Tenof EM (Emtricitabine and Tenofovir Disoproxil Fumarate) Tablets

Tenof-EM general information

What is Tenof-EM used for?

Tenof-EM tablets are a fixed dose combination antiretroviral treatment for Human Immunodeficiency Virus (HIV) infection in adults and adolescents aged 12 years and older, with body weight at least 35 kg.  Tenof-EM tablets are used combination with other medications that have a different mechanism of action to the components in Tenof-EM and can be used for patients who have already received treatment with other medications for HIV or as first line therapy for treatment-inexperienced patients.  However, Tenof-EM tablets should not be used for patients who have a history of treatment failure with other antiretroviral medications, or who have known mutations associated with resistance to the individual components in Tenof-EM tablets.  HIV impairs the immune system by attacking specific immune cells called CD4⁺ cells that are involved in fighting infection and this can lead to opportunistic, life-threatening infection (infections that would not normally be harmful); also if too many CD4⁺ cells are destroyed this can result in acquired immune deficiency syndrome (AIDS).  Tenof-EM tablets prevent or slow down the ability of HIV to replicate and spread, which keeps the amount of virus in the blood (viral load) down to a low level and this results in an increase in CD4⁺ cell numbers, so that the immune system can recover, reducing the risk of disease progression.   

How does Tenof-EM work?

Tenof-EM tablets contain a combination of two antiretroviral drugs, emtricitabine and tenofovir alafenamide, which are only effective against RNA viruses (retroviruses) like Human Immunodeficiency Virus (HIV).  These drugs each work by inhibiting the action of the viral-specific enzyme reverse transcriptase (RT), which is needed for the virus to be able to replicate.  Retroviruses convert RNA to DNA, which is then integrated into the DNA of infected immune cells so that the virus can replicate.  Emtricitabine in Tenof-EM tablets is a nucleoside analogue reverse transcriptase inhibitor (NRTI) and competes with the nucleoside cytidine.  Tenofovir alafenamide in Tenof-EM tablets is a prodrug of tenofovir, a nucleotide reverse transcriptase inhibitor (NtRTI) and competes with the nucleotide adenosine.  It is more efficient than tenofovir disoproxil fumarate in concentrating tenofovir in the HIV target cells, where it is converted into tenofovir.  Both emtricitabine and tenofovir alafenamide in Tenof-EM tablets work by blocking the action of RT, that is needed to transcribe the viral RNA into DNA, by becoming incorporated into the chain of newly synthesized viral DNA and preventing it from growing (chain termination).  The combined action of these two antiretroviral drugs in Tenof-EM tablets prevents the integration of the virus into the DNA of the infected CD4⁺ immune cell, which inhibits the replication of HIV so that no more virus can be produced, and this reduces the viral load (amount of virus).  Tenof-EM tablets slow down the replication of HIV within your body but does not kill the virus already incorporated in the CD4⁺ cells or prevent the spread of the infection to others. 

What does Tenof-EM contain?

Tenof-EM tablets contain a combination of the active ingredients emtricitabine and tenofovir alafenamide, which are antiretroviral drugs used to treat HIV infection. 

