How does it work?

Viread tablets contain the active ingredient tenofovirdisoproxil fumarate, which is a type of medicine called a nucleotide reversetranscriptase inhibitor. It is used in the treatment of HIV (humanimmunodeficiency virus) infection and chronic hepatitis B infection.

AIDS(acquired immune deficiency syndrome) is caused by infection with HIV. Thisvirus invades cells of the immune system, particularly the white blood cellsknown as CD4 T-helper lymphocytes. These cells normally work to activate othercells in the immune system to fight infection. Since HIV kills CD4 T-helpercells, over time the body becomes less able to fight the virus or subsequentinfections.

Oncethe virus is inside the CD4 T-cell it multiplies. Part of the process of viralmultiplication involves the conversion of the virus genetic material, RNA, intoDNA. This is achieved by a compound essential to the virus, called reversetranscriptase. Reverse transcriptase is a compound known as an enzyme.Tenofovir works by blocking the action of this enzyme, thereby interfering withthe conversion of viral RNA into DNA. This stops the virus from multiplying.

There isno cure for HIV, but tenofovir is one of a number of medications that lowersthe amount of virus in the body (viral load) and slows the progression of thedisease from HIV to AIDS. Tenofovir must be used in conjunction with otheranti-HIV drugs that attack the HIV virus in different ways. It can be used asone of the first medicines to treat people who have not yet started anti-HIVmedicines. It can also be added to existing treatment in people who are failingan antiretroviral regimen because their virus has become resistant, and is notresponding to the existing treatment.

Tenofovir can also be used to treat chronic hepatitis B infection. Hepatitis B is a virus that infects the liver and leads to liver damage. Once the virus is inside the liver cells it multiplies. Part of this process involves the virus making copies of its genetic material (DNA). This is achieved by a compound essential to the virus, called viral DNA polymerase. Viral DNA polymerase is a compound known as an enzyme. Tenofovir works by blocking the action of this enzyme. This stops the virus from multiplying.Tenofovir lowers the amount of hepatitis B virus in the body. This leads to a reduction in liver damage and an improvement in liver function.

What is it used for?

• HIV infection.
• Chronic hepatitis B infection.

Warning!

• This medicine should be taken with or after food, as food increases the absorption of the medicine into the body.
• The HIV virus is very good at becoming resistant to anti-HIV medicines. For this reason it is very important that you carefully follow your doctor's instructions for taking your anti-HIV medicines, in order to maintain effective levels of the medicines in your blood. If the blood levels drop, the virus will be given more chance to replicate and develop resistance to the drugs. Skipping even a few doses increases the risk of treatment failure, so you should try to ensure that you take all your doses at the correct time, and that you visit your doctor for repeat prescriptions before you run out.
• Treatment of HIV or hepatitis B infection with this medicine does not reduce the risk of transmitting the virus to other people through sexual contact or blood contamination. You should continue to use condoms to prevent transmitting the virus to your sexual partner.
• If you have any problems with your liver, in particular chronic hepatitis B or C, your liver function should be monitored while you are taking this medicine.
• Your kidney function should be monitored prior to starting and regularly throughout treatment with this medicine. Monitoring is recommended every four weeks during the first year of treatment, and then every three months. Your doctor may want to monitor your kidney function more frequently than this if you already have, or are at risk of, kidney problems.
• The class of medicines that tenofovir is related to can cause a rare but serious condition called lactic acidosis, which is an excess of lactic acid in the blood, together with an enlarged liver. This side effect is more likely to occur in overweight women and people with liver disease (particularly hepatitis C treated with alpha interferon and ribavirin). If it occurs, lactic acidosis usually develops after a few months of treatment. Your doctor will monitor you for this side effect, but symptoms that might indicate it's development include rapid and/or deep breathing and non-specific symptoms such as feeling weak, sick or generally unwell, vomiting, abdominal pain, loss of appetite or weight loss. You should tell your doctor if you experience any of these.
• Combination antiretroviral therapy has been associated with a redistribution of body fat (lipodystrophy) in people with HIV. This may include loss of fat from the face and limbs, increased fat in the abdomen and internal organs, breast enlargement and fatty lumps at the back of the neck (buffalo hump). The long-term consequences of this are currently unknown, however your doctor may wish to monitor your body fat, and the levels of lipids (eg cholesterol) and sugar (glucose) in your blood, and may prescribe additional medicines for any lipid disorders that occur during treatment with this medicine. Contact your doctor if you notice any changes in your body fat during treatment with your HIV medicines.
• Some people being treated with combination antiretroviral therapy for HIV may develop a bone condition called osteonecrosis. This condition is caused by loss of blood supply to a bone, causing death of the bone tissue. The risk of the condition is thought to be increased by corticosteroid use, alcohol consumption, severe immunosuppression, higher body mass index, advanced HIV disease and long-term use of antiretroviral medicines. If you notice any joint stiffness, aches and pains (especially of the hip, knee and shoulder) or difficulty in movement while using this medicine, you should tell your doctor so this can be investigated.

Use with caution in

• Decreased kidney function.
• People at risk of or with a history of kidney problems.
• Elderly people.
• Obese women.
• Liver disease.
• Enlarged liver (hepatomegaly).
• Hepatitis, especially chronic hepatitis B or C.
• History of alcohol abuse.

