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• Overview

  Tenofovir disoproxil fumarate, a prodrug of tenofovir[Trade name: “Viread”] developed by Gilead Sciences, is a kind of nucleotide-analogues antiretroviral drugs, taking effect through acting as the reverse transcriptase inhibitors[nRTIs], which block reverse transcriptase, an enzyme crucial to viral production in HIV-infected people^[1-4]. It should be noted that it is the first nucleotide reverse transcriptase inhibitor that has ever used for the treatment of HIV infection^[5]. Tenofovir disoproxil fumarate is converted to tenofovir in vivo, which is an acyclic nucleoside phosphonate[nucleotide] analog of adenosine 5'-monophosphate^[5,6]. It is generally used in combination with other kinds of medicine. HIV medicines can't cure HIV/AIDS, but taking a combination of HIV medicines[called an HIV regimen] every day can help people with HIV live longer, healthier lives^[7]. Based on the FDA document, tenofovir disoproxil fumarate can also be for the treatment of chronic hepatitis B virus[HBV] infection in adults and children 12 years of age and older^{[1,3, 4, 8]}. ;

• Indication and application

  Tenofovir disoproxil fumarate[trade name: Viread®], an antiviral drug, is indicated as the treatment for both HIV and Hepatitis B virus[HBV]. Viread® is indicated in combination with other antiretroviral agents for the treatment of HIV-1 infection in adults and pediatric patients 2 years of age and older. It is also indicated for the treatment of chronic hepatitis B in adults and pediatric patients 12 years of age and older^[2,9]. ;

• Mode of action

  Tenofovir[the prodrug type of Viread] can effectively inhibit the activity of HIV reverse transcriptase by competing with the natural substrate deoxyadenosine 5'-triphosphate and, after incorporation into DNA, leading to DNA chain termination^{[1, 5, 7, 8]}. Specifically, the drugs are analogues of the naturally occurring deoxynucleotides needed to synthesize the viral DNA and they compete with the natural deoxynucleotides for incorporation into the growing viral DNA chain^{[8, 10, 11]}. However, unlike the natural deoxynucleotides substrates, NRTIs and NTRTIs[nucleoside/tide reverse transcriptase inhibitors] lack a 3'-hydroxyl group on the deoxyribose moiety. As a result, following incorporation of an NRTI or an NtRTI, the next incoming deoxynucleotide cannot form the next 5'-3' phosphodiester bond needed to extend the DNA chain. Thus, when an NRTI or NtRTI is incorporated, viral DNA synthesis is halted, a process known as chain termination. All NRTIs and NtRTIs are classified as competitive substrate inhibitors^[2]. ;

• Adverse reactions

  Common adverse reactions include back pain, headache, lack or loss of strength, pain, redness of the skin, skin rash as well as itching skin^[3]. Severe adverse reactions of Tenofovir disoproxil fumarate may include severe acute exacerbation of Hepatitis, new onset or worsening renal impairment, lactic acidosis/severe hepatomegaly with steatosis, bone effects and immune re-constitution syndrome and liver impairment^[3]. Some less common side effects include chest pain, cough, fever of chills, weight loss, joint pain and swelling, itching and crawling tightness in the chest and trouble in breathing. In rare cases, abdominal or stomach discomfort, decreased appetite, diarrhea, fast, shallow breathing, general feeling of discomfort, muscle pain or cramping, unusual tiredness or weakness could occur^{[4, 9]}. ;

