tenofovir disoproxil

CLINICAL USE

Nucleoside reverse transcriptase inhibitor:Treatment of HIV in combination with other antiretroviral drugsTreatment of hepatitis B in compensated liver disease

DOSE IN NORMAL RENAL FUNCTION

245 mg once daily

PHARMACOKINETICS

Molecular weight :635.5 (as disoproxil fumarate)

%Protein binding :0.7–7.2

%Excreted unchanged in urine : IV: 70–80; Oral: 32

Volume of distribution (L/kg) :0.8

half-life – normal/ESRD (hrs) :12–18/Increased

DOSE IN RENAL IMPAIRMENT

GFR (mL/MIN)

30–50 245 mg every 48 hours10–30 245 mg every 72–96 hours

<10 : 245 mg every 7 days

DOSE IN PATIENTS UNDERGOING RENAL REPLACEMENT THERAPIES

CAPD :Unknown dialysability. Dose as in GFR <10 mL/min

HD :Dialysed. Dose as in GFR

<10 : mL/min

HDF/high flux :Dialysed. Dose as in GFR

<10 : mL/min

CAV/VVHD :Dialysed. Dose as in GFR=10–30 mL/min

IMPORTANT DRUG INTERACTIONS

Potentially hazardous interactions with other drugs

Antivirals: reduces concentration of atazanavir; concentration of both drugs may be increased with cidofovir; increased didanosine concentration resulting in increased toxicity (e.g. pancreatitis and lactic acidosis) – avoid concomitant use; concentration increased by lopinavir and atazanavir; monitor renal function with adefovirCo-administration with other drugs that are actively secreted via the tubular anionic transporter, e.g. cidofovir – increased concentrations of both drugs

ADMINISTRATION

Reconstition

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Route

Oral

Rate of Administration

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Comments

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OTHER INFORMATION

Lactic acidosis, sometimes fatal, and usually associated with severe hepatomegaly and steatosis, has been reported in patients receiving nucleoside reverse transcriptase inhibitorsFollowing a single 300 mg dose of tenofovir, subjects with a calculated creatinine clearance <50 mL/min, and those with ERF requiring dialysis, had substantial reductions in renal elimination of tenofovir, resulting in high systemic exposures necessitating an adjustment in doseA 4 hour high-flux haemodialysis session was found to remove 10% of tenofovir from plasmaRenal impairment, which may include hypophosphataemia, has been reported with the use of tenofovir. The majority of these cases occurred in patients with underlying systemic or renal disease, or in patients taking nephrotoxic agents – monitor creatinine clearance and phosphate levels

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