Bioequivalence and Bioavailability Forum

Primidone is absorbed rapidly from the gastrointestinal tract, peak plasma levels being attained approximately 3 hours after ingestion. Primidone is well distributed in all organs and tissues: it crosses the blood-brain and placental barriers and is excreted in breast milk. The pharmacokinetics of primidone are complex because of biotransformation into two metabolites, phenobarbitone and phenylethylmalonamide, that have anticonvulsant activity and complex pharmacokinetic properties.

It is good to analyze the Parent and both metabolites (as they are pharmcologically active).
90% CI date for parent and metabolite data is supportive.

Also look into the safety aspect of drug (whether this product is NTI drug?)
Accordingly study design should be done.

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Edit: Full quote removed. Please delete everything from the text of the original poster which is not necessary in understanding your answer; see also this post! [Ohlbe]