Determination of LD50 of Phenobarbital Lab # 6

Outline Phenobarbital: MOA, SE LD 50 Determination of phenobarbital LD50

Phenobarbital Barbiturates group Antiepileptic Sedative-hypnotic

MOA Potentiates the synaptic inhibition through its action on GABA A receptors

SE Sedation Megaloblastic anemia Hypersensitivity reactions Osteomalacia In overdose, it causes coma and respiratory & circulatory failure

LD 50 The median lethal dose that kills 50% of animal population

Determination of LD50 of Phenobarbital Drugs: –Phenobarbital (2%) Instruments: –Cages. –1 ml syringes Animals: 48 mice

LD 50 Calculation Graphical method Arithmetical method (Karber’s method)

Graphical method GroupDose mg/kg Log doseDead% DeadCorrected % Probit Correction formulas: For the 0% dead=100(0.25/n). For the 100% dead=100 [(n-0.25)/n] where n= number of animals in each group

Graphical method LOG DOSE Probit

Karber’s Method GroupDose (mg/kg)Dose difference (mg/kg) = a DeadMean b Product a*b T= LD 50 = 330 – (585/8) = mg/kg