Molecule of the Month September 1999 Text by First Year Student - C J Wilson Pembroke College - University of Oxford, Models by Karl Harrison, Chemisty IT Centre, Department of Chemistry, Universtiy of Oxford.

lonidine is a drug which is primarily used as an antihypertensive agent, however it now sees widespread use in a number of other fields eg as an additive to anaesthetics. (click on the colour 3D image below to view a interactive 3D chemical model)

Two of the most interesting uses for the drug though are in the treatment of alcohol and nicotine withdrawl and in the treatment of ADD (Attention Deficit Disorder). For the treatment of ADD it has been found to reduce hyperactivity especially in children. However, tolerance can develop for the drug and can lead to withdrawl symptoms when taken off the drug. It is usually necessary to continue taking the drug for some time after the condition for which it was prescribed has been cured.

Clonidine is delivered as Clonidinehydrochloride and is an imidazoine derivative and a mesomeric compound. It’s Chemical name is 2-(2,6-dichloro phenylamino)-2-imidazoline hydrochloride. It is a crystalline compound which is soluble in water, alcohol and lipids. When administered clonidine is transported by lipids by bonding to albumin and has a volume distribution of 2.1± 0.4L/kg. About 50% of the oral dose is metabolised by minor pathways in the liver.
 

Clonidine is administered orally, by transdemal patch or by epidirial injection. It works by stimulating the alpha-adrenergeric receptors in the brain stem. This reduces the sympathetic outflows from the central nervous system leading to a decrease in peripheral resistance, renal vascular resistance and blood pressure (after 30 to 60mins) .

Clonidine tablets were approved in October 1984 and are available in 0.1, 0.2, 0.3mg forms. The 0.1mg tablet is equivalent to 0.087mg of free base. In tablet form the active ingredient is mixed with SiO₂ , corn starch, calcium phosphate, gelatin, glycerin, lactose and magnesium strearate.

Common side effects include constipation, dizziness, drowsiness, dry eyes, dry mouth and nausea. There is also a slight risk of hallucinations. Clonidine should not be taken with depression, diabetes, heart disease, kidney disease or if pregnant, trying to become pregnant or breast feeding.
 
 

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