Symfi Lo is a combination antiviral medicine that is used to treat human immunodeficiency virus (HIV). HIV is the virus that can cause acquired immunodeficiency syndrome (AIDS). Symfi Lo is not a cure for HIV or AIDS.

Symfi is for use in adults and children who weigh at least 88 pounds (40 kilograms).

Symfi Lo is for use in adults and children who weigh at least 77 pounds (35 kilograms).

Symfi Lo may also be used for purposes not listed in this medication guide.

If you've ever had hepatitis B, it may become active or get worse after you stop using this medicine. You may need frequent liver function tests for several months.

Do not change your dose or stop taking this medicine without your doctor's advice.

Follow all directions on your prescription label and read all medication guides or instruction sheets. Use the medicine exactly as directed.

Symfi Lo is a complete regimen and is not for use with other antiviral medications.

Take this medicine on an empty stomach at bedtime.

You will need frequent medical tests.

Do not change your dose or dosing schedule without your doctor's advice. Every person with HIV should remain under the care of a doctor.

Store this medicine in the original container at room temperature, away from moisture and heat.

If you've ever had hepatitis B, this virus may become active or get worse in the months after you stop using this medicine. You may need frequent liver function for several months after your last dose.

You should not use this medicine if:

• you also take elbasvir and grazoprevir (for hepatitis C); or

• you are allergic to any antiviral combination medicine that contains efavirenz, lamivudine, or tenofovir.

Tell your doctor if you have ever had:

• liver disease (especially hepatitis B or C); or

• kidney disease (or if you are on dialysis);

• heart problems;

• long QT syndrome (in you or a family member);

• drug or alcohol addiction;

• a seizure; or

• fractures or other problems with your bones.

You may develop lactic acidosis, a dangerous build-up of lactic acid in your blood. This may be more likely if you are overweight or if you are a woman. Ask your doctor about your risk.

You may need to have a negative pregnancy test before starting this treatment.

Do not use this medicine if you are pregnant. It could harm the unborn baby or cause birth defects. Use effective birth control to prevent pregnancy while you are using this medicine and for at least 12 weeks after your last dose.

Use two forms of birth control to prevent pregnancy, including a barrier form such as a condom, diaphragm, cervical cap, or contraceptive sponge.

If you are pregnant, your name may be listed on a pregnancy registry to track the effects of this medicine on the baby.

Women with HIV or AIDS should not breast feed a baby. Even if your baby is born without HIV, the virus may be passed to the baby in your breast milk.

Take the medicine as soon as you can, but skip the missed dose if it is almost time for your next dose. Do not take two doses at one time.

Get your prescription refilled before you run out of medicine completely.

Seek emergency medical attention or call the Poison Help line at 1-800-222-1222.

Avoid eating or drinking anything that contains sorbitol (an artificial sweetener).

Avoid driving or hazardous activity until you know how this medicine will affect you. Your reactions could be impaired.

Get emergency medical help if you have signs of an allergic reaction (hives, difficult breathing, swelling in your face or throat) or a severe skin reaction (fever, sore throat, burning in your eyes, skin pain, red or purple skin rash that spreads and causes blistering and peeling).

Symfi Lo may cause serious side effects. Call your doctor at once if you have:

• severe dizziness or drowsiness, trouble concentrating, strange dreams;

• confusion, thinking problems, seeing or hearing things that are not real (may occur months to years after you start taking this medicine);

• fast or pounding heartbeats, fluttering in your chest, and sudden dizziness (like you might pass out);

• problems with balance or coordination;

• new or worsening bone pain;

• pain in your arms, legs, hands, or feet;

• lactic acidosis--unusual muscle pain, trouble breathing, stomach pain, vomiting, irregular heart rate, dizziness, feeling cold, or feeling very weak or tired;

• pancreatitis--severe pain in your upper stomach spreading to your back, nausea and vomiting;

• unusual thoughts--fear, paranoia, feeling sad or hopeless, thoughts of hurting yourself or others; or

• liver problems--swelling around your midsection, upper stomach pain, unusual tiredness, loss of appetite, dark urine, clay-colored stools, jaundice (yellowing of the skin or eyes).

Symfi affects your immune system, which may cause certain side effects (even weeks or months after you've taken this medicine). Tell your doctor if you have:

• signs of a new infection--fever, night sweats, swollen glands, cold sores, cough, wheezing, diarrhea, weight loss;

• trouble speaking or swallowing, problems with balance or eye movement, weakness or prickly feeling; or

• swelling in your neck or throat (enlarged thyroid), menstrual changes, impotence.

Common side effects of Symfi Lo may include:

• headache, dizziness;

• depression, thinking problems;

• nausea, diarrhea;

• sleep problems (insomnia);

• pain;

• weakness, tiredness;

• cough, stuffy nose, sinus pain;

• rash; or

• changes in the shape or location of body fat (especially in your arms, legs, face, neck, breasts, and waist).

This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.

Sometimes it is not safe to use certain medications at the same time. Some drugs can affect your blood levels of other drugs you take, which may increase side effects or make the medications less effective.

Many drugs can affect Symfi Lo. This includes prescription and over-the-counter medicines, vitamins, and herbal products. Not all possible interactions are listed here. Tell your doctor about all your current medicines and any medicine you start or stop using.