Guanethidine


Concise Prescribing Info
Indications/Uses
Listed in Dosage.
Dosage/Direction for Use
Adult : PO HTN 10 mg/day. May increase slowly. Maintenance: 25-50 mg once daily. IM Hypertensive crisis 10-20 mg as a single dose. Ophth Open-angle glaucoma; Lid retraction in hyperthyroidism As 5% soln: Apply as directed.
Dosage Details
Intramuscular
Hypertensive crisis
Adult: As monosulfate: 10-20 mg as a single dose.

Ophthalmic
Open-angle glaucoma
Adult: As monosulfate: 5% eye drops without adrenaline or, 1% or 3% with adrenaline 0.2% or 0.5%, respectively.

Ophthalmic
Lid retraction accompanying hyperthyroidism
Adult: As monosulfate: 5% eye drops.

Oral
Hypertension
Adult: As monosulfate: 10 mg daily, increased by increments of 10 mg every 5-7 days according to response. Maintenance: 25-50 mg once daily .
Child: As monosulfate: 200 mcg/kg daily with increments of 200 mcg/kg every 7-10 days, according to response.
Contraindications
Pheochromocytoma; heart failure not caused by hypertension.
Special Precautions
Renal impairment, cerebrovascular disorders, ischaemic heart disease, history of peptic ulcer or asthma. Hypotensive effect may be increased by exercise and heat. Increased risk of CV collapse or cardiac arrest in patients undergoing surgery. Eye drops: Examine regularly for signs of conjunctival damage.
Adverse Reactions
Severe postural and exertional hypotension, diarrhoea, dizziness, syncope, muscle weakness, lassitude, angina, renal insufficiency, transient cerebral ischaemia, bradycardia, failure of ejaculation, fatigue, headache, salt and water retention, oedema, breathlessness, overt heart failure, nausea, vomiting, dry mouth, nasal congestion, parotid tenderness, blurring of vision, depression, myalgia, muscle tremor, paresthesias, hair loss, dermatitis, disturbed micturition, priapism, aggravation or precipitation of asthma, exacerbation of peptic ulcer, haematological effects. Eye drops: Conjunctival hyperaemia, miosis, burning sensations, ptosis, superficial punctate keratitis.
Drug Interactions
Adrenaline, amphetamine, other sympathomimetics, tricyclic antidepressants, MAOIs, phenothiazine derivatives and related antipsychotics, oral contraceptives, digoxin or other digitalis derivatives, thiazide diuretics, other antihypertensives, levodopa, alcohol.
Action
Description: Guanethidine acts by selectively inhibiting transmission in postganglionic adrenergic nerves. It acts mainly by preventing the release of noradrenaline at nerve endings. It does not prevent catecholamine secretion by the adrenal medulla. When applied topically to the eye, guanethidine reduces the production of aqueous humor.
Pharmacokinetics:
Absorption: Absorption from GI tract is variable and incomplete absorbed; <50% of the dose reaches the systemic circulation.
Metabolism: Partially metabolised in the liver.
Excretion: Urine as metabolites and unchanged guanethidine. Terminal half-life: About 5 days.
Storage
Store <30°C.
Disclaimer: This information is independently developed by MIMS based on Guanethidine from various references and is provided for your reference only. Therapeutic uses, prescribing information and product availability may vary between countries. Please refer to MIMS Product Monographs for specific and locally approved prescribing information. Although great effort has been made to ensure content accuracy, MIMS shall not be held responsible or liable for any claims or damages arising from the use or misuse of the information contained herein, its contents or omissions, or otherwise. Copyright © 2020 MIMS. All rights reserved. Powered by MIMS.com
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