Clonidine stimulates alpha-2 receptors in brain stem which results in reduced sympathetic outflow from the CNS and a decrease in peripheral resistance leading to reduced BP and pulse rate. It does not alter normal haemodynamic response to exercise at recommended dosages.

Onset
2-3 days (transdermal).

Duration
Maintained for 8 hours after removal of system (transdermal).

Absorption
Well absorbed from the GI tract (oral); peak plasma concentrations after 3-5 hours. Absorbed from the skin (transdermal).

Distribution
20-40% protein bound.

Metabolism
Hepatic: 50% of the dose.

Excretion
Via urine within 24 hours (as 40-60% as unchanged drug), via faeces (20% of the dose); 6-24 hours (elimination half-life), prolonged to 41 hours in renal impairment.

Information Not Available

Dry mouth, drowsiness, dizziness, headache, constipation, impotence, vivid dreams, urinary retention; dry, itching, burning sensation in the eye; fluid or electrolyte imbalance, GI upset, paralytic ileus, orthostatic hypotension, weakness, sedation, pruritus, myalgia, urticaria, nausea, insomnia, arrhythmias, agitation. Reduced GI motility at times may cause paralytic ileus.

Potentially Fatal: Transient hypertension or profound hypotension, respiratory depression, convulsion. Clonidine withdrawal syndrome could be life threatening. Bradycardia, coma and disturbances in conduction (in individuals with preexisting diseases of SA/AV nodes, overdose or on digitalis).

General
In patients who have developed localized contact sensitization to transdermal Clonidine, continuation of transdermal Clonidine or substitution of oral Clonidine hydrochloride therapy may be associated with the development of a generalized skin rash.
In patients who develop an allergic reaction to transdermal Clonidine, substitution of oral Clonidine hydrochloride may also elicit an allergic reaction (including generalized rash, urticaria, or angioedema).

Clonidine hydrochloride should be used with caution in patients with severe coronary insufficiency, conduction disturbances, recent myocardial infarction, cerebrovascular disease or chronic renal failure.

Perioperative Use: Administration of Clonidine hydrochloride should be continued to within four hours of surgery and resumed as soon as possible thereafter. Blood pressure should be carefully monitored during surgery and additional measures to control blood pressure should be available if required.

Withdraw gradually, renal impairment, tasks that require mental alertness. Cerebrovascular disease, ischaemic heart disease, MI. IV injection should be administered slowly. Occlusive peripheral vascular disorders, history of depression.

Hypotensive action may be potentiated by diuretics and vasodilators. Effects of clonidine antagonised by TCAs and centrally-acting alpha-blockers. May enhance toxicity due to digitalis, lithium. May antagonise oral hypoglycaemics.

Potentially Fatal: Hypnosedatives, antihistamines and alcohol may cause excessive drowsiness in patients on clonidine. Withdrawal of clonidine in patients receiving noncardioselective β-blockers may result in rebound BP. Acute severe hypotension following concomitant administration of clonidine and chlorpromazine or haloperidol.

Information Not Available

Oral
Hypertension
Adult: Initially, 50-100 mcg tid. As modified-release preparation: 50-100 mcg once or twice daily. Max: 2400 mcg daily.
Child: 2–18 years: Initially 0.5–1 mcg/kg tid, increase gradually if necessary. Max: 25 mcg/kg daily in divided doses (not exceeding 1.2 mg daily).

Renal impairment: Supplemental doses after haemodialysis are not necessary.
CrCl (ml/min)  Dosage Recommendation
<10                50-75% of usual dose.

Oral
Migraine
prophylaxis
Adult: 50 mcg bid increased to 75 mcg bid if no remission after 2 weeks.
Renal impairment: Supplemental doses after haemodialysis are not necessary.
CrCl (ml/min) Dosage Recommendation
<10           50-75% of usual dose

Oral
Menopausal flushing
Adult: 50 mcg bid increased to 75 mcg bid if no remission after 2 weeks.

Renal impairment: Supplemental doses after haemodialysis are not necessary.
CrCl (ml/min) Dosage Recommendation
<10               50-75% of usual dose

Intravenous
Hypertensive crisis
Adult: 150-300 mcg by slow injection over 10-15 minutes. Max: 750 mcg over 24 hours.
Child: 2–18 years: 2–6 mcg/kg as a single dose. Max: 300 mcg.

Renal impairment: Supplemental doses after haemodialysis are not necessary.
CrCl (ml/min)  Dosage Recommendation
<10                50-75% of usual dose.

Transdermal
Hypertension
Adult: Apply a patch once weekly, delivering 100-300 mcg of clonidine base daily at a constant rate.

Renal impairment: Supplemental doses after haemodialysis are not necessary.
CrCl (ml/min) Dosage Recommendation
<10               50-75% of usual dose.

Epidural
Severe cancer pain
Adult: Initially, 30 mcg/hour as continuous infusion in combination with an opioid, adjusted according to patient's response.

May be taken with or without food

Contraindicated in pregnancy.

Category C: Either studies in animals have revealed adverse effects on the foetus (teratogenic or embryocidal or other) and there are no controlled studies in women or studies in women and animals are not available. Drugs should be given only if the potential benefit justifies the potential risk to the foetus.

Contraindicated in lactation

Safety and effectiveness in pediatric patients below the age of twelve have not been established.

Information Not Available

Hypersensitivity. Disorders of cardiac pacemaker activity and conduction. Pregnancy and lactation.

Epidural
Store below 30°C.

Intravenous
Store below 30°C.

Oral
Store below 30°C.

Transdermal
Store below 30°C.

Transient abnormalities in liver function tests