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 3tc. If you are concerned about side effects, discuss the risks and benefits of 3tc with your doctor.

The following side effects have been reported by at least 1% of people taking 3tc. 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.

• abdominal or stomach pain
• Diarrhea
• Fever
• general feeling of being unwell
• headache
• nausea
• rash
• tiredness
• vomiting

Although most of these side effects listed below don't happen very often, they could lead to serious problems if you do not seek medical attention.

Check with your doctor as soon as possible if any of the following side effects occur:

• severe muscle pain or cramping
• signs of Anemia (low red blood cells; e.g., dizziness,  pale skin, unusual tiredness or weakness, shortness of breath)
• signs of poor blood clotting (e.g., unusual nosebleeds, bruising, blood in urine, coughing blood, bleeding gums, cuts that don't stop bleeding)
• signs of an autoimmune disorder (e.g., high fever, joint pain, swelling, rash, unusual fatigue)
• symptoms of ear, nose, or throat infection such as fever, chills, cough, or sore throat
• symptoms of liver problems (e.g., nausea, vomiting, abdominal pain, weakness, diarrhea)
• tingling; burning; numbness; or pain in the hands, arms, feet, or legs
• unusual tiredness or weakness

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

• symptoms of a Anaphylaxis (severe allergic reaction) (e.g., swelling of the eyes, face, lips, throat, sudden wheezing, Hives)
• symptoms of lactic acidosis (e.g., weight loss, fatigue, nausea, vomiting, abdominal pain, shortness of breath, generally feeling unwell)
• signs of pancreatitis (e.g., abdominal pain on the upper left side, back pain, chills, fever, nausea, rapid heartbeat, swollen abdomen)

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 3tc.

Oral solution

Each mL of colourless-to-pale-yellow, strawberry-banana-flavoured, clear liquid contains 10 mg of lamivudine. Nonmedicinal ingredients: artificial strawberry and banana flavours, citric acid (anhydrous), hydrochloric acid, methylparaben, propylene glycol, propylparaben, sodium citrate (dihydrate), sodium hydroxide, sucrose, and water. Each 150 mg (15 mL) contains 3 g of sucrose.

Tablets

150 mg
Each, white, modified-diamond-shaped, film-coated tablet imprinted with "GX CJ7" on one face contains 150 mg of lamivudine. Nonmedicinal ingredients: hydroxypropyl methylcellulose, magnesium stearate, microcrystalline cellulose, polyethylene glycol, polysorbate 80, sodium starch glycolate, and titanium dioxide.

300 mg
Each grey, modified-diamond-shaped, film-coated tablet imprinted with "GX EJ7" on one face contains 300 mg of lamivudine. Nