This document discusses the mechanism of action, indications, pharmacokinetics, adverse effects, and contraindications of clonidine. Clonidine is an alpha-2 adrenergic receptor agonist that competitively blocks beta receptors in the heart and smooth muscle, lowering blood pressure without significantly affecting heart rate. It has indications for hypertension, preeclampsia, and controlled hypotension during anesthesia. Clonidine is rapidly absorbed orally but undergoes extensive liver metabolism; its half-life is 2.5-8 hours. Common adverse effects involve the central nervous system, cardiovascular system, gastrointestinal tract, and respiratory tract. Contraindications include bronchial asthma, heart failure, heart block, shock, severe

1. Ala’a Fadhel Hassan
Al Mahmoudia G. Hospital

2. Mechanism of action
Competitively blocks β-receptors within the myocardium
(β1) and within bronchial and vascular smooth muscle (β
2) and α1-receptors within vascular smooth muscle
Has some intrinsic β2-agonist activity
Produces a dose-dependent (at usual doses) decrease in
systemic arterial BP and systemic vascular resistance
without a substantial reduction in resting heart rate,
cardiac output, or stroke volume
Generally has little effect on sinus rate, intraventricular-
conduction, the His-Purkinje system, or duration of
the QRS complex

3. Indication
Hypertension
Severe Hypertension and Hypertensive
Crisis
Preeclampsia
Controlled Hypotension during Anesthesia
Angina
Tetanus
Unlabeled Uses(pheochromocytoma &
clonidine-withdrawal hypertension)

4. Pharmacokinetics
 Rapidly absorbed from GIT following oral
adm.(90-100%) still food both delay & increase
absorption of drug
 Absolute bioavailability ~25% (increase with
geriatric pt & pt. with hepatic impairment)
 It undergoes extensive liver metabolism &
elimination via biliary route (30%) & (55%) as
glucuronide conjugates
 T 50% average 2.5-8 hr., duration is dose
dependent (orally 8-24hr & I.V 2-4 hr)

5. Adverse effect
Mentioned adverse effects associated
with
CNS
CVS
GIT & hepatic
Genitourinary tract
 Respiratory tract
Dermatologic
EENT

6. Contraindications
Bronchial asthma; overt cardiac failure;
greater than first-degree heart block;
cardiogenic shock; severe
bradycardia; conditions associated
with severe and prolonged
hypotension; history of obstructive
airway disease, including asthma;
hypersensitivity to any component of
the product.