Primidone indications

Epilepsy, monotherapy Indicated for conversion to monotherapy in adults with partial seizures who are receiving treatment with carbamazepine, phenytoin, phenobarbital, primidone, or valproate as the single antiepileptic drug (AED). 

Phenobarbital and primidone are quite similar both chemically and pharmacologically, and much of the anticonvulsant activity of primidone may be ascribed to its metabolic conversion to phenobarbital. As would be expected in such a case, the clinical indications for the two compounds are very similar. There is some indication that primidone may be more effective in the treatment of partial seizures with complex symptoms, but the evidence is not compelling. 

The dose-related adverse effects of primidone are similar to those of its metabolite, phenobarbital, except that drowsiness occurs early in treatment and may be prominent if the initial dose is too large. Gradual increments are indicated when starting the drug in either children or adults. 

Primidone is indicated in control of grand mal, psychomotor, or focal epileptic seizures, either alone or with other anticonvulsants. It may control grand mal seizures refractory to other anticonvulsants. Primidone raises electroshock or chemoshock seizure thresholds, or alters seizure patterns. The mechaifism of its antiepileptic action is not known. 

Succinimides are indicated for the monotherapy of absence seizures or with concomitant therapy when additional forms of seizures occur in combination with absence seizures. These drugs are readily absorbed from the gastrointestinal tract and display very low protein binding. The drug interactions for the succinimides are less extensive than with the oxazolidinediones. They may increase plasma phenytoin levels, decrease plasma primidone levels, and either increase or decrease valproate levels, although the changes may not be clinically significant. 

X-ray powder diffraction patterns (7,8) and infrared spectra (see Section 2,1) indicate that primidone may crystallize in at least two different forms. One of these (here designated Form I) usually crystallizes when a solution of primidone in 95 percent ethanol is evaporated at room temperature. The second (here designated Form II) usually forms if primidone... 

Anticonvulsants Anticonvulsants were one of the first groups of drugs for which TDM was indicated. The common anticonvulsants encountered in clinical practice are phenobarbitone, primidone (metabolized to phenobarbitone), phenytoin, carbamazepine, ethosuximide, and valproate. The majority of assays for these drugs are immunoassays these days as 24 h availability of measurements of these drugs has become the general expectation. 

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