SIDE EFFECTS: Nausea may occur. If this effect persists or worsens, tell your doctor or pharmacist promptly. Remember that your doctor has prescribed this medication because he or she has judged that the benefit to you is greater than the risk of side effects. Many people using this medication do not have serious side effects. As your immune system gets stronger, it can begin to fight off infections you already had, possibly causing disease symptoms to come back. You could also have symptoms if your immune system becomes overactive. This reaction may happen at any time (soon after starting HIV treatment or many months later). Get medical help right away if you have any serious symptoms, including: unexplained weight loss, severe tiredness, muscle aches/weakness that doesn't go away, headaches that are severe or don't go away, joint pain, numbness/tingling of the hands/feet/arms/legs, vision changes, signs of infection (such as fever, chills, swollen lymph nodes, trouble breathing, cough, non-healing skin sores), signs of an overactive thyroid (such as irritability, nervousness, heat intolerance, fast/pounding/irregular heartbeat, bulging eyes, unusual growth in the neck/thyroid known as a goiter), signs of a certain nerve problem known as Guillain-Barre syndrome (such as trouble breathing/swallowing/moving your eyes, drooping face, paralysis, trouble speaking). Tell your doctor right away if you have any serious side effects, including: yellowing eyes/skin, persistent nausea/vomiting, loss of appetite, stomach/abdominal pain, dark urine, increased thirst/urination, dizziness, lightheadedness, signs of kidney problems (such as pain in side/back/abdomen, painful urination, blood in the urine, change in the amount of urine). Get medical help right away if you have any very serious side effects, including: signs of a heart attack (such as chest/jaw/left arm pain, shortness of breath, unusual sweating). Changes in body fat may occur while you are taking this medication (such as increased fat in the upper back and stomach areas, decreased fat in the arms and legs). The cause and long-term effects of these changes are unknown. Discuss the risks and benefits of treatment with your doctor, as well as the possible use of exercise to reduce this side effect. This medication can commonly cause a rash that is usually not serious. However, you may not be able to tell it apart from a rare rash that could be a sign of a severe reaction. Therefore, get medical help right away if you develop any rash. A very serious allergic reaction to this drug is rare. However, get medical help right away if you notice any symptoms of a serious allergic reaction, including: rash, itching/swelling (especially of the face/tongue/throat), severe dizziness, trouble breathing. This is not a complete list of possible side effects. If you notice other effects not listed above, contact your doctor or pharmacist. In the US - Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088 or at www.fda.gov/medwatch. In Canada - Call your doctor for medical advice about side effects. You may report side effects to Health Canada at 1-866-234-2345.

PRECAUTIONS: Before taking atazanavir/cobicistat, tell your doctor or pharmacist if you are allergic to atazanavir; or to cobicistat; or if you have any other allergies. This product may contain inactive ingredients, which can cause allergic reactions or other problems. Talk to your pharmacist for more details. Before using this medication, tell your doctor or pharmacist your medical history, especially of: liver problems (including hepatitis B or C infections), kidney problems (including kidney stones), heart problems (such as heart rhythm problems, irregular heartbeat, coronary artery disease, heart attack), a certain bleeding problem (hemophilia). This medication may increase the level of cholesterol and fats (triglycerides) in your blood. HIV infection can also cause this effect. This could increase your risk for heart problems such as a heart attack. Discuss the risks and benefits of treatment with your doctor and ways to lower your risk of heart disease. Tell your doctor if you have heart problems, if you smoke, or if you have other conditions that increase your risk of heart disease such as high blood pressure, diabetes, or high cholesterol/triglyceride levels. Before having surgery, tell your doctor or dentist about all the products you use (including prescription drugs, nonprescription drugs, and herbal products). During pregnancy, this medication should be used only when clearly needed. Treatment can lower the risk of passing HIV infection to your baby, and atazanavir/cobicistat may be part of that treatment. Discuss the risks and benefits with your doctor. Atazanavir passes into breast milk. It is unknown if cobicistat passes into breast milk. Because breast milk can transmit HIV, do not breast-feed.

DRUG INTERACTIONS: See also How to Use section. Drug interactions may change how your medications work or increase your risk for serious side effects. This document does not contain all possible drug interactions. Keep a list of all the products you use (including prescription/nonprescription drugs and herbal products) and share it with your doctor and pharmacist. Do not start, stop, or change the dosage of any medicines without your doctor's approval. Some products that may interact with this drug include: drospirenone/estradiol, elvitegravir, certain medications used to treat chronic hepatitis C (such as boceprevir, simeprevir, elbasvir/grazoprevir), indinavir, orlistat, ritonavir. This medication can slow down the removal of other medications from your body, which may affect how they work. Examples of affected drugs include certain alpha blockers (such as alfuzosin, silodosin), certain benzodiazepines (midazolam, triazolam), dronedarone, ergot alkaloids (such as dihydroergotamine, ergotamine), irinotecan, lurasidone, pimozide, certain drugs to treat erectile dysfunction-ED or pulmonary hypertension (avanafil, sildenafil), certain "statin" cholesterol drugs (lovastatin, simvastatin), salmeterol, among others. Other medications can affect the removal of this medication from your body, which may affect how this medication works. Examples include certain HIV NNRTIs (such as efavirenz, etravirine, nevirapine), certain rifamycins (such as rifampin, rifapentine), certain drugs used to treat seizures (such as carbamazepine, phenobarbital, phenytoin, primidone), St. John's wort, among others. Prescription and nonprescription drugs to treat heartburn, indigestion, or ulcers (including H2 blockers such as famotidine, proton pump inhibitors such as lansoprazole/omeprazole) reduce stomach acid and decrease the absorption of atazanavir. This may prevent atazanavir from working well. Ask your doctor or pharmacist how to use these medications safely. This medication may decrease the effectiveness of hormonal birth control such as pills, patch, or ring. This could cause pregnancy. Talk to your doctor about additional or alternative reliable forms of birth control, and always use an effective barrier method (latex or polyurethane condoms/dental dams) during all sexual activity to decrease the risk of spreading HIV to others. Tell your doctor if you have any new spotting or breakthrough bleeding, because these may be signs that your hormonal birth control is not working well. Do not use this medication with other products that contain atazanavir or cobicistat.

OVERDOSE: If someone has overdosed and has serious symptoms such as passing out or trouble breathing, call 911. Otherwise, call a poison control center right away. US residents can call their local poison control center at 1-800-222-1222. Canada residents can call a provincial poison control center. Symptoms of overdose may include: severe dizziness, lightheadedness.