lamivudine/tenofovir disoproxil fumarate

General

Pronunciation:
la-mi-vyoo-deen/te-noe-fo-veer dye-soe-prox-il fue-ma-rate

Trade Name(s)

  • Cimduo

Ther. Class.
antiretrovirals

Pharm. Class.
nucleoside reverse transcriptase inhibitors

Indications

Treatment of HIV infection (with other antiretroviral agents).

Action

  • Lamivudine–After intracellular conversion to its active form (lamivudine-5-triphosphate), inhibits viral DNA synthesis by inhibiting the enzyme HIV reverse transcriptase.
  • Tenofovir–Phosphorylated intracellularly where it inhibits HIV reverse transcriptase resulting in disruption of DNA synthesis.

Therapeutic Effect(s):

Slowed progression of HIV infection and decreased occurrence of sequelae.

Pharmacokinetics

Absorption: Lamivudine–Well absorbed after oral administration (86% in adults, 66% in infants and children); tenofovir–Tenofovir disoproxil fumarate is a prodrug, which is split into tenofovir, the active component; absorption enhanced by food.

Distribution: Lamivudine–Distributes into the extravascular space; some penetration into CSF; tenofovir–Distributes into the extravascular space.

Metabolism and Excretion: Lamivudine–Mostly excreted unchanged in urine; <5% metabolized by the liver; tenofovir–70–80% excreted unchanged in urine by glomerular filtration and active tubular secretion.

Half-life: Lamivudine––5–7 hrtenofovir–17 hr.

TIME/ACTION PROFILE (blood levels)

ROUTEONSETPEAKDURATION
lamivudine POunknown 0.9 hr12 hr
tenofovir POunknown2 hr†24 hr
†When taken with food.

Contraindication/Precautions

Contraindicated in:

  • Hypersensitivity;
  • Coinfection with hepatitis B virus (HBV) (hepatitis may recur after discontinuation of lamivudine or tenofovir) (lamivudine dosage not appropriate for patients co-infected with HBV);
  • CCr <50 mL/min
  • Concurrent or recent use of nephrotoxic medications
  • Concurrent use with ribavirin and/or interferon alfa (↑ risk of hepatic decompensation)
  • Lactation: Breastfeeding not recommended for HIV positive mothers.

Use Cautiously in:

  • History of pathologic fractures/osteoporosis/bone loss;
  • Geri: Choose dose carefully, considering concurrent disease states, drug therapy, and age-related ↓ in hepatic and renal function;
  • OB: Use in pregnancy only if maternal benefit outweighs fetal risk;
  • Pedi: Children with a history of or significant risk factors for pancreatitis;
  • Pedi: Children <35 kg (safety and effectiveness not established).

Adverse Reactions/Side Effects

CNS: depression, headache, anxiety, dizziness, insomnia

Derm: rash, urticaria

F and E: LACTIC ACIDOSIS

GI: HEPATOMEGALY WITH STEATOSIS, PANCREATITIS (↑ IN PEDIATRIC PATIENTS), diarrhea, abdominal pain, dyspepsia, ↑ liver enzymes, nausea, vomiting

GU: ACUTE RENAL FAILURE/FANCONI SYNDROME, hematuria

Hemat: neutropenia

Metabolic: hypercholesterolemia, ↑ creatine kinase, fat redistribution

MS: arthralgia, ↓ bone mineral density, muscle weakness, myalgia, osteomalacia

Neuro: peripheral neuropathy

Misc: fever, immune reconstitution syndrome,

* CAPITALS indicate life-threatening.
Underline indicate most frequent.

Interactions

Drug-Drug

  • Nephrotoxic drugs, including acyclovir, aminoglycosides, cidofovir, ganciclovir, NSAIDs, valacyclovir, or valgancyclovir may ↑ risk of nephrotoxicity; avoid recent or concurrent use.
  • May ↑ risk of hepatic decompensation with ribavirin or interferon alfa; avoid concurrent use.
  • Ledipasvir/sofosbuvir and sofosbuvir/velpatasvir may ↑ tenofovir levels.
  • Trimethoprim/sulfamethoxazole may ↑ lamivudine levels.
  • Medications containing sorbitol may ↓ lamivudine levels.

