In the news -Today reports better Life For Singaporean HIV Patients; Highest cases of HIV in Eastern Europe reported by WHO; The CDC in the US says HIV Prophylaxis can help millions
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Tenofovir (Viread®) was invented by Antonín Holý from at the Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic and patented in 1984, making this one of the earliest antiviral drugs. In collaboration with Gilead Sciences and the University of California, it was developed into its current form and was approved for use against HIV in 2001. It is now also being used for the Post-Exposure Prophylaxis of HIV.
Viread® is a defective nuclease that lacks the OH- group of the deoxyribose sugar. Because of this lack, when the Viread® particle is incorporated into the DNA strand, no other deoxyribose sugars can be added, terminating production. Viread® does not interact well with human DNA polymerases and so does not have a large effect on normal cell replication. It does interact with the viral reverse transcriptase that changes the viral RNA into DNA, preventing viral replication in the host cell.
Side effects
The most common side effects with Viread® are gastrointestinal upsets such as loss of appetite, stomach ache, nausea, gas, cramping, diarrhoea and vomiting. Patients can also experience a skin rash, insomnia, headaches, dizziness and depression.
Like Emtriva® it can cause lactic acidosis so patients should be on the look out for sore muscles for no reason, fatigue, chills in the limbs and irregular heartbeat or trouble breathing. Lactic acidosis can be fatal if left untreated so it is important to seek urgent medical care should you start to exhibit these symptoms. Be aware this is a rare side effect.
Liver toxicity can occur so watch for jaundice, dark urine, light stools and fatigue. Viread® has also been linked to decreases in bone mineral density so it may be wise to speak to your doctor about supplements while taking Viread®.
Contraindications
People with pre-existing liver damage should be carefully monitored while taking Viread®, particularly those with viral hepatitis.
Lactic acidosis is more commonly seen in females, people who are overweight and those who have been taking HIV medication for an extended period of time.
Alcohol can exacerbate liver conditions so it is best to avoid heavy drinking while taking Viread®. The drug has been shown to increase symptoms of hepatitis for those suffering viral hepatitis B (HBV), though the drug itself has been approved for treatment of the HBV under controlled conditions. Be sure to inform your doctor if you have HBV so that the correct dose can be administered and liver function monitored. Patients with HBV have shown a significant increase in pathological symptoms following discontinuation of Viread® so should be monitored when coming off the course.
Those with a history of osteoporosis or other bone disorders should speak to their doctor before taking Viread®.
There is no evidence to say that Viread® is dangerous during pregnancy but insufficient data to claim it is safe. As a consequence, it should be given only in the utmost need to pregnant women. Viread® is transmitted through the breast milk, as is any live HIV virus and it is advised that those women on Viread® do not breastfeed.
Drug interactions
Due to the method of clearance from the body via the kidneys it is advised that you avoid mixing Viread® with nephrotoxic (nephron=kidneys) drugs. Viread® has not been linked to kidney failure but it is still advised that kidney function is monitored. It is recommended for patients on didanosine that the didanosine is reduced or discontinued while as Viread® will increase didanosine bioavailability which can cause damage to the kidneys or pancreas.
Viread® should not be given along with HEPSERA.
Viread® is not the only drug to contain tenofovir and it is important to ensure the correct dose. Inform your doctor if you are taking any other anti-HIV medications to prevent overdosing. Often increasing the dose will not increase effectiveness against HIV but will exacerbate the side effects so it is important not to double up.
There is some evidence to show that Viread® bioavailability levels are boosted by the presence of Kaletra® in the patient’s system.
Additional information
Viread® is one of the oldest anti-HIV drugs and as it acts on the DNA itself rather than a protein, resistance is rare though it does occur. It is listed on the World Health Organisations list of essential medicines for the treatment of HIV and has proved its worth in the fight to stem the tide of AIDS.
