Tenvir

Description

Tenofovir disoproxil fumarate is a nucleotide reverse transcriptase inhibitor. Once you take it, your body converts it into tenofovir, which then becomes tenofovir diphosphate. This active form works by blocking the activity of HIV-1 reverse transcriptase, an enzyme crucial for the virus’s replication.

Dosage Information

Tenvir is taken orally and can be consumed with or without food, but it’s important to be consistent (always with or always without food).

• Adults: The typical dose for chronic hepatitis B and HIV infection is 300 mg once daily. For HIV, it’s used in combination with other antiretroviral agents.
• Children:
  • HIV Infection:
    • Under 2 years: Safety and effectiveness haven’t been established.
    • Over 2 years: 8 mg/kg orally once daily, not exceeding 300 mg/day.
  • Hepatitis B Infection:
    • Under 12 years: Safety and effectiveness haven’t been established.
    • Over 12 years and under 35 kg: Safety and effectiveness haven’t been established.
    • Over 12 years and over 35 kg: 300 mg orally once daily.
• Renal Impairment: Dosing needs adjustment for patients with kidney problems:
  • Creatinine Clearance (CrCl) 10-29 ml/min: 300 mg every 72-96 hours.
  • CrCl 30-49 ml/min: 300 mg every 48 hours.
  • Hemodialysis Patients: 300 mg once every 7 days or after a total of 12 hours of dialysis.

Important Considerations

• Contraindications: Do not take Tenvir if you have a known hypersensitivity (allergy) to tenofovir or any of its ingredients.
• Precautions:
  • Use with caution if you have hepatomegaly (enlarged liver) or other risk factors for liver disease.
  • Careful monitoring is needed if you have renal impairment.
  • Pregnancy: Discuss with your doctor if you are pregnant.
  • Lactation: HIV-positive women are advised not to breastfeed.
  • Patient Counseling: This medication can cause dizziness. If you experience this, avoid driving or operating machinery.
• Monitoring: Your doctor will monitor your renal function and serum phosphate levels before starting therapy, then weekly for the first month, and every three months afterward. Hepatic (liver) function will also be monitored for several months after stopping the medication. Before starting treatment for hepatitis B, your HIV status will be determined.

Potential Interactions

• Decreased atazanavir concentration: If you’re taking atazanavir, its levels may decrease unless also taken with ritonavir.
• Increased tenofovir levels: Levels of tenofovir or co-administered drugs may increase if taken with medications eliminated by active tubular secretion.
• Potentially Fatal Interactions (Avoid if possible):
  • Nephrotoxic agents: Concurrent or recent use of drugs that can harm the kidneys (e.g., aminoglycosides, amphotericin B, foscarnet, ganciclovir, pentamidine, vancomycin, cidofovir, or interleukin-2) can significantly increase the risk of renal impairment. If unavoidable, kidney function must be monitored weekly.
  • Didanosine: Concurrent use with didanosine can increase its levels, raising the risk of pancreatitis and peripheral neuropathy, and has been associated with a high treatment failure rate. Avoid concurrent use.

Possible Side Effects

Common side effects (more than 10%) include:

• Asthenia (weakness)
• Diarrhea
• Nausea
• Pain

Less common side effects (1-10%) include:

• Anorexia
• Depression
• Myalgia (muscle pain)
• Peripheral neuropathy (nerve damage)
• Dyspepsia (indigestion)
• Rash
• Headache
• Vomiting
• Flatulence
• Abdominal pain
• Neutropenia (low white blood cell count)
• Increased transaminases (liver enzymes)