Symptoms: may include postural hypotension which may cause syncope, sinus bradycardia (although tachycardia has been observed), tiredness, dizziness, blurring of vision, muscular weakness, nausea, vomiting, severe diarrhoea and oliguria.
Treatment: "Interactions with other medicaments and other forms of interaction"). Sinus bradycardia can be treated with atropine, and diarrhoea with an anticholinergic agent.
"Interactions with other medicaments and other forms of interaction"); in such cases, Guanethidine Monosulphate Amdipharm may lead to the release of large quantities of catecholamines, which may cause a hypertensive crisis.
Patients with known hypersensitivity to guanethidine and related derivatives. Heart failure due to causes other than hypertension. Renal failure (creatinine clearance 10 to 40ml/min).
None known.
Side effects are often an indication of excessive dosage. The following effects may occur:
Central nervous system: Particularly at the start of treatment: dizziness, tiredness, lethargy, paraesthesia and headache. Occasional: blurred vision and depression. Rare: myalgia and muscular tremor.
Cardiovascular system: Postural hypotension (which may be associated with cerebral or myocardial ischaemia in severe cases) especially when getting up in the morning or after physical exertion, sick-sinus syndrome, oedema, exacerbation of intermittent claudication and bradycardia. Occasional: heart failure. Rare: angina pectoris.
Gastro-intestinal tract: Diarrhoea and gaseous distension. Occasional: vomiting, nausea and dry mouth. Rare: swelling of parotid glands.
Respiratory tract: Nasal congestion. Rare: asthma.
Urogenital system: Raised BUN levels or uraemia in patients with latent or manifest renal failure, and ejaculation disturbances.
Skin and hair: Occasional: dermatitis. Rare: hair loss.
Blood: Isolated reports of anaemia, leucopenia, and/or thrombocytopenia.
There are no pre-clinical data of relevance to the prescriber which are additional to those already included in other sections of the Summary of Product Characteristics.
Control of hypertensive crises, and to obtain more rapid blood pressure control.
Guanethidine Monosulphate Amdipharm is a peripheral sympathetic blocking drug which lowers blood pressure by depleting and inhibiting reformation of noradrenaline in postganglionic nerve endings. Guanethidine, being highly polar, does not cross the blood-brain barrier and is unlikely therefore to exert any effect on the central nervous system. In addition, guanethidine has no effect on the parasympathetic nervous system.
Guanethidine may be excreted more slowly in those patients with moderate to severely compromised renal function, therefore the potential for accumulation of the drug will be higher.
Heat and physical exertion may increase the antihypertensive effect of Guanethidine Monosulphate Amdipharm.
Guanethidine Monosulphate Amdipharm should be used with caution in patients with moderate renal insufficiency (creatinine clearance 41 to 65ml/min), or with coronary and/or cerebral arteriosclerosis; abrupt lowering of blood pressure should be avoided. Caution should be exercised in asthmatic patients or in patients with a history of gastro-intestinal ulceration.
The concurrent administration of guanethidine and β-blockers may provoke severe bradycardia.
When patients have to undergo surgery, it is recommended that treatment with Guanethidine Monosulphate Amdipharm be withdrawn a few days before the operation. To avoid excessive bradycardia during anaesthesia, it is advisable to premedicate with larger than usual doses of atropine.
After prolonged treatment with Guanethidine Monosulphate Amdipharm, latent heart failure may develop. This is due to salt and water retention, and mild negative inotropic and chronotropic effects. Concomitant administration of diuretics can readily correct this condition.
If patients develop fever, the dose of Guanethidine Monosulphate Amdipharm should be lowered.
Patients should be warned of the potential hazards of driving or operating machinery if they experience side effects such as dizziness, blurred vision or drowsiness.
Adults:
Guanethidine Monosulphate Amdipharm should be given by intramuscular injection."Contra-indications").
Children: not recommended.
Elderly: Clinical evidence would indicate that no special dosage regime is necessary, but concurrent coronary or cerebral insufficiency should be taken into account.
None
Administrative data
