8.3 DRUG-ANAESTHETIC INTERACTION
Many old animals are kept on long-term treatments such
as non-steroidal anti-inflammatory drugs (NSAIDS), corticosteroids, diuretics, cardiac
stiulants and anticonvulsants. A pre-surgical review of medications is important because
they may affect anaesthesia.
Phenytoin and primidone are potentially hepatotoxic when
they interwith anaesthetic agents and they also cause CNS depression, so reducing
the dose of anaesthetic needed.
Chronic glucocorticoid administration may induce adrenal
insufficiency predisposing to cardiac instability during anaesthesia. This is another
reason why glucocorticoid administration immediately before induction of anaesthesia
has been advocated.
Long-term diuretic administration may cause metabolic
alkalosis, hypokalaemia, and sometimes hypomagnesaemia - all of which should be corrected