intravenous (iv) administration

The "absorption" phase is the time it takes to inject the drug. Usually iv injections are made quickly so that the plasma concentration reaches an almost instantaneous peak and rapidly declines as the drug is distributed away to other tissues. However, intravenous injections can be made with an infusion pump so that the rate of "absorption" can be directly controlled. This is usually only necessary during anaesthesia or intensive care where potentially dangerous drugs are given to sick animals.

Intravenous injections are usually only used where the drug has to act rapidly (anaesthetics and sedatives), which have to be given in large volumes (fluids) or which are irritant (parenteral nutrition solutions).

Any superficial vein can be used: in dogs and cats the cephalic vein is usually used, although the lateral (dogs) or medial (cats) saphenous vein is also used. In cattle, sheep and horses, the jugular vein is used. In pigs and rabbits, the marginal ear vein is used. In animals in shock, where drugs have to be given into collapsed veins, it is sometimes necessary to cut down onto the vein to place an iv catheter.

cutdown on lateral saphenous vein movie (6.7MB)

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