• Warning and precaution

  Viread should not be taken together with adefovir[Hepsera], or with used in combination with medicines that contain tenofovir[Atripla, Biktarvy, Cimduo, Complera, Descovy, Genvoya, Odefsey, Stribild, Symfi, or Truvada]. If patients have ever had chronic hepatitis B, Viread can restore the condition or even worse it. In this case, frequent blood tests is required to check your liver function. Do not stop using tenofovir disoproxil without first talking to your healthcare providers. This medicine may cause a serious condition called lactic acidosis^{[1, 3, 4, 9]}.
  Get emergency medical help if you have even mild symptoms such as: muscle pain or weakness, numb or cold feeling in your arms and legs, trouble breathing, stomach pain, nausea with vomiting, fast or uneven heart rate, dizziness, or feeling very weak or tired. Viread can also cause severe or life-threatening effects on your liver. Call your doctor at once if you have: nausea, upper stomach pain, itching, loss of appetite, dark urine, clay-colored stools, jaundice[yellowing of the skin or eyes]^{[3, 4, 9]}.
  Children with HIV who are younger than 2 years old as well as children with hepatitis B who are younger than 12 years old should be disabled from using Viread^{[3, 9]}.
  Patients who have liver diseases, kidney disease or with low bone mineral density should ask doctors for advice before taking Viread. It may be not that safe for Women during pregnant or lactation stage to take Viread, so consult doctors before using it^[3].
  Bone mineral density monitoring should be considered in patients who have a history of pathologic bone fracture or at risk for osteopenia^[9].
  Some more tips:
  Avoid sharing needles or other injection equipment as well as personal items that can have blood or body fluids on them, liketoothbrushes and razor blades. Avoid having any kind of sex without protection. Always practice safer sex by using a latex or polyurethane condom to lower the chance of sexual contact with semen, vaginal secretions, or blood. Avoid breastfeed since tenofovir is excreted in breast milk and it is not known whether it can harm the baby. Mothers with HIV-1 should not breastfeed because HIV-1 can be passed to the baby in the breast milk^[9].
  Viread may cause either lactic acidosis or severe liver problem. Ask the doctor for help immediately when you have the following symptoms: feeling weak or tired, unusual muscle pain, trouble breathing, stomach pain associated with nausea or vomiting, feeling dizzy or lightheaded, fast or irregular heartbeat or cold or blue hands or feet, yellowing skin and whiting eye, dark-colored unit, loss of appetite, nausea and light-colored bowel movement^[3,9]. ;

• References

  1. Editor, Text. "New Antiretroviral for HIV Infection. approved by the FDA tenofovir disoproxil fumarate Viread." American Family Physician[2002].
  2. https://www.drugbank.ca/drugs/DB00300
  3. https://aidsinfo.nih.gov/drugs/290/tenofovir-disoproxil-fumarate/0/patient/
  4. https://www.drugs.com/pro/viread.html
  5. Coleman, C., J. Ross, and P. Reddy. "Tenofovir disoproxil fumarate: The first nucleotide reverse transcriptase inhibitor for treatment of patients with HIV-1 infection." Formulary[2002].
  6. Cooper, R. D, et al. "Systematic review and meta-analysis: renal safety of tenofovir disoproxil fumarate in HIV-infected patients. " Clinical Infectious Diseases 51.5(2010]:496-505.
  7. Lysengwilliamson, K. A., N. A. Reynolds, and G. L. Plosker. "Tenofovir disoproxil fumarate: a review of its use in the management of HIV infection. " Drugs 65.8(2005]:413-432.
  8. Heathcote, E. J., et al. "Three-year efficacy and safety of tenofovir disoproxil fumarate treatment for chronic hepatitis B. " Gastroenterology140.1(2011]:132-143.
  9. https://www.rxlist.com/viread-drug.htm#indications_dosage
  10. Miller MD, Margot NA, Hertogs K, Larder B, Miller V: Antiviral activity of tenofovir[PMPA] against nucleoside-resistant clinical HIV samples. Nucleosides Nucleotides Nucleic Acids. 2001 Apr-Jul;20(4-7]:1025-8.
  11. Buti, M, and M. Homs. "Tenofovir disoproxil fumarate in the treatment of chronic hepatitis B." Expert Rev Gastroenterol Hepatol 6.4(2012]:413-421.
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