How does this medication work? What will it do for me?
Efavirenz belongs to the class of medications called non-nucleoside reverse transcriptase inhibitors (NNRTIs). Efavirenz is used in a combination with other anti-HIV drugs to treat the infection caused by the human immunodeficiency virus (HIV). HIV is the virus responsible for acquired immune deficiency syndrome (AIDS).
Reverse transcriptase is a part of HIV virus required to infect cells and make more virus. Efavirenz prevents reverse transcriptase from working properly.
This medication does not cure AIDS and does not prevent it from being spread to others. It does slow further growth or reproduction of HIV virus when used in combination with other drugs, and it seems to slow down the destruction of the immune system. This may help to delay the development of problems that are related to AIDS or HIV.
Your doctor may have suggested this medication for conditions other than those listed in these drug information articles. As well, some forms of this medication may not be used for all of the conditions discussed here. If you have not discussed this with your doctor or are not sure why you are taking this medication, speak to your doctor. Do not stop taking this medication without consulting your doctor.
Do not give this medication to anyone else, even if they have the same symptoms as you do. It can be harmful for people to take this medication if their doctor has not prescribed it.
What form(s) does this medication come in?
Each yellow, film-coated, capsule-shaped, biconvex tablet, debossed with "M" on one side of the tablet and "EZ6" on the other side, contains 600 mg of efavirenz. Nonmedicinal ingredients: croscarmellose sodium, microcrystalline cellulose, sodium lauryl sulfate, hydroxypropyl cellulose, lactose monohydrate, and magnesium stearate. Film coating: hypromellose, iron oxide red, iron oxide yellow, polyethylene glycol, and titanium dioxide.
How should I use this medication?
The recommended adult dose of efavirenz is 600 mg once daily taken in combination with other anti-HIV (antiretroviral) drugs. The recommended dose of efavirenz for children age 3 to 17 years of age is based on body weight and will be determined by your doctor.
The efavirenz capsules or tablets should be swallowed whole with a full glass of water. The daily dose is best taken before bedtime to reduce problems associated with potential nervous system side effects.
This medication should ideally be taken on an empty stomach (i.e., 2 hours after a meal). Food can increase how much efavirenz your stomach absorbs, which can increase your risk of side effects.
Your doctor may decide on a different dosing pattern. Do not change your dose unless instructed by your doctor.
Many things can affect the dose of medication that a person needs, such as body weight, other medical conditions, and other medications. If your doctor has recommended a dose different from the ones listed here, do not change the way that you are taking the medication without consulting your doctor.
It is important to take this medication exactly as prescribed by your doctor. If you miss a dose, take it as soon as possible and continue with your regular schedule. If it is almost time for your next dose, skip the missed dose and continue with your regular dosing schedule. Do not take a double dose to make up for a missed one. If you are not sure what to do after missing a dose, contact your doctor or pharmacist for advice.
Store this medication at room temperature, protect it from light and moisture, and keep it out of the reach of children.
Do not dispose of medications in wastewater (e.g. down the sink or in the toilet) or in household garbage. Ask your pharmacist how to dispose of medications that are no longer needed or have expired.
Who should NOT take this medication?
Do not take efavirenz if you:
- are allergic to efavirenz or any ingredients of this medication
- are taking cisapride, midazolam, triazolam, pimozide, St. John's wort, or ergot derivatives
Do not give this medication to children less than 3 years of age or those weighing less than 13 kg.
There are life-threatening interactions that can occur between efavirenz and many other medications. For your safety, if you are thinking about or using any other medication, prescription or non-prescription, you should check with your doctor or pharmacist first. See the "What other medications could interact with this medication?" section for more details.
What side effects are possible with this medication?
Many medications can cause side effects. A side effect is an unwanted response to a medication when it is taken in normal doses. Side effects can be mild or severe, temporary or permanent.
The side effects listed below are not experienced by everyone who takes this medication. If you are concerned about side effects, discuss the risks and benefits of this medication with your doctor.
The following side effects have been reported by at least 1% of people taking this medication. Many of these side effects can be managed, and some may go away on their own over time.
Contact your doctor if you experience these side effects and they are severe or bothersome. Your pharmacist may be able to advise you on managing side effects.
- trouble sleeping
Although most of the side effects listed below don't happen very often, they could lead to serious problems if you do not check with your doctor or seek medical attention.
Check with your doctor as soon as possible if any of the following side effects occur:
- abnormal dreams
- difficulty concentrating
- rash (mild, possibly itchy)
- signs of depression (e.g., poor concentration, changes in weight, changes in sleep, decreased interest in activities, thoughts of suicide)
- signs of infection (symptoms may include fever or chills, severe diarrhea, shortness of breath, prolonged dizziness, headache, stiff neck, weight loss, or listlessness)
- signs of liver problems (e.g., nausea, vomiting, diarrhea, loss of appetite, weight loss, yellowing of the skin or whites of the eyes, dark urine, pale stools)
- signs of pancreatitis (e.g., abdominal pain on the upper left side, back pain, nausea, fever, chills, rapid heartbeat, swollen abdomen)
Stop taking the medication and seek immediate medical attention if any of the following occur:
- signs of a severe skin reaction such as blistering, peeling, a rash covering a large area of the body, a rash that spreads quickly, or a rash combined with fever or discomfort
- thoughts of self-harm
Some people may experience side effects other than those listed. Check with your doctor if you notice any symptom that worries you while you are taking this medication.
