title: Griseofulvin---phenobarbital interaction: a formulation-dependent phenomenon.
abstract: The reported interaction of griseofulvin with phenobarbital was studied in the rat following oral administration of different dosage forms. A single oral dose of 15 mg of phenobarbital/kg 24 hr prior to the oral administration of a suspension of 100 mg og griseofulvin/kg in 0.5% polysorbate 80 significantly reduced plasma griseofulvin levels. An increase in the concentration of polysorbate 80 to 2% reduced the extent of the interaction from 50 to 32%. Phenobarbital did not influence plasma griseofulvin levels when griseofulvin was given in either 70% polyethylene glycol 300 (suspensions of 20 or 100 mg/kg) or 100% polyethylene glycol 600 (solution of 50 mg/kg). It is concluded that the observed interaction is formulation dependent and is a result of diminished dissolution and, consequently, reduced absorption of griseofulvin.
mesh_terms: D000818:Animals; D004347:Drug Interactions; D006118:Griseofulvin / Q000008:administration & dosage / Q000378:metabolism*; D007408:Intestinal Absorption / Q000187:drug effects*; D008297:Male; D010316:Particle Size; D010634:Phenobarbital / Q000494:pharmacology*; D011092:Polyethylene Glycols; D011136:Polysorbates; D051381:Rats; D012995:Solubility; D012996:Solutions; D013535:Suspensions
chemical_list: D011136:Polysorbates; D012996:Solutions; D013535:Suspensions; D006118:Griseofulvin; D011092:Polyethylene Glycols; D010634:Phenobarbital