.1.3/209.
NAME AND BUSINESS ADDRESS OF APPLICANT:
Pharmacare Limited, 7 Fairclough Road, PORT ELIZABETH 6001
DATE OF PUBLICATION OF THIS PACKAGE INSERT:
3.2.1979.
G855
A & S PRINTERS
Updated on this site: March 2000
Current: September 2004
Source: Community Pharmacy
