Phenobarbital characteristics

In rabbits under light amytal anesthesia, chlordan has no direcr effect on the blood pressure, but produces a type of respiration having many characteristics in common with Cheyne-Stokes type. The generalized tremors, opisthotonus, tonic and clonic convulsions, produced by chlordan were decreased or abolished and respiration restored to normal by suitable injections of the sodium salts of amytal, phenobarbital, and pentothal. The LD60 of chlordan, which was about 20 mg. per kg. on intravenous administration to intact rabbits, was increased to about 60 mg. per kg. through the antidotal action of the barbiturates. An unidentified chlorine-containing degradation product with acidic properties was recovered from the urine of rabbits treated with chlordan. Approximately one third of its chlorine content was set free on hydrolysis at 100° C. with sodium hydroxide in either absolute alcohol or in water. 

The effects of chlordan on the blood pressure and respiration of rabbits under sodium pentothal, in general, were characteristic of those obtained under sodium amytal and sodium phenobarbital, with some variation in intensity and length of duration. 

T. L. Keimig and L. B. McGown, Micellar modification of the spectral, intensity and lifetime characteristics of fluorescein-labeled phenobarbital, Talanta 33, 653-656 (1986). 

Phenobarbital has selective antiseizure activity at low doses and has a long half-life suitable for maintenance treatment in seizure disorders (for characteristics of barbiturates, see sedative-hypnotics). Clonazepam is usually a backup drug in absence and myoclonic seizures it causes marked sedation at anticonvulsant doses. IV lorazepam and diazepam are both used in status epilepticus. 

The stability of the dissolution characteristics of dosage forms during storage can be affected by formulation components and processing. A phenobarbital tablet containing... 

Mephobarbital is indicated for use as a sedative for the relief of anxiety, tension, and apprehension, and as an anticonvulsant for the treatment of grand mal (400 to 600 mg/ day) and petit mal epilepsies (6 to 12 mg/kg p.o./day). Mephobarbital, which is more Upid soluble than phenobarbital, becomes metabolized to phenobarbital. The pharmacologic characteristics of mephobarbital are similar to those of phenobarbital, and it is therefore used as an alternate drug. It has been reported that mephobarbital causes less sedation and hypersensitivity reactions than phenobarbital. Similar to phenobarbital, mephobarbital inhibits posttetanic potentiation and especially raises the seizme threshold. The... 

Barbiturates as a class of drugs mostly possess sedative and hypnotic properties. Surprisingly only a few of them really show anticonvulsant characteristics. Among the most common barbiturates generally employed as anticonvulsants in clinical use are namely phenobarbital, mephobarbital and methabarbital (discussed in the chapter on Sedatives and Hypnotics ) of which phenobarbital is the drug of choice and is used virtually in all the three types of epileptic seizures viz., grand mal, petit mal and psychomotor. 

By virtue of its inherent liver-enzyme-inducing characteristic phenobarbital helps in enhancing the metabolism of such drugs that are usually metabolized by the microsomal enzymes. 

The structural characteristics of individual PCB congeners influence their induction of various P450 activities. In mammals, PCB congeners have been characterized as 3-methylcholanthrene-type inducers, phenobarbital-type inducers, or mixed-type inducers of both. AHH and EROD activities (which are preferentially catalyzed by the P450IA gene subfamily) have been induced by planar PCBs in fish and mammals and by some mono- and di-ortho analogs of planar PCBs in mammals. The mechanism of toxic action of planar and mono-ortho planar PCBs is linked to an interaction with the 2,3,7,8-TCDD (or Ah) receptor protein. But this mechanism does not account for all observed PCB toxici-ties. Toxic responses uiuelated to Ah receptor effects have been reported of PCBs 4, 28, 31, 49, 52, 84, 95, 110, 136, and 153. For example, PCB 153 is less cytotoxic than PCB 169... 

Metabolism The metabolic consequences of enzyme induction, which is characteristic of several antiepileptic drugs (phenytoin, carbamazepine, and phenobarbital), have been reviewed [72 ]. 

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