Tenofovir DisoproxilTenofovir Disoproxil Fumarate

About Tenofovir Disoproxil

Tenofovir disoproxil fumarate is a nucleotide reverse transcriptase inhibitor: inside cells it becomes tenofovir, which blocks the enzyme that HIV and the hepatitis B virus use to copy themselves. The label approves it, in combination with other antiretroviral medicines, for HIV-1 infection in adults and children 2 and older who weigh at least 10 kg, and on its own for chronic hepatitis B in the same age and weight range. Adults and children weighing 35 kg or more take one 300 mg tablet once a day, with or without food. Smaller children take 150 mg, 200 mg or 250 mg tablets by weight, or the oral powder, measured in scoops and mixed into soft food. When kidney function is reduced the 300 mg dose is spaced out, every 48 hours or every 72 to 96 hours depending on the creatinine clearance, and once a week after dialysis.

The boxed warning is about hepatitis B: severe flares of hepatitis have occurred in people with hepatitis B who stopped the drug, so liver function is checked closely for at least several months after stopping, and treatment may need to be restarted. Everyone is tested for hepatitis B before or when starting, and anyone treated for hepatitis B is offered an HIV test first, because using tenofovir alone in undiagnosed HIV breeds resistance. There are no contraindications, but the label warns of new or worsening kidney impairment, including Fanconi syndrome, so kidney function is assessed before and during treatment and other kidney-harming drugs, such as high-dose or multiple NSAIDs, are avoided; of bone loss and, with kidney tubule damage, softening of the bones; of lactic acidosis and severe liver enlargement with fat; and of immune reconstitution syndrome when HIV treatment starts. Rash, diarrhea, nausea, headache, pain, depression and weakness were the most common side effects in HIV trials, and nausea in hepatitis B.

What is distinctive is the interaction list and the family of tenofovir products. Tenofovir raises didanosine levels, lowers atazanavir levels unless ritonavir is added, and its own level rises with ritonavir-boosted protease inhibitors and with the hepatitis C combinations sofosbuvir and velpatasvir or ledipasvir and sofosbuvir, so these pairings are monitored. Acyclovir, valganciclovir and aminoglycoside antibiotics can also raise its level. Tenofovir disoproxil is one ingredient of several combination tablets, so a prescription is checked to make sure it is not doubled up. The Antiretroviral Pregnancy Registry has found no increase in the overall risk of major birth defects with first trimester exposure, and mothers treated for HIV are told not to breastfeed. Tenofovir disoproxil is not a controlled substance.

Taking Tenofovir Disoproxil

How to take it

Take one tablet by mouth once a day, with or without food, at about the same time each day, together with the other HIV medicines the prescriber ordered. Do not stop without talking to the prescriber, because hepatitis B can flare after the drug is stopped. The oral powder is measured with its scoop, mixed into soft food, not liquid, and eaten right away.

If you miss a dose

Take it as soon as you remember, unless it is almost time for the next dose; then skip the missed dose. Do not take a double dose, and tell the prescriber if you miss doses often.

Storage

In the original container at room temperature, away from heat and moisture (not in the bathroom), out of reach of children.

Interactions to know about

Didanosine levels rise and its dose is lowered; atazanavir needs ritonavir with it; ritonavir-boosted protease inhibitors, sofosbuvir with velpatasvir, and ledipasvir with sofosbuvir raise tenofovir levels and call for monitoring. Avoid other kidney-harming drugs, including high-dose or multiple NSAIDs, and tell the pharmacist about acyclovir, valganciclovir, aminoglycosides and any other tenofovir-containing product.

This summarizes the official prescribing information. Your prescriber’s and pharmacist’s instructions, and the leaflet that comes with your medicine, take priority.

Why the cash price for Tenofovir Disoproxil differs from pharmacy to pharmacy

Generic 300 mg tablets are sold, so quotes for thirty tablets differ with the maker the pharmacy buys from and whether the drug is on a flat-price generic list. A prescription for the 150 mg tablet or the oral powder is a brand quote, and a prescription for Viread without substitution is priced as a brand and costs far more than the generics.

Treatment is long term, so the dispensing fee on each monthly fill adds up and a ninety-day fill spreads it. Tenofovir disoproxil is also sold inside combination tablets, which are separate products with their own quotes; the quote applies only to the single-ingredient tablet written.

Ways to pay less for Tenofovir Disoproxil without insurance

• Ask the prescriber to write tenofovir disoproxil fumarate generically and allow substitution.
• Once you are settled on treatment, ask the prescriber whether a ninety-day supply suits you, so you pay fewer dispensing fees and never run short, since stopping can trigger a hepatitis B flare.
• Ask whether the pharmacy has tenofovir disoproxil on a flat-price generic list, and compare more than one pharmacy.
• If a combination tablet containing tenofovir is prescribed instead, ask the prescriber whether separate generic components would suit you; do not change your regimen on your own.
• Upload the prescription to Script Unlock so licensed pharmacies can quote their cash price. You pay the pharmacy directly.

Questions to ask your pharmacist about Tenofovir Disoproxil

1. 1.Can my prescription be filled with a generic, and is the 300 mg tablet the right strength for my weight?
2. 2.Do any of my other medicines, such as an NSAID, acyclovir, an HIV protease inhibitor or a hepatitis C medicine, interact with my tenofovir?
3. 3.What should I do if I run out or miss doses, given the warning about hepatitis B flaring?
4. 4.When are my kidney and liver blood tests due, and who orders them?

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