Not to be used in

• Allergy to any ingredient.
• Rare hereditary problems of galactose intolerance, the Lapp lactase deficiency, or glucose-galactose malabsorption (Viread tablets contain lactose).
• The safety and efficacy of this medicine have not been studied in children and adolescents under 18 years of age, or in elderly people over 65 years of age. It is not recommended for these age groups.

This medicine should not be used if you are allergic to one orany of its ingredients. Please inform your doctor or pharmacist if you havepreviously experienced such anallergy.If you feel you haveexperienced an allergic reaction, stop using this medicine and inform yourdoctor or pharmacist immediately.

Pregnancy and breastfeeding

Certain medicines should not be used during pregnancy orbreastfeeding. However, other medicines may be safely used in pregnancy orbreastfeeding providing the benefits to the mother outweigh the risks to theunborn baby. Always inform your doctor if you are pregnant or planning apregnancy, before using any medicine.

• The safety of this medicine during pregnancy has not been investigated. Since the effects on a developing foetus are unknown, women who could get pregnant should use effective contraception to prevent pregnancy while taking this medicine. The medicine should not be used during pregnancy unless the benefits outweigh the potential risks to the foetus. Seek medical advice from your doctor.
• It is not known if this medicine passes into breast milk. Mothers who need to take this medicine should not breastfeed their infants.
• It is recommended that women infected with the HIV or hepatitis B virus should not breastfeed their infants under any circumstances, and regardless of their treatment, in order to avoid passing the virus to the baby via their breast milk. Seek further medical advice from your doctor.

Label warnings

• Take this medication with or after food.

Side effects

Medicines and their possible side effects can affect individualpeople in different ways. The following are some of the side effects that areknown to be associated with this medicine. Just because a side effect is statedhere does not mean that all people using this medicine will experience thator any side effect.

• Low level of phosphate in the blood (hypophosphataemia).
• Dizziness.
• Headache.
• Nausea and vomiting.
• Diarrhoea.
• Excess gas in the stomach and intestines (flatulence).
• Abdominal pain or bloating.
• Fatigue.
• Rash.
• Inflammation of the pancreas (pancreatitis).
• Elevated levels of lactic acid in the blood (lactic acidosis - see warning above).
• Kidney problems, including kidney failure.
• Difficulty breathing (dyspnoea).
• Weakness or loss of strength (asthenia).

The side effects listed above may not include all of the sideeffects reported by the medicine'smanufacturer.For moreinformation about any other possible risks associated with this medicine,please read the information provided with the medicine or consult your doctoror pharmacist.

How can this medicine affect other medicines?

It is important to tell your doctor or pharmacist what medicinesyou are already taking, including those bought without a prescription andherbal medicines, before you start treatment with this medicine. Similarly,check with your doctor or pharmacist before taking any new medicines whiletaking this one, to ensure that thecombination is safe.

There may be an increased risk of kidney problems if thismedicine is taken with other medicines that may have side effects on thekidneys. These include the following:

• adefovir (should not be used in combination with tenofovir)
• aminoglycoside antibiotics, eg gentamicin, neomycin
• amphotericin B
• cidofovir
• foscarnet
• ganciclovir
• interleukin-2
• pentamidine
• tacrolimus
• vancomycin.

Where possible these medicines should be avoided in combinationwith tenofovir, however, if they are considered necessary by your doctor thenyou should have your kidney function monitored weekly.

Nucleoside reverse transcriptase inhibitors, such as abacavir,emtricitabine, didanosine, lamivudine, stavudine, zalcitabine and zidovudine,are closely related to this medicine. They are associated with a side effectcalled lactic acidosis (excess of lactic acid in the blood). The risk of thisside effect with tenofovir is low, but if you are taking any of these medicineswith tenofovir your doctor will monitor you regularly. You should inform yourdoctor if you experience symptoms such as nausea, vomiting and stomach pain(see warning above), as these might indicate the development of lacticacidosis.

Tenofovir may increase the blood level of didanosine and hencemay increase the risk of its side effects. Studies using lower doses ofdidanosine to avoid this problem have shown a high rate of early virologicalfailure and emergence of resistance. For this reason, using tenofovir incombination with didanosine is not recommended, particularly in people with ahigh viral load and low CD4 count. If your doctor feels it is necessary to takethese medicines together, your viral load and CD4 counts should be regularlychecked, and you should be monitored for any possible side effects ofdidanosine, in particular pancreatitis and lactic acidosis.

There have been reports of a high rate of virological failureand the emergence of resistance at early stage in HIV patients when tenofovir was combined withlamivudine plus abacavir as triple therapy. This problem has also occured whentenofovir was combined with lamivudine plus didanosine as tripletherapy.

The blood level of this medicine may be increased if it is takenin combination with lopinavir/ritonavir or atazanavir/ritonavir.

This medicine should not be used in combination with any other medicines that contain tenofovir (Truvada or Atripla).

Other medicines containing the same active ingredient

There are currently no other medicines available in the UK that containtenofovir as the only active ingredient.

Truvada containstenofovir in combination with another anti-HIV medicine calledemtricitabine.

Atriplacontainstenofovir in combination with two other anti-HIV medicines calledefavirenz and emtricitabine.