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Journal of Dairy Science Dec 1973
Topics: Administration, Oral; Animals; Carbon Radioisotopes; Cattle; Chromatography, Gas; Feces; Female; Lactation; Milk; Phenobarbital; Pregnancy; Rumen; Spectrophotometry, Ultraviolet
PubMed: 4766733
DOI: 10.3168/jds.S0022-0302(73)85408-6 -
American Journal of Veterinary Research May 1987Pharmacokinetics of phenobarbital was examined in 6 mature horses after 12 mg of phenobarbital/kg of body weight was infused over 20 minutes. Biexponential decrease in...
Pharmacokinetics of phenobarbital was examined in 6 mature horses after 12 mg of phenobarbital/kg of body weight was infused over 20 minutes. Biexponential decrease in serum phenobarbital concentrations was observed with a distribution-phase half-life of 0.101 +/- 0.086 hour (mean +/- SD) and a terminal-phase elimination half-life of 18.3 +/- 3.65 hours. The volume of distribution at steady state was 0.803 +/- 0.070 L/kg. Total body clearance of phenobarbital was 30.8 +/- 6.2 ml/h/kg. The high clearance in the horse seems to explain the markedly shorter half-life of phenobarbital in this species. Seemingly, 6.65 mg of phenobarbital/kg as a 20-minute infusion given every 12 hours would provide approximate peaks of 29 micrograms/ml and troughs of 15 micrograms/ml. A loading dose of 12 mg of phenobarbital/kg would be appropriate for this regimen.
Topics: Animals; Female; Horses; Kinetics; Male; Phenobarbital
PubMed: 3592381
DOI: No ID Found -
Pediatric Pharmacology (New York, N.Y.) 1981Phenobarbital was administered to five patients, eight to 20 years of age, by four different administration routes: Intravenous, intramuscular, oral, and rectal. At each...
Phenobarbital was administered to five patients, eight to 20 years of age, by four different administration routes: Intravenous, intramuscular, oral, and rectal. At each administration, extent of bioavailability, elimination rate constant, absorption rate constant, and volume of distribution of phenobarbital were calculated using a one-compartment open model. The results obtained suggest that rectal administration of phenobarbital is more reliable than intramuscular or oral administration of the drug for rapid treatment in children.
Topics: Adolescent; Adult; Biological Availability; Child; Humans; Intestinal Absorption; Kinetics; Phenobarbital; Rectum; Suppositories; Time Factors
PubMed: 7346746
DOI: No ID Found -
Pediatrics Oct 1977Blood levels of phenobarbital were determined after a single oral or intramuscular (IM) dose in children in the hospital after febrile convulsions. At a dose of 15...
Blood levels of phenobarbital were determined after a single oral or intramuscular (IM) dose in children in the hospital after febrile convulsions. At a dose of 15 mg/kg, both the oral and IM routes gave therapeutic blood levels within 90 minutes. Absorption from the IM route before 90 minutes was inconsistent and would be unlikely to arrest an established convulsion within a critical time period. For use as a drug to prevent convulsions, oral phenobarbital at 15 mg/kg deserves further study.
Topics: Child, Preschool; Humans; Infant; Injections, Intramuscular; Phenobarbital; Seizures, Febrile
PubMed: 263268
DOI: No ID Found -
Pediatrics May 1989The optimal serum concentration of phenobarbital in newborns and its safety at high doses are not well established. The dose response relationship of rapid sequential... (Comparative Study)
Comparative Study
The optimal serum concentration of phenobarbital in newborns and its safety at high doses are not well established. The dose response relationship of rapid sequential phenobarbital loading in the newborn was examined and the efficacy of high-dose monotherapy was compared with the addition of a second anticonvulsant for persistent seizure activity. A single loading dose of phenobarbital 15 to 20 mg/kg was initially administered to 120 newborns. Nonresponders received sequential bolus doses of 5 to 10 mg/kg until seizures ceased or a serum concentration of 40 micrograms/mL was obtained. Infants with refractory seizures received additional phenobarbital to a maximum serum concentration of 100 micrograms/mL. The seizures of 48 babies (40%) were controlled after initial loading and 37 of the remaining 72 subjects (51%) responded at serum concentrations of as great as 40 micrograms/mL. The seizures of only seven subjects were controlled at greater concentrations. A second anticonvulsant controlled seizures in 13 of the 28 subjects (46%) whose seizures were refractory to phenobarbital. A gestational age of less than 32 weeks was associated with a significantly better response to phenobarbital. Serum phenobarbital concentrations greater than 50 micrograms/mL produced only occasional feeding difficulty and sedation. It was concluded that sequentially administered IV phenobarbital controls seizures in both term and preterm newborns (77%). This therapeutic effect is dose dependent but plateaus at a serum concentration of 40 micrograms/mL. At greater serum concentrations, unresponsive patients should receive a second antiepileptic agent.