Route/Dosage

PO (Adults and Children) ≥35 kg) 1 tablet once daily.

Availability

Tablets: lamivudine 300 mg/tenofovir disoproxil fumarate 300 mg

Assessment

  • Monitor for change in severity of HIV symptoms and for symptoms of opportunistic infection before and during therapy.
  • Monitor bone mineral density in patients who have a history of pathologic bone fracture or are at risk for osteoporosis or bone loss. Persistent or worsening bone pain, pain in extremities, fractures and/or muscular pain or weakness may be manifestations of proximal renal tubulopathy.

Lab Test Considerations: Monitor viral load and CD4 count before and routinely during therapy to determine response.

  • Test for hepatitis B before starting therapy. Monitor liver function tests and hepatitis B virus levels during and following therapy. If therapy is discontinued, may cause severe exacerbation of hepatitis B. May cause ↑ AST, ALT, alkaline phosphatase, creatine kinase, amylase, and triglyceride concentrations. Lactic acidosis may occur with hepatic toxicity causing hepatic steatosis; may be fatal, especially in women.
  • Assess serum creatinine, serum phosphorus, CCr, urine glucose, and urine protein before starting and periodically during therapy. Calculate CCr prior to and periodically during therapy and when clinically indicated. In patients at risk of renal dysfunction, assess CCr, serum phosphorus, urine glucose, and urine protein prior to and periodically during therapy. Persistent or worsening bone pain, pain in extremities, fractures and/or muscular pain or weakness may be manifestations of proximal renal tubulopathy.
  • Monitor serum phosphate periodically during therapy in patients at risk for renal impairment. May cause hypophosphatemia in patients with renal impairment.
  • May cause hyperglycemia and glucosuria.

Potential Diagnoses

Implementation

  • PO Administer once daily with or without food.

Patient/Family Teaching

  • Instruct patient on the importance of taking lamivudine/tenofovir as directed, even if feeling better. Do not take more than prescribed amount and do not stop taking without consulting health care professional. Discontinuing therapy may lead to severe exacerbations. Advise patient to make sure they have enough medication to not run out; the virus may increase and may become harder to treat. Take missed doses as soon as remembered unless almost time for next dose; do not double doses. Caution patient not to share or trade this medication with others. Advise patient to read Patient Teaching before starting and with each Rx refill in case of changes.
  • Caution patient to avoid crowds and persons with known infections.
  • Inform patient that lamivudine/tenofovir does not cure AIDS and does not reduce the risk of transmission of HIV to others through sexual contact or blood contamination. Caution patient to use a condom and avoid sharing needles or donating blood to prevent spreading HIV to others.
  • Advise patient to notify health care professional immediately if symptoms of lactic acidosis (tired; nausea; vomiting; unusual or unexpected stomach discomfort; trouble breathing; feeling cold, dizzy, lightheaded; fast or irregular heartbeat; weakness), pancreatitis, or signs of immune reconstitution syndrome (signs and symptoms of an infection) occur.
  • Instruct patient to notify health care professional of all Rx or OTC medications, vitamins, or herbal products being taken and consult health care professional before taking any new medications.
  • Inform patient that changes in body fat distribution (increased fat in upper back and neck, breast, and trunk, and loss of fat from legs, arms, and face) may occur, but may not be related to drug therapy.
  • Rep: Advise patient taking oral contraceptives to use a nonhormonal method of birth control during lamivudine/tenofovir therapy. If pregnancy is suspected notify health care professional promptly. Encourage pregnant women to enroll in the Antiretroviral Pregnancy Registry by calling 1-800-258-4263. Advise female patient to avoid breast feeding during therapy.
  • Emphasize the importance of regular exams to monitor for side effects.

Evaluation/Desired Outcomes

Decreased incidence of opportunistic infection and slowed progression of HIV infection.

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