(and dosage form)
a) 10 mg Hydrallazine Hydrochloride
b) 50 mg Hydrallazine Hydrochloride.
A7.1.3 Other hypotensives.
The major action of hydrallazine is direct relaxation of vascular smooth muscle with a greater effect on arterioles than on veins. Therefore in adequate doses it decreases arterial blood pressure, diastolic often more than systolic, and peripheral vascular resistance, and increases heart rate, stroke volume, and cardiac output. The preferential dilatation of arterioles, minimizes postural hypotension and promotes the increase in cardiac output. The latter may limit the reduction in mean blood pressure produced by the drug. The peripheral vasodilatation is widespread but not uniform. Glomerular filtration, renal tubular function, and urine volume are not consistently affected; however, in common with many other hypertensive agents, hydrallazine can produce sodium retention and decreased urine volume. Hydrallazine usually increases plasma renin activity. Vascular resistance in the cutaneous and muscle beds may decrease, but this is usually in parallel with the fall in blood pressure and blood flow does not increase.
Effects of hydrallazine on organs other than those of the cardiovascular system are minor and variable.
Hydrallazine is used to reduce the blood pressure in hypertension.
Hydrallazine is contra-indicated in patients with tachycardia and should be used with caution in patients with a history of coronary disease.
The safety of this medicine in pregnant women has not yet been established.
DOSAGE AND DIRECTIONS FOR USE:
The usual oral dose is 100 to 200 mg per day, starting with 10 or 20 mg two to four times daily; this is increased gradually until the desired effect is obtained or unacceptable side-effects develop. The dose should not exceed 300 mg per day.
SIDE-EFFECTS AND SPECIAL PRECAUTIONS:
Side-effects occurring frequently are tachycardia, palpitations, angina, sweating, severe headache, anorexia, nausea, vomiting, diarrhoea and postural hypotension.
Side-effects occurring less frequently are conjunctivitis, lacrimation, chills, fever, vertigo, flushing, dyspnoea, malaise, muscle cramps and nasal congestion. Occasionally, hepatitis, local oedema, urinary retention, emotional depression, paralytic ileus, anxiety and tremor occur. Rarely drug fever, urticaria, skin rash, polyneuritis, gastro-intestinal haemorrhage, anaemia and pancytopenia occurs and require termination of therapy.
The safety of this preparation in pregnant women has not been established.
Chronic administration of hydrallazine, particularly in doses of 400 mg or more per day, can produce an acute rheumatoid state. This has been reported in approximately 10% of patients receiving high doses and a syndrome indistinguishable from disseminated lupus erythematosus develops in a smaller percentage. The symptoms regress after hydrallazine is discontinued but relatively long-term treatment with adrenocorticosteroids may be required. Reduced doses of hydrallazine should be given to patients who are slow acetylators.
Hypotension may occur during anaesthesia in patients being treated with hydrallazine. Adrenaline should not be given to antagonise the hypotensive effects of hydrallazine since it enhances the cardiac-accelerating effects. Caution should be observed if hydrallazine is administered concurrently with monoamine oxidase inhibitors or tricyclic antidepressants. The hypotensive effects of hydrallazine may be enhanced by thiazide diuretics and by beta-adrenergic blocking agents which may also diminish the cardiac-accelerating effects.
KNOWN SYMPTOMS OF OVERDOSAGE AND PARTICULARS OF ITS TREATMENT:
Tachycardia, palpitations, severe headache, anorexia, nausea, vomiting, postural hypotension, lacrimation, nasal congestion and peripheral neuritis.
Empty the stomach by aspiration and lavage. Treatment for tachycardia and relative hypovolaemia may be indicated.
CONDITIONS OF REGISTRATION:
May be advertised to the professions only.
10 mg tablet: Off-white to pale yellow flat, bisected tablet with bevelled edges, engraved with mortar and pestle on one side.
50 mg tablet: Pink sugar-coated tablet.
Packs of 30, 100 and 500 tablets.
Store below 25°C.
Protect from light and moisture.
KEEP OUT OF REACH OF CHILDREN.
10 mg tablet: M/7.1.3/39
50 mg tablet: M/7.1.3/40
NAME AND BUSINESS ADDRESS OF APPLICANT:
7 Fairclough Road
PORT ELIZABETH 6001.
DATE OF PUBLICATION OF THIS PACKAGE INSERT:
Current: March 2005
Source: Hospital Pharmacy
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