Treating HIV infection with Tenof-EM

Tenof-EM tablets contains two antiretroviral drugs, emtricitabine and tenofovir alafenamide, that are used to treat infection by Human Immunodeficiency Virus (HIV), which is an RNA virus (retrovirus), in combination with other medications that have a different mechanism of action to the components in Tenof-EM.  HIV impairs the immune system by attacking specific immune cells called CD4⁺ cells that are involved in fighting infection and this can lead to opportunistic life-threatening infection (infections that would not normally be harmful), including pneumonia, herpes virus infections, and Mycobacterium avium complex (MAC) infection.  If too many CD4⁺ cells are destroyed this can result in acquired immune deficiency syndrome (AIDS).  Both antiretroviral drugs in Tenof-EM tablets work by inhibiting the action of the viral-specific enzyme reverse transcriptase (RT) which is needed for the virus to be able to replicate.  Retroviruses convert RNA to DNA, which is then integrated into the DNA of infected immune cells so that the virus can replicate.  Emtricitabine in Tenof-EM tablets is a nucleoside analogue reverse transcriptase inhibitor (NRTI) and competes with the nucleoside cytidine.  Tenofovir alafenamide in Tenof-EM tablets is a prodrug of tenofovir, a nucleotide reverse transcriptase inhibitor (NtRTI) and competes with the nucleotide adenosine.  The combined action of the two antiretroviral drugs in Tenof-EM tablets prevents the integration of the virus into the DNA of the infected CD4⁺ immune cell, which inhibits the replication of HIV so that no more virus can be produced, and this reduces the viral load (amount of virus).  Tenof-EM tablets slow down the replication of HIV within your body but does not kill the virus already incorporated in the CD4⁺ cells or prevent the spread of the infection to others.

What are the side effects of Tenof-EM?

The most commonly reported side effects when taking Tenof-EM tablets include headache, gastrointestinal upset (nausea, diarrhoea, constipation, stomach pain), dizziness, fatigue, rash, difficulty sleeping, abnormal dreams, depression.  A more serious but less common side effect is a condition called lactic acidosis which is excess lactic acid in the blood due to liver damage, which may cause pancreatitis, liver failure, or renal failure.

What are the health risks when taking Tenof-EM?

Lactic acidosis is a rare but potentially fatal condition that has been reported when taking Tenof-EM tablets.  It is caused by a build up of excess of lactic acid in the blood due to liver damage, which is usually associated with hepatomegaly (liver enlargement) with steatosis (build up of fat in the liver) and may cause pancreatitis, liver failure, or renal failure.  Symptoms begin within a few months of treatment and include: nausea, vomiting and abdominal pain, difficulty breathing, loss of appetite, weight loss, motor weakness. 

When should Tenof-EM not be used?

You should not use Tenof-EM tablets if you:

• are allergic to emtricitabine and tenofovir alafenamide, or any ingredients in Tenof-EM
• are pregnant or are breastfeeding
• have kidney or liver disease
• have chronic hepatitis B (HBV) infection
• are using antiretroviral drugs containing lamivudine or other antiretroviral drugs that work by the same mechanism (nucleoside or nucleotide analogue reverse transcriptase inhibitors NRTI)
• are taking medicines that interact with Tenof-EM, including other retrovirals like didanosine, atazanavir, and ritonavir, herbal supplements like St John’s Wort, the antiepileptics phenytoin and carbamazepine

What medications interact with Tenof-EM?

Several medications interact with Tenof-EM tablets and should either not be taken while you are taking Tenof-EM or only after discussion and instruction from your doctor:

• Drugs that cause a serious reaction with Tenof-EM: didanosine for HIV
• Drugs that affect Tenof-EM: other retrovirals like ritonavir, herbal supplements like St John’s Wort, the antiepileptics phenytoin and carbamazepine
• Drugs that are affected by Tenof-EM: atazanavir for HIV

How should Tenof-EM be taken?

You should take your Tenof-EM tablets swallowed whole with a glass of water once a day with or without food.  You should continue to take your Tenof-EM tablets regularly for as long as recommended by your doctor and your condition should be monitored.  Do not suddenly stop taking your Tenof-EM tablets as this may increase risk of HIV resistance.

How long should you take Tenof-EM?

You should continue to take your Tenof-EM tablets regularly for as long as recommended by your doctor and your condition should be monitored.  Do not suddenly stop taking your Tenof-EM tablets as this may increase risk of HIV resistance.

Missed dose of Tenof-EM

If you miss a dose of Tenof-EM tablets take it as soon as you remember, unless it is time to take the next dose, then skip the missed dose.  Do not take a double dose.

How should Tenof-EM be stored?

You should store your Tenof-EM tablets below 25°C in a cool dry place.