Combivir (Lamivudine - Zidovudine)

What is Combivir expected to be used for?
This pill is used for treating HIV infection in combination with other pills. Combivir is an antiviral combination. Lamivudine and zidovudine are both nucleoside analogues that work together to slow the growth of HIV by blocking an enzyme needed by the virus to reproduce.

What should I know about Combivir?
During infection with HIV, the HIV virus multiplies within the body's cells. The newly-formed viruses are released from the cells and then spread throughout the body where they infect other cells. In this manner, the infection continually spreads to new, uninfected cells that the body is continually producing, and HIV infection is perpetuated. When producing new viruses, the HIV virus must manufacture new DNA for each virus.

Reverse transcriptase is the enzyme that the virus uses to form this new DNA. Lamivudine and zidovudine block the activity of reverse transcriptase and block the production of DNA and new viruses. (Specifically, lamivudine is converted within the body to its active form, lamivudine triphosphate, and zidovudine is converted to its active form, zidovudine triphosphate. The active forms are similar to the naturally occurring deoxycytidine triphosphate and thymidine triphosphate, respectively, chemicals that are used by reverse transcriptase to make DNA.

The reverse transcriptase uses lamivudine triphosphate and zidovudine triphosphate instead of the naturally-occurring deoxycytidine triphosphate and thymidine triphosphate for making DNA, and these active forms of the drugs interfere with the activity of reverse transcriptase.) The effectiveness of either lamivudine or zidovudine when used alone may decrease as the HIV virus develops resistance to the effects of the individual drugs.

By combining lamivudine and zidovudine, it is more difficult for the HIV virus to develop resistance to therapy since it must develop resistance to both pills. As a result, Combivir is more effective than lamivudine or zidovudine alone. Combivir does not kill existing HIV virus, and it is not a cure for HIV.

Combivir was approved by the FDA in September, 1997. Combivir provides two medicines in one pill. It can be more convenient to use Combivir than some other combinations of medicines. This could mean fewer missed doses and better control of HIV.

In which cases Combivir shouldn’t be used?
This medication should not be used if you are also taking stavudine, zalcitabine, or other medicines containing lamivudine or zidovudine. This medicine should not be used if you have certain medical conditions. Before using this medication, consult your medical assistant if you have:

• liver disease. Before using this product, tell your health care professional your medical history, including:
• kidney problems
• heart disease
• major injuries/surgeries/infections
• blood or bone marrow disorders
• allergies (especially drug allergies)
• hepatitis B virus infection
• alcoholism

What is important safety information for Combivir?

• Changes in body fat (for example, an increased amount of fat in the upper back, neck, breast, and trunk, and loss of fat from the legs, arms, and face) may occur in some patients taking Combivir. The cause and long-term effects of these changes are unknown. Discuss any concerns with your medical assistant.
• Do not stop taking Combivir without first checking with your medical assistant. Some conditions, including hepatitis B, may become worse if Combivir is suddenly stopped.
• Combivir should not be used in KIDS weighing less than 66 lbs (30 kg); safety and effectiveness in these kids have not been confirmed. Caution is advised when using Combivir in KIDS with a history of pancreatitis, or kids who have taken other drugs for HIV infection.
• Lab tests, including blood cell counts and liver and kidney function tests, may be performed while you use Combivir. These tests may be used to monitor your condition or check for side effects. Be sure to keep all health care professional and lab appointments.
• When your medication supply is low, get more from your health care professional as soon as you can. Do not stop taking Combivir, even for a short period of time. If you do, the virus may grow resistant to the medication and become harder to treat.
• Combivir does not stop the spread of HIV to others through blood or sexual contact. Use barrier methods of birth control (for example, condoms) if you have HIV infection. Do not share needles, injection supplies, or items like toothbrushes or razors.
• The risk of side effects may be greater and additional benefits may not be obtained if you take Combivir in high doses. Do NOT take more than the recommended dose without checking with your medical assistant.
• PREGNANCY and BREAST-FEEDING: If you become pregnant, contact your doctor. You will need to discuss the benefits and risks of using Combivir while you are pregnant. Combivir is found in breast milk. Do not breast-feed while taking Combivir. Mothers infected with HIV should not breast-feed. There is a risk of passing the HIV infection or Combivir to the baby.
• Combivir may cause drowsiness or dizziness. These effects may be worse if you take it with alcohol or certain drugs. Use Combivir with caution. Do not drive or perform other possibly unsafe tasks until you know how you react to it.
• Combivir is not a cure for HIV infection. Patients may still get illnesses and infections associated with HIV. Remain under the care of your doctor.

How is Combivir expected to be taken?
Use Combivir as directed by your medical assistant. Check the label on the medicine for exact dosing instructions.

• Take Combivir by mouth with or without food. Usual dosage is one tablet twice daily.
• Continue to use Combivir even if you feel well. Do not miss any doses.
• Taking Combivir at the same time each day will help you remember to take it. Ask your doctor any questions you may have about how to use Combivir.

What should I do if I have MISSED a DOSE?
If you miss a dose, use it as soon as you remember. If it is within 2 hours of the next dose, skip the missed dose and resume your usual dosing schedule. It is important not to miss doses of this medicine.

What should I do if OVERDOSE is suspected?
Contact Emergency Medical Service at once. Symptoms may include:

• confusion
• headache
• seizures
• nausea
• dizziness
• tiredness
• vomiting
• drowsiness

What are possible side effects of Combivir?
All drugs may cause side effects, but many people have no, or minor, side effects. Consult with your doctor if any of these most COMMON side effects persist or become bothersome:

• indigestion
• diarrhea
• nasal problems
• tiredness
• dizziness
• weakness
• appetite loss
• changes in body fat
• fatigue
• headache
• cough
• sleeplessness or other sleep problems

• seizures
• dark urine
• infection (sore throat, fever, chills)
• nausea
• shortness of breath
• fast or irregular heartbeat
• swelling or soreness of the mouth or tongue
• numbness, tingling, or weakness in arms or legs
• Severe allergic reactions (rash, swelling of the mouth, face, lips, or tongue, difficulty breathing, hives, tightness in the chest, itching)
• muscle pain
• yellowing of the skin or eyes
• depression
• inflammation of the pancreas (vomiting, severe stomach pain, nausea)
• joint pain
• stomach tenderness or pain
• mental or mood changes
• unusual weakness or exhaustion
• unusual tiredness
• unusual bleeding or bruising
• vomiting

What are possible interactions of Combivir with other drugs?
Some MEDICINES MAY INTERACT with Combivir. Tell your medical assistant if you are taking any other pills, especially any of the following:

• zalcitabine, clarithromycin, rifampin or doxorubicin because they may decrease Combivir's effectiveness
• interferon alfa or ribavirin because serious liver problems may occur
• stavudine because its effectiveness may be decreased by Combivir
• ibuprofen, ganciclovir, valproic acid, methadone, probenecid, trimethoprim/sulfamethoxazole, zalcitabine, acetaminophen or vancomycin because they may increase the risk of Combivir 's side effects or toxic effects

What should be proper storage of Combivir?
Store Combivir at room temperature or in the refrigerator, between 36 and 86 degrees F (2 and 30 degrees C). Store in a tightly closed container. Store away from heat, moisture, and light. Do not store in the bathroom. Keep Combivir out of the reach of kids and away from pets.