VPT 321: Veterinary Neuropharmacology (2+1) copy 1

PHARMACOKINETICS AND ADVERSE EFFECTS

• pKa between 8 and 9-mostly ionised at body pH.
• Given at a local site. Absorption and distribution not desired. If absorbed and distributed, may cause CNS and cardiac toxicity
• Vasoconstrictors ↓ absorption
• Ester type broken down by esterases while amide type – remain long acting
• Amide type – hydrolysed by Microsomal enzymes
• Metabolites excreted in urine
• Adverse effects –
• CNS – Initial stimulation → tremor, restlessness, convulsions and death
• Higher doses – depression
• Low non-seizure dose used for euphoria in man and to enhance performance in horses
• CVS - decrease myocardial contractility, rate and force of conduction – dilatation of the arterioles
• Renal and hepatic blood flow - decrease the blood fow to  liver and kidney so lower the metabolism and excretion