TYZEKA
Clinical safety rating: caution
Comprehensive clinical and safety monograph for TYZEKA (TYZEKA).
Telbivudine is a synthetic thymidine nucleoside analogue with activity against hepatitis B virus (HBV). It is phosphorylated intracellularly to the active triphosphate form, which competes with natural thymidine triphosphate for incorporation into viral DNA, causing chain termination and inhibition of HBV DNA polymerase (reverse transcriptase).
| Metabolism | Telbivudine is not significantly metabolized by cytochrome P450 enzymes. It is predominantly excreted unchanged in urine via glomerular filtration and active tubular secretion. No significant metabolites have been identified. |
| Excretion | Renal excretion of unchanged drug accounts for approximately 40% of the administered dose; biliary/fecal excretion accounts for approximately 60%. |
| Half-life | Terminal elimination half-life is approximately 15 hours (range 12-20 hours) in patients with normal renal function; half-life is prolonged in renal impairment, requiring dose adjustment. |
| Protein binding | Approximately 90% bound to human serum albumin. |
| Volume of Distribution | Volume of distribution (Vd/F) is approximately 38 L (0.5 L/kg in a 70 kg adult), indicating extensive extravascular distribution. |
| Bioavailability | Oral bioavailability is approximately 50% (range 40-60%). |
| Onset of Action | Oral administration: time to peak plasma concentration (Tmax) is 1.5-2.5 hours; antiviral effect begins within hours. |
| Duration of Action | Duration of action is approximately 24 hours based on once-daily dosing schedule; sustained viral suppression with consistent trough concentrations. |
| Molecular Weight | 352.36 Da |
600 mg orally once daily
| Dosage form | TABLET |
| Renal impairment | CrCl 30-49 mL/min: 600 mg every 48 hours; CrCl 10-29 mL/min: 600 mg every 72 hours; CrCl <10 mL/min or hemodialysis: 600 mg every 96 hours (administer after dialysis) |
| Liver impairment | No dose adjustment required for mild to moderate hepatic impairment (Child-Pugh A or B). Safety and efficacy not established in severe hepatic impairment (Child-Pugh C). |
| Pediatric use | Approved for children ≥2 years weighing ≥10 kg: 600 mg orally once daily. Safety and efficacy not established in children <2 years. |
| Geriatric use | No specific dose adjustment recommended; use with caution due to age-related renal impairment, and adjust dose based on renal function. |
| 1st trimester | Avoid. Limited human data; animal studies show embryotoxicity. Consider alternatives. |
| 2nd trimester | Use only if clearly needed. No adequate human studies; potential for fetal harm. |
| 3rd trimester | Use only if clearly needed. No adequate human studies; risk of neonatal toxicity. |
Clinical note
Comprehensive clinical and safety monograph for TYZEKA (TYZEKA).
| Placental transfer | Telbivudine crosses the placenta in humans based on cord blood concentrations approximately equal to maternal plasma. |
| Breastfeeding | Excreted into human milk in low amounts; limited data on infant effects. Caution if breastfeeding, especially in neonates. |
| Lactation Rating |
■ FDA Black Box Warning
WARNING: LACTIC ACIDOSIS AND SEVERE HEPATOMEGALY WITH STEATOSIS, including fatal cases, have been reported with the use of nucleoside analogues alone or in combination with antiretrovirals. Additionally, severe acute exacerbations of hepatitis B have been reported in patients who have discontinued anti-hepatitis B therapy, including telbivudine. Hepatic function should be monitored closely in patients who discontinue therapy.
| Serious Effects |
Hypersensitivity to telbivudine or any component of the formulation
| Precautions | Lactic acidosis and severe hepatomegaly with steatosis, Severe acute exacerbation of hepatitis B upon discontinuation, Myopathy and peripheral neuropathy, Renal impairment: dose adjustment required, Pancreatitis, Elevated liver enzymes during therapy |
| Food/Dietary | No known food interactions. Take with or without food. Maintain adequate hydration. Avoid alcohol due to hepatotoxicity. |
Loading safety data…
| L3 (Moderately Safe) |
| Teratogenic Risk | Telbivudine (Tyzeka) is classified as FDA Pregnancy Category B. Animal studies have shown no evidence of embryotoxicity or teratogenicity. There are no adequate and well-controlled studies in pregnant women. Use in first trimester is not associated with increased risk of major birth defects; limited data suggest no fetal harm in second and third trimesters. |
| Fetal Monitoring | Monitor hepatic function, renal function, and lactic acid levels periodically. Assess for signs of pancreatitis and peripheral neuropathy. Fetal monitoring with ultrasound if used in pregnancy; monitor for emergence of HBV resistance. |
| Fertility Effects | Telbivudine has not been shown to impair fertility in animal studies. No human data on fertility effects. Reversible sperm abnormalities not reported; no impact on reproductive organ function. |
| Clinical Pearls | TYZEKA (telbivudine) is a nucleoside analog reverse transcriptase inhibitor for chronic hepatitis B. Monitor LFTs and HBV DNA every 3-6 months. Watch for peripheral neuropathy, especially if combined with interferons. Renal function adjustment required: reduce dose if CrCl <50 mL/min. Avoid in patients with pre-existing myopathy; creatine kinase elevation common. Not first-line due to resistance risk. |
| Patient Advice | Take exactly as prescribed; do not stop without consulting your doctor. · Report any new muscle pain, weakness, or numbness immediately. · Regular blood tests are required to monitor liver function and virus levels. · Use effective contraception during treatment and for 4 weeks after stopping. · Avoid alcohol completely as it can worsen liver damage. · Do not take any new medications, including over-the-counter, without approval. |