The in vitro uptake and metabolism of lignocaine, procainamide and pethidine by tissues of the hindquarters of sheep.

1. In vitro studies using tissue slices or tissue homogenates of liver, skeletal muscle, fat skin and blood were conducted to determine whether the uptake of procainamide, lignocaine and pethidine into the hindquarters of sheep was due to distribution or metabolism. Both homogenates and slice preparations of liver showed significant metabolism or uptake, confirming the viability of the preparations. 2. None of the drugs was metabolized in blood and there was minimal uptake of the drugs into the skin. 3. There was metabolism of pethidine in skeletal muscle and substantial uptake of pethidine into fat, indicating that the rapid rate of uptake and prolonged elution of pethidine in the hindquarters was due to both distribution and metabolism. 4. No metabolism of lignocaine in muscle was found, but there was substantial uptake into fat, indicating that the rapid rate of uptake and prolonged elution of lignocaine in the hindquarters was due to its distribution into fat. 5. There was negligible uptake of procainamide into either muscle or fat, presumably due to its relatively low lipophilicity.