What is Abacavir?
Abacavir is an oral medication used to treat infections associated with the Human Immunodeficiency Virus (HIV). It belongs to a class of drugs called reverse transcriptase inhibitors that prevent the multiplication of HIV. It is routinely used with other medications as part of Highly Active Antiretroviral Therapy (HAART).
How Does Abacavir Work?
HIV needs to form new DNA to produce new viruses and multiply. The virus uses an enzyme called reverse transcriptase (RT) to create the new viral DNAs in the host (humans, animals).
This enzyme is usually found in retroviruses like Human Immunodeficiency Virus or HIV.
When Abacavir is consumed, it gets converted into its active form called carbovir triphosphate in the body. This compound is similar to deoxyguanosine triphosphate, a compound used by the HIV virus to make new DNA.
The RT enzyme now uses carbovir triphosphate instead of deoxyguanosine triphosphate for making DNA. This interferes with viral replication, slowing down the multiplication of HIV.
Abacavir does not kill HIV and is not a cure for the disease either.
Side Effects of Abacavir
Some common side effects of Abacavir are:
- Headache
- Depression
- Anxiety
- Difficulty in falling and staying asleep
- Loss of appetite
Serious side effects of the drug include:
- Unexplained weight loss
- Muscle aches
- Tiredness and fatigue
- Persistent headaches
- Joint pain
- Numbness and tingling of hands, legs, arms, and feet
- Changes in vision
- Hives
- Itching
- Difficulty in swallowing and breathing
- Blisters or peeling of skin
- Light-colored bowel movements
- Yellowing of skin and eyes
- Changes in the immune system
- Increased risk of heart attack
Interactions With Other Drugs
Abacavir shows interactions with other drugs, so it is essential to inform your doctor about the medications you may be taking. Some medicines that may interact with Abacavir are:
- Methadone ( a drug used in chronic pain management and treatment of opioid drug dependence)
- Epzicom (a prescription drug used to treat symptoms of HIV infection)
- Trizivir (a drug used to treat HIV/AIDS infection)
Abacavir: Gene-Drug Interactions
HLA-B Gene and Abacavir
The HLA-B gene is a part of the Human Leukocyte Antigen (HLA) complex family. This complex helps the body’s immune system differentiate between proteins made by the body and infectious pathogens like bacteria and viruses.
There are many types of the HLA-B gene that allow the immune system to respond to a wide range of pathogens. The HLA-B gene alleles are numbered as HLA-B *x, where x is a numerical figure. For example, HLA-B*57, HLA-B*35, etc.
Closely related alleles that are categorized together are numbered as HLA-B *57: 01 to HLA-B*57:60 (if there are around 60 very similar alleles that are subtypes of HLA-B57)
HLA-B*57:01 allele increases the risk of hypersensitivity reactions to Abacavir across different ethnicities.
In addition, the presence of HLA-B*57:01 significantly increases the risk of hypersensitivity reactions with Abacavir usage.
Abacavir is, therefore, not indicated or prescribed for patients with HLA-B*57:01 allele and those with a prior history of hypersensitivity reaction to Abacavir.
rs2395029
rs2395029 is a single nucleotide polymorphism or SNP in the HLA-B gene. The G allele of this SNP is 99.9% predictive of the presence of an HLA-B*5701 allele in Caucasian and Hispanic populations.
| Genotype | Effect |
| GG | HLA-B*57:01 homozygote likely if the individual is Caucasian or Hispanic. High risk for hypersensitivity to drugs like Abacavir |
| GT | Most likely a carrier of the HLA-B*57:01 if the individual is Caucasian or Hispanic. |
| TT | No risk of sensitivity to abacavir |
Recommendations for Safe Consumption of Abacavir
- Pre-existing liver or cardiac conditions
Before taking Abacavir, you must inform your doctor if you have a history of liver or kidney problems.
Abacavir may increase your risk for heart attack, and you must consult your doctor if you have any cardiovascular condition that can precipitate an attack.
It is also essential to inform your doctor about your history of alcohol consumption, smoking, hypertension, diabetes, and high cholesterol levels.
- Current Medications
If you are on medications like methadone or other retrovirals for HIV, you must inform your doctor and pharmacist to avoid untoward drug interactions.
- Appropriate Dosage
The recommended dosage of Abacavir is 300 mg orally twice a day or 600 mg once a day (for healthy adults, adolescents, and children weighing at least 25 kg). The drug is available as a solution (20 mg/mL) and tablet (300 mg).
- History of Allergies
Before taking Abacavir, you must inform your doctor if you are allergic to the drug or have a history of allergies to any substance or other medications.
- Pregnancy and Breastfeeding
Inform your doctor if you are pregnant before starting on Abacavir. Treatment using this drug can lower the transmission of HIV to your fetus.
This drug can pass into breast milk. Therefore, avoiding breastfeeding may be recommended during treatment with the drug.
- Genetic Testing
Screening for the HLA-B*57:01 allele is recommended for all patients according to the FDA drug label for Abacavir.
Analyze Your Genetic Response to Abacavir
Video
Summary
- Abacavir is an oral reverse transcriptase inhibitor drug used with other medications for the treatment of HIV.
- Carbovir triphosphate, the active form of Abacavir, interferes with HIV’s multiplication process and slows down the disease progression.
- Abacavir may cause side effects like headaches, depression, anxiety, and loss of appetite.
- If you experience severe side effects like unexplained weight loss, muscle aches, fatigue, tiredness, joint aches, etc., you must consult your doctor immediately.
- Abacavir interacts with methadone and some drugs used in HIV treatment.
- The HLA-B gene participates in the immune response reactions of the body. HLA-B*57:01 allele of the gene increases the risk of hypersensitivity reaction to Abacavir.
- For safe consumption of Abacavir, you must inform your doctor about your medical and drug history.
- The recommended dosage of Abacavir is 300 mg orally twice a day or 600 mg orally once a day.
- Lactating women who are HIV positive and taking Abacavir may be recommended to avoid breastfeeding their babies.
- To prevent any allergic reaction to Abacavir, screening for the high-risk HLA-B*57:01 allele is recommended.
