Specimen Information

Type

Gray top (fluoride/oxalate), green top (sodium heparin), or lavender top (EDTA) tube, PLASMA

Volume

4.0 ml

Transport Info

Centrifuge and immediately transfer plasma to separate plastic tube
Refrigerated

Fasting Required?

False

Clinical Significance

Amobarbital (amylobarbitone, Amytal) is a barbiturate derivative of inter-mediate duration of action first prepared in 1924. The compound is available as either the sodium salt or the free acid in oral dosage forms of 15-200 mg for use as a sedative or hypnotic, and in ampules of 65-500 mg for intravenous or intramuscular injection for the control of seizures. It is also found in combination with other drugs such as secobarbital and ephedrine. Butalbital (allylbarbital, allylbarbitone, itobarbital, 5-allyl-5-isobutylbarbituric acid, Sandoptal) is a short-acting barbiturate closely related to talbutal and less closely to aprobarbital and secobarbital. It is found in combination with other drugs such as acetaminophen, aspirin, caffeine, codeine, and phenacetin. These "analgesic-sedative" mixtures may contain from 30-50 mg of butalbital and are intended for oral administration. Pentobarbital (pentobarbitone, Nembutal) is a short-acting barbiturate derivative first prepared in 1930. The drug is available alone and in combination with other agents in amounts of 15-200 mg for oral, intramuscular, or rectal administration. It is supplied as the racemic mixture in the form of both the free acid and the sodium salt, the latter being strongly alkaline in aqueous solution. Phenobarbital has been widely prescribed for the treatment of epilepsy, particularly for controlling focal motor or sensory and grand mal seizures, since the discovery of phenobarbital by Hauptmann in 1912. After oral doses of 2 to 3 mg/kg, phenobarbital is almost completely absorbed with peak levels achieved by 12 to 18 hours. Phenobarbital in circulation is approximately 40 to 50 percent bound to plasma protein with a relatively low association constant. The major metabolic pathway of phenobarbital is hydroxylation of the phenyl ring to parahydroxy phenobarbital, an agent devoid of hypnotic activity, which is then excreted in the urine in equal amounts of the free form and the conjugated form with glucuronic acid. The antiepileptic properties of phenobarbital have not yet been explained by a specific mechanism of action. Principally, phenobarbital diminishes the excitability of neurons and reduces excitatory postsynaptic potentials. Secobarbital (quinalbarbitone, Seconal) is a barbiturate derivative of short duration of action first prepared in 1934. It is available in amounts of 8-250 mg alone or in combination with other drugs for use as either a sedative or hypnotic. Both the free acid and sodium salt are utilized and may be administered rectally, orally, or by intravenous and intramuscular injection.