Topics: Dose-Response Relationship, Drug; Gestational Age; Humans; Infant, Newborn; Lorazepam; Phenobarbital; Phenytoin; Seizures
PubMed: 2717283
DOI: No ID Found -
Canadian Journal of Physiology and... Jun 1973
Topics: Alcoholic Intoxication; Animals; Brain; Carbon Isotopes; Chromatography, Paper; Drug Interactions; Ethanol; Feces; Humans; Liver; Male; Phenobarbital; Rats; Time Factors
PubMed: 4737977
DOI: 10.1139/y73-067 -
Journal of Pharmaceutical Sciences Apr 1984A three-way crossover study was conducted with 24 healthy male volunteers to determine the relative bioavailability of four different 100-mg phenobarbital tablets...
A three-way crossover study was conducted with 24 healthy male volunteers to determine the relative bioavailability of four different 100-mg phenobarbital tablets compared with a reference elixir. Each subject received two of the tablets and the elixir at 30-d intervals. Blood samples were collected daily for 19 d after each dose. Plasma phenobarbital concentrations achieved with the five dosage forms differed by less than 20% within 2-3 h after dosing. The extent of absorption for all dosage forms, as determined from area under the plasma concentration-time profiles, were within 10% of each other. The peak plasma concentration was the greatest and the time to peak concentration was the shortest for the elixir. One of the tablets exhibited a time to peak concentration of 8.6 h, which was significantly longer than any of the other dosage forms. The time to peak concentration correlated with the percent of drug dissolved in 60 min, as determined in 0.1 M HCl, using the USP XX paddle method at 50 rpm.
Topics: Adult; Biological Availability; Humans; Intestinal Absorption; Male; Phenobarbital; Solubility; Solutions; Tablets; Time Factors
PubMed: 6726633
DOI: 10.1002/jps.2600730414 -
Forensic Science International Jan 1995Phenobarbital analysis was performed in vertex hair of patients by gas chromatography mass spectrometry (GC/MS). After washing with dichloromethane, about 250 mg were...
Phenobarbital analysis was performed in vertex hair of patients by gas chromatography mass spectrometry (GC/MS). After washing with dichloromethane, about 250 mg were ground to dust in a ball mill. A 50-mg sample was stirred mechanically for 10 min with 3 ml of NH4Cl/HCl buffer (pH 2.0) containing phenobarbital D5. A solid phase extraction was performed (extrelut Merck) and elution was achieved with chloroform/isopropanol/n-heptane (50:17:33; v/v). A full scan (40-240 uma) acquisition was realized by GC/MS with an ion trap (ITD 700 Finnigan) using a DB5-MS chromatographic column. Quantification was achieved by integrating dominants ions (phenobarbital, 204; phenobarbital D5, 209). Compared to serum, hair concentrates phenobarbital during anti-epileptic therapy (average value 36.4 ng/mg, n = 40 vs. 18.7 mg/l, n = 23). A group correlation exists between phenobarbital in hair and phenobarbital in serum, and between phenobarbital in hair and clinic observation in some typical cases. Phenobarbital in hair yields good information over a long period, especially when blood collection has not been made, when clinical disorders are observed on long-term therapeutic observance.
Topics: Adult; Drug Monitoring; Epilepsy; Female; Gas Chromatography-Mass Spectrometry; Hair; Humans; Male; Middle Aged; Phenobarbital
PubMed: 7860031
DOI: 10.1016/0379-0738(94)01619-g -
Journal of Clinical Pharmacology 1978The absorption of phenobarbital was compared in healthy adult subjects after oral and intramuscular therapeutic doses. Serum levels of phenobarbital were determined for... (Comparative Study)
Comparative Study
The absorption of phenobarbital was compared in healthy adult subjects after oral and intramuscular therapeutic doses. Serum levels of phenobarbital were determined for 21 days after dosing by means of radioimmunoassay. Serum levels were similar from both dosage routes, with peak levels occurring at 1-3 hours after dosing and then declining slowly with an elimination half-life of about 90 hours. The overall efficiency of phenobarbital absorption from intramuscular doses was approximately 80 per cent of that from equivalent oral doses. Except in cases where oral dosing is not appropriate, there is no clinical advantage in giving phenobarbital intramuscularly to adult patients.
Topics: Administration, Oral; Adult; Biological Availability; Humans; Injections, Intramuscular; Kinetics; Male; Phenobarbital
PubMed: 624773
DOI: 10.1002/j.1552-4604.1978.tb02428.x -
Neurology Dec 1984A 2-year-old child with known neurologic impairment developed a dyskinesia soon after starting phenobarbital therapy for seizures. Known causes of movement disorders...
A 2-year-old child with known neurologic impairment developed a dyskinesia soon after starting phenobarbital therapy for seizures. Known causes of movement disorders were eliminated after evaluation. On repeat challenge with phenobarbital, the dyskinesia recurred. Phenobarbital should be added to the list of anticonvulsant drugs that can cause movement disorders.
Topics: Child, Preschool; Dyskinesia, Drug-Induced; Humans; Male; Phenobarbital; Seizures
PubMed: 6504332
DOI: 10.1212/wnl.34.12.1600