Are there any other precautions or warnings for this medication?
Before you begin using a medication, be sure to inform your doctor of any medical conditions or allergies you may have, any medications you are taking, whether you are pregnant or breast-feeding, and any other significant facts about your health. These factors may affect how you should use this medication.
Birth control: Methods of birth control that use hormones, such as a birth control pill, patch or injection, may not be fully reliable as efavirenz interacts with many medications and may change the way that your body uses the hormones. At least 2 forms of non-hormonal birth control (condom, diaphragm) should be used while you are taking this medication. It is recommended that a woman not attempt to become pregnant until at least 12 weeks after stopping this medication, to give the medication time to leave the body.
Depression: Anti-retroviral medications have been known to cause mood swings and symptoms of depression. If you have depression or a history of depression, discuss with your doctor how this medication may affect your medical condition, how your medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed. If you experience symptoms of depression such as poor concentration, changes in weight, changes in sleep, decreased interest in activities, or notice them in a family member who is taking this medication contact your doctor as soon as possible.
Drowsiness/reduced alertness: Side effects of efavirenz may include dizziness, drowsiness, and trouble concentrating. You should not undertake activities requiring mental alertness or physical coordination until you determine that efavirenz does not affect you in this way.
Fat redistribution: Over time, this medication may change how fat is distributed in your body and may change your body shape. You may notice increased fat in the upper back and neck, breast, around the back, chest, and stomach area; or loss of fat from the legs, arms, and face. The long-term effects of this are not known.
Immune reconstitution syndrome: This medication may cause immune reconstitution syndrome, where signs and symptoms of inflammation from previous infections appear. These symptoms occur soon after starting anti-HIV medication and can vary. They are thought to occur as a result of the immune system improving and being able to fight infections that have been present without symptoms (such as pneumonia, herpes or tuberculosis). Report any new symptoms to your doctor immediately.
Liver function: If you have liver problems, discuss with your doctor how this medication may affect your medical condition, how your medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed. Your doctor may want to test your liver function regularly with blood tests while you are taking this medication.
If you experience symptoms of liver problems such as fatigue, feeling unwell, loss of appetite, nausea, yellowing of the skin or whites of the eyes, dark urine, pale stools, abdominal pain or swelling, and itchy skin, contact your doctor immediately.
Pancreatitis: Efavirenz can cause the pancreas to become inflamed. If you have a history of pancreatitis, discuss with your doctor how this medication may affect your medical condition, how your medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed.
Report signs of pancreatitis such as abdominal pain on the upper left side, back pain, nausea, fever, chills, rapid heartbeat, or swollen abdomen to your doctor immediately.
If you have a history of pancreatitis, gallstones, alcoholism, or high triglycerides, you may be more at risk of experiencing this.
Seizures: There have been occasional reports of seizures occurring when taking efavirenz. If you have a history of epilepsy or medical conditions that increase the risk of seizures, discuss with your doctor how this medication may affect your medical condition, how your medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed.
Stopping the medication: If you stop taking this medication, your HIV infection could get worse. Take the medication exactly as prescribed by your doctor, and do not stop taking the medication without checking with your doctor first.
Pregnancy: Women should avoid becoming pregnant while taking efavirenz as this medication may cause harm to a developing baby if it is taken during the first trimester of pregnancy. Your doctor should test you for pregnancy before starting this medication. If you become pregnant while taking this medication, talk with your doctor before stopping the medication. After assessing the risks and benefits of efavirenz in your particular situation, your doctor may recommend that you continue the medication.
Breast-feeding: It is not known if efavirenz passes into breast milk. Women who have HIV infection are cautioned against breast-feeding because of the risk of passing HIV to a baby who does not have the infection.
Children: The safety and effectiveness of using this medication have not been established for children less than 3 years of age or weighing less than 13 kg.
What other drugs could interact with this medication?
There may be an interaction between efavirenz and any of the following:
If you are taking any of these medications, speak with your doctor or pharmacist. Depending on your specific circumstances, your doctor may want you to:
- stop taking one of the medications,
- change one of the medications to another,
- change how you are taking one or both of the medications, or
- leave everything as is.
An interaction between two medications does not always mean that you must stop taking one of them. Speak to your doctor about how any drug interactions are being managed or should be managed.
Medications other than those listed above may interact with this medication. Tell your doctor or prescriber about all prescription, over-the-counter (non-prescription), and herbal medications you are taking. Also tell them about any supplements you take. Since caffeine, alcohol, the nicotine from cigarettes, or street drugs can affect the action of many medications, you should let your prescriber know if you use them.