Changes

==Pharmacologic Considerations==

==Pharmacologic Considerations==

In man, 60-90% of an oral does of primidone is absorbed from the gastointestinal tract, with serum levels peaking about three hours following administration. Absorption is thought to be similar in animals, but primidone is metabolised once absorbed. Oxidation at carbon 2 results in the formation of phenobarbital, and cleavage at the same site gives PEMA. Primidone, phenobarbital and PEMA all possess anticonvulsant activity, but 85% primidone's activity in dogs is due to the phenobarbital it forms. This is because the potentcy of primidone and PEMA is one-thirtieth that of phenobarbital, and phenobarbital accumulates to the highest concentrations since it is the compound with the longest half-life.  

In man, 60-90% of an oral dose of primidone is absorbed from the gastointestinal tract, with serum levels peaking about three hours after administration. Absorption is thought to be similar in animals, but primidone is metabolised once absorbed. Oxidation at carbon 2 results in the formation of phenobarbital, and cleavage at the same site gives PEMA. Primidone, phenobarbital and PEMA all possess anticonvulsant activity, but 85% of primidone's activity in dogs is due to the phenobarbital it forms. This is because the potentcy of primidone and PEMA is one-thirtieth that of phenobarbital, and phenobarbital has the longest hal-life and so accumulates to the highest concentrations.  

Some vets use primidone continues in patients which are refractory to phenobarbital, even at maximum doses. at the maximum therapeutic drug concentration. The efficacy of primidone in this capacity has not been proven, and mau simply be due to animals receiving primidone metabolising the drug to greater concentrations of phenobarbital that those generated from administration of straight phenobarbital. In most dogs, however, there is no advantage in using primidone over phenobarbital for seizure control, and there are added side effects. Primidone is also more expensive than phenobarbital, but in some countries may be subject to lesser degrees of control and record keeping.

Some vets use primidone in patients which are refractory to phenobarbital at maximum doses. The efficacy of primidone in this capacity has not been proven, and may simply be due to animals receiving primidone metabolising the drug to greater concentrations of phenobarbital than those generated from administration of straight phenobarbital. In most dogs, however, there is no advantage in using primidone over phenobarbital for seizure control, and there are added side effects. Primidone is also more expensive than phenobarbital, but in some countries may be subject to lesser degrees of control and record keeping.

Cats metabolise primidone to phenobarbital to a lesser extent than dogs, so it follows that the drug may be less effective and more toxic. Primidone is not recommended for use in cats.

Cats metabolise primidone to phenobarbital to a lesser extent than dogs, so it follows that the drug may be less effective and more toxic. Primidone is not recommended for use in cats.