Recent studies show that Viread® may have a larger role to play than just as an anti-HIV drug. Patients with HBV have shown a reduction in viral load when taking Viread® and some have been shown to clear the HBV virus entirely from their system when taking Viread®. Despite this FDA has not approved Viread® for treatment of co-infection with HIV and HBV, concerned about the hepatotoxicity (hepato = liver) of Viread®. The situation is very different in Britain where Viread® is the first drug of choice for treating HIV and HBV co-infection.
The jury is still out on which approach is the correct one. This older of the HIV drugs may well give hope to those who are suffering a chronic HBV infection. Hepatitis C can now be cured in up to 80% of cases with correct administration of anti-virals. It may be that a solution to HBV is on the horizon.
For more information see:
WebMD – Viread
http://www.webmd.com/drugs/2/drug-22106-6330/Viread®-oral/tenofovir-oral/details
Gilead Sciences product information sheet – Viread
http://www.gilead.com/~/media/files/pdfs/medicines/liver-disease/Viread®/Viread®_pi.pdf
The New York State Department of Health AIDS Institute (NYSDHAI) recently tasked their Medical Care Criteria Committee (MCCC) to update their HIV PEP (Post-exposure Prophylaxis) guidelines. PEP refers to the treatment required and administered after exposure to HIV – a sexually transmitted disease (STD). This exposure is categorised as resulting from sexual assault, occupational exposure, and non-occupational exposure.
In 2012, the recommended medications for post-exposure treatment was the use of tenofovir [Viread®] with emtricitabine [Emtriva®] (or lamivudine [Epivir®]) and raltegravir [Isentress®] – due mainly to the higher rate of completion of the shorter 28-day course of treatment. In 2014, however, dolutegravir [Tivicay®] was added as an alternative to raltegravir [Isentress®]. Dolutegravir is an approved antiretroviral drug designed to block the action of the virus. This change was initiated to further improve the rate of completion of the course of medication based on the side-effects and dosage requirements of dolutegravir [Tivicay®] which have displayed improved tolerability.
The MCCC reported that the efficacy of the above mentioned medications may be compromised when taken alongside aluminium, calcium, iron, or magnesium. Being mindful of the presence of these minerals in food and over the counter antacids was particularly emphasised. As such it was stated that antacids should be taken a minimum of 2 hours before and 6 hours after the medication to receive the maximum benefits of the drugs.
Due to the 6 week window period during which the virus can spread undetected, the committee expressed the need to perform a laboratory blood test (HIV RNA test) even if the patient tests negative during the initial screening test. A newer fourth-generation HIV test was suggested for a more accurate result and the importance of all patients being tested was emphasised.
The recommendations stated that PEP must, as a matter of urgency, begin within 2 hours after exposure while awaiting results of the patient’s baseline tests. Baseline testing refers to the initial tests conducted and includes an immune function test (CD4 count); HIV replication test (viral load); kidney, liver, cholesterol, and blood cell tests; and tests for accompanying viruses or diseases. Baseline testing is required even in cases where PEP treatment is declined.
It was further recommended that patients receive access to psychological counselling and support in order to improve their adherence to guidelines and provide the necessary framework for the completion of treatment.
The committee later updated their recommendations to include further HIV testing at 4 weeks and 12 weeks after exposure and added that routine testing at 6 months is unnecessary in the event that the 12 week test yields a negative result for the presence of HIV. It was clarified that pre-exposure treatment should be explained and made available to individuals who display high-risk sexual activity in the case of non-occupational exposure.
In a public announcement in April 2015, the Governor of New York revealed a detailed plan to reduce new HIV infections. The Blueprint to End the AIDS Epidemic outlines the plan which requires changes to regulation, and a critical look at the state of existing medical infrastructure in order for implementation to be successful.
The uniting feature of similarity between the Governor’s announcement and the Committee’s recommendations was the emphasis on promoting education among both medical personnel and the general public. Numerous campaigns have been launched to this end including the distribution of resources to the relevant clinics and a written inventory of the resources available. The underlying factors for success in reducing HIV infections remains in the availability of resources, education, and expenses.