Clonidine pharmacological activity

Clonidine is well absorbed after oral administration. Peak plasma levels occur between 2 and 4 hours after drug administration and correlate well with pharmacological activity. The plasma half-life in patients with normal renal function is 12 hours. Urinary excretion of clonidine and its metabolites accounts for almost 90% of the administered dose, and fecal excretion accounts for the rest. Approximately 50% of an administered dose is excreted unchanged the remainder is oxidatively metabolized in the liver. 

If these measures fail, clonidine, fluphenazine, clonazepam, or carbamazepine should be tried. The pharmacologic properties of these drugs are discussed elsewhere in this book. Clonidine reduces motor or vocal tics in about 50% of children so treated. It may act by reducing activity in noradrenergic neurons in the locus coeruleus. It is introduced at a dose of 2-3 mcg/kg/d, increasing after 2 weeks to 4 mcg/kg/d and then, if required, to 5 mcg/kg/d. It may cause an initial transient fall in blood pressure. The most common adverse effect is sedation other adverse effects include reduced or excessive salivation and diarrhea. Phenothiazines such as fluphenazine sometimes help the tics, as do dopamine... 

Answer A. Back to ANS pharmacology The release of insulin from the pancreas is stimulated by insulinogens (glucose), sulfonylurea hypoglycemics (glipizide), activators of beta, adrenoceptors (e.g., albuterol), and activators of muscarinic receptors (e.g., pilocarpine). The only receptor that, when activated, inhibits insulin release is the alpha2 receptor, which could be stimulated by clonidine or methyldopa. 

Boehnlein, J.K., Kinzie, J.D., 2007. Pharmacologic reduction of CNS noradrenergic activity in PTSD the case for clonidine and prazosin. J. Psychiatr. Pract. 13, 72-78. 

BS 110—141, N-amidino-2-(2,6-dichlo-rophenyljacetamide HCl is a guanidine derivative, but its pharmacological action resembles that of clonidine it possesses a central os-adrenoreceptor stimulant activity and causes a centrally induced fall in blood pressure, due probably to lowering of sympathetic activity and reduction of circulatory pressor reflexes. Apparently because of this, postural hypotension seems to be rare. In a series of 15 patients some general side effects were recorded and (surprisingly) the development of a tremor in 5 on a 3—6 mg daily dose (22 =). 

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