Reference Values

Reporting limit determined each analysis.

Plasma concentrations of 2-3 mcg/mL produce sedation and plasma concentrations of 25 mcg/mL produce sleep in most patients. Plasma concentrations of greater than 30 mcg/mL may produce coma and plasma concentrations in excess of 50 mcg/mL are potentially lethal.

A single oral 100 mcg dose resulted in a mean peak blood concentration of 2.1 mcg/mL (range, 1.7-2.6 mcg/mL) at 2 hours, with a decline to 1.5 mcg/mL (range, 1.3-1.7 mcg/mL) by 24 hours. Potentially toxic at plasma concentrations greater than 10 mcg/mL.

Peak serum concentrations of 1.2-3.1 mcg/mL were produced 0.5-2.0 hours after a 100 mg oral dose and peak serum concentration of 3 mcg/mL were produced 6 min. following a 100 mg IV dose. Potentially toxic at blood concentrations greater than 10 mcg/mL.

A 3.3 mg/kg oral dose (approx. 230 mg/70 kg) produced a mean peak blood concentration of 2.0 mcg/mL (range, 1.8-2.2 mcg/mL) at 3 hours, diminishing to 1.3 mcg/mL by 20 hours and 0.8 mcg/mL by 40 hours. Potentially toxic at blood concentrations greater than 8 mcg/mL.

Recommended serum concentration range during anticonvulsant therapy with primidone: 10-40 mcg/mL.