Drug Criteria & Outcomes: Telbivudine Formulary Evaluation
Drug Criteria & Outcomes
Telbivudine Formulary Evaluation
By James M. Davis, Pharm. D. candidate Auburn (AL) University, Harrison School of Pharmacy
[Editor's note: This is part one of a two-part forumulary evaluation of telbivudine. Please see the conclusion of this evaluation in the next issue of Drug Criteria & Outcomes]
Description:
Tyzeka™ (telbivudine): is a synthetic thymidine nucleoside analogue
Baraclude™ (entecavir): is a synthetic guanosine nucleoside analogue
Mechanism of Action:
Tyzeka™ (telbivudine):
The thymidine moiety of telbivudine is phosphorylated by cellular kinases to active form. This triphosphate form is then capable of being incorporated into the viral DNA of HBV where inhibition of reverse transcriptase results in DNA chain termination of HBV.
Baraclude™ (entecavir):
The guanosine portion of entecavir is phosphorylated by cellular kinases to active form where the triphosphate form can inhibit HBV replication by three mechanisms base priming, reverse transcription of the negative strand of mRNA, and inhibition of transcription of the positive strand of mRNA.
Pharmacokinetics:
Tyzeka™ (telbivudine):
Absorption: Exact absorption data is not completely known; however, dose dependent increases in AUC and Cmax have been observed and food intake with dose does not appear to effect absorption.
Distribution: data not currently available
Metabolism: data not currently available
Elimination: primarily renal excretion properties, but extent of significance is currently unknown. T1/2 is 31.5 hours.
Baraclude™ (entecavir):
Absorption: Tablet formulation is equivalent to the oral solution in terms of absorption and can be used interchangeably Food delays absorption and can decrease AUC by up to 20%.
Distribution: entecavir is 13% plasma protein bound, and extensively disturbed to tissue with volume of distribution estimated to be greater than total amount of body water.
Metabolism: unknown; small amounts of glucuronide and sulfate metabolites have been found in kinetics studies.
Elimination: entecavir primarily undergoes renal excretion (63 to 72%) via a dose independent mechanism. Glomerular filtration and tubular secretion are the main routes that excrete entecavir unchanged in the urine resulting in a t1/2 of 128 to 149 hours.
Indications:
Tyzeka™ (telbivudine): is indicated for the treatment of chronic HBV in adult patients with either HBeAg positive or negative, with or without evidence of active disease (elevated liver enzymes and/or increased levels HBV DNA).
Baraclude™ (entecavir): is indicated for the treatment of chronic HBV in adult patients with either HBeAg positive or negative, with or without evidence of active disease (elevated liver enzymes and/or increased levels HBV DNA).
The thymidine moiety of telbivudine is phosphorylated by cellular kinases to active form. This triphosphate form is then capable of being incorporated into the viral DNA of HBV where inhibition of reverse transcriptase results in DNA chain termination of HBV.Subscribe Now for Access
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