Biomaterial Database

Intravenous phenytoin and phenobarbital: anticonvulsant action, brain content, and plasma binding in rat. 1979

I E Leppik, and A L Sherwin

14C-phenytoin or 3H-phenobarbital were given through indwelling jugular catheters to 65 rats. Anticonvulsant activity was tested by the maximal electroshock seizure test and was correlated with brain concentrations of phenytoin or phenobarbital. Free and total plasma drug levels were determined by equilibrium dialysis. The median effective cerebral phenytoin concentration (EC50) was 10.5 microM/kg (95% fiducial limits, 8.2 to 12.4) 3 min after infusion compared with 10.2 microM/kg 30 min after infusion. The EC50 of phenobarbital was 8.2 microM/kg (6.7 to 9.3 microM/kg) 3 min after infusion. Cerebellar concentrations were equivalent to cerebral concentrations for all rats (r = 0.98). Three minutes after infusion, cerebral:plasma free ratio of phenytoin was 3.73 +/- 0.71 (+/- S.D.); the plasma protein bound:free ratio, 3.70 +/- 0.98. For phenobarbital, the cerebral:plasma free ratio was 0.72 +/- 0.10; the plasma protein bound:free ratio, 0.63 +/- 0.12. Since the EC50 values of phenytoin 3 or 30 min after infusion did not differ, onset of anticonvulsant effect clearly occurred as soon as adequate brain concentrations were attained. Phenobarbital was effective 3 min after infusion, and although much higher free plasma levels were necessary, effective brain concentrations were similar to those of phenytoin. Brain content paralleled plasma protein binding, both being high for phenytoin and low for phenobarbital.

UI	MeSH Term	Description	Entries
D007263	Infusions, Parenteral	The administration of liquid medication, nutrient, or other fluid through some other route than the alimentary canal, usually over minutes or hours, either by gravity flow or often by infusion pumping.	Intra-Abdominal Infusions,Intraperitoneal Infusions,Parenteral Infusions,Peritoneal Infusions,Infusion, Intra-Abdominal,Infusion, Intraperitoneal,Infusion, Parenteral,Infusion, Peritoneal,Infusions, Intra-Abdominal,Infusions, Intraperitoneal,Infusions, Peritoneal,Intra Abdominal Infusions,Intra-Abdominal Infusion,Intraperitoneal Infusion,Parenteral Infusion,Peritoneal Infusion
D008297	Male		Males
D010634	Phenobarbital	A barbituric acid derivative that acts as a nonselective central nervous system depressant. It potentiates GAMMA-AMINOBUTYRIC ACID action on GABA-A RECEPTORS, and modulates chloride currents through receptor channels. It also inhibits glutamate induced depolarizations.	Phenemal,Phenobarbitone,Phenylbarbital,Gardenal,Hysteps,Luminal,Phenobarbital Sodium,Phenobarbital, Monosodium Salt,Phenylethylbarbituric Acid,Acid, Phenylethylbarbituric,Monosodium Salt Phenobarbital,Sodium, Phenobarbital
D010672	Phenytoin	An anticonvulsant that is used to treat a wide variety of seizures. It is also an anti-arrhythmic and a muscle relaxant. The mechanism of therapeutic action is not clear, although several cellular actions have been described including effects on ion channels, active transport, and general membrane stabilization. The mechanism of its muscle relaxant effect appears to involve a reduction in the sensitivity of muscle spindles to stretch. Phenytoin has been proposed for several other therapeutic uses, but its use has been limited by its many adverse effects and interactions with other drugs.	Diphenylhydantoin,Fenitoin,Phenhydan,5,5-Diphenylhydantoin,5,5-diphenylimidazolidine-2,4-dione,Antisacer,Difenin,Dihydan,Dilantin,Epamin,Epanutin,Hydantol,Phenytoin Sodium,Sodium Diphenylhydantoinate,Diphenylhydantoinate, Sodium
D011485	Protein Binding	The process in which substances, either endogenous or exogenous, bind to proteins, peptides, enzymes, protein precursors, or allied compounds. Specific protein-binding measures are often used as assays in diagnostic assessments.	Plasma Protein Binding Capacity,Binding, Protein
D001921	Brain	The part of CENTRAL NERVOUS SYSTEM that is contained within the skull (CRANIUM). Arising from the NEURAL TUBE, the embryonic brain is comprised of three major parts including PROSENCEPHALON (the forebrain); MESENCEPHALON (the midbrain); and RHOMBENCEPHALON (the hindbrain). The developed brain consists of CEREBRUM; CEREBELLUM; and other structures in the BRAIN STEM.	Encephalon
D000818	Animals	Unicellular or multicellular, heterotrophic organisms, that have sensation and the power of voluntary movement. Under the older five kingdom paradigm, Animalia was one of the kingdoms. Under the modern three domain model, Animalia represents one of the many groups in the domain EUKARYOTA.	Animal,Metazoa,Animalia
D051381	Rats	The common name for the genus Rattus.	Rattus,Rats, Laboratory,Rats, Norway,Rattus norvegicus,Laboratory Rat,Laboratory Rats,Norway Rat,Norway Rats,Rat,Rat, Laboratory,Rat, Norway,norvegicus, Rattus