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 Sovaldi. If you are concerned about side effects, discuss the risks and benefits of Sovaldi with your doctor.

The following side effects have been reported by at least 1% of people taking Sovaldi. 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.

• headache
• irritability
• nausea
• rash
• tiredness
• 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:

• signs of Anemia (low red blood cells; e.g., dizziness, pale skin, unusual tiredness or weakness, shortness of breath)
• signs of clotting problems (e.g., unusual nosebleeds, bruising, blood in urine, coughing blood, bleeding gums, cuts that don't stop bleeding)
• 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)
• symptoms of very slow heart rate (e.g., dizziness, fainting, feeling unwell, shortness of breath, confusion, memory problems, chest pains, feeling weak or very tired)

Stop taking the medication and seek immediate medical attention if any of the following occur:

• signs of bleeding in the stomach (e.g., bloody, black, or tarry stools; spitting up of blood; vomiting blood or material that looks like coffee grounds)

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 Sovaldi.

Each yellow, capsule-shaped, film-coated, tablet debossed with "GSI" on one side and "7977" on the other side contains 400 mg of sofosbuvir. Nonmedicinal ingredients: mannitol, microcrystalline cellulose, croscarmellose sodium, colloidal silicon dioxide, and magnesium stearate. Film-coating: polyvinyl alcohol, titanium dioxide, polyethylene glycol/macrogol, talc, and yellow iron oxide.

Do not take sofosbuvir if you:

• are allergic to sofosbuvir or any ingredients of the medication
• have any reason that you should not take ribavirin or interferon
• are pregnant or may become pregnant
• have a pregnant partner or a partner who may become pregnant

There may be an interaction between sofosbuvir and any of the following:

• Amiodarone
• "azole" antifungals (e.g., itraconazole, ketoconazole, Voriconazole)
• Carbamazepine
• Carvedilol
• Cyclosporine
• Dronedarone
• HIV protease inhibitors (e.g., atazanavir, indinavir, ritonavir, saquinavir)
• Ivacaftor
• Lapatinib
• macrolide antibiotics (e.g., clarithromycin, erythromycin)
• Modafinil
• Oxcarbazepine
• Phenytoin
• Phenobarbital
• primidone
• quinidine
• quinine
• rifabutin
• rifampin
• rifapentine
• St. John's wort
• Verapamil
• Warfarin

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 Sovaldi. 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.

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 Sovaldi.

Heart function: Taking sofosbuvir while taking certain medications to control heart rhythm may result in a serious decrease in the heart rate. This can cause severe heart problems, including fatal Heart Attack. If you have a history of heart disease or are taking medications to control blood pressure, discuss with your doctor how Sovaldi may affect your medical condition, how your medical condition may affect the dosing and effectiveness of this mediation, and whether any special monitoring is needed.

Hepatitis B reactivation: People who have hepatitis B infection that is dormant may experience the infection returning, causing further liver dysfunction or liver failure. If you have a history of hepatitis B infection, discuss with your doctor how Sovaldi may affect your medical condition, how your medical condition may affect the dosing and effectiveness of this mediation, and whether any special monitoring is needed.

If you experience symptoms of worsening liver function, 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.

Pregnancy and contraception: The use of Sovaldi is not recommended for pregnant women or women who may become pregnant, as other medications which must be taken with sofosbuvir (in particular ribavirin) may cause birth defects or the death of the fetus if it is used during pregnancy. Do not use Sovaldi if you are pregnant or if your partner is pregnant.

Two forms of effective birth control (one for each partner) must be used during treatment and for 6 months after stopping therapy. During this time, women will have monthly pregnancy tests to ensure they are not pregnant. Tell your doctor immediately if you or your partner becomes pregnant while using Sovaldi.

Breast-feeding: It is not known if sofosbuvir passes into breast milk. Due to the potential for serious harm to a baby if they are exposed to these medications, breast-feeding must be stopped before starting Sovaldi.

Children: The safety and effectiveness of using Sovaldi have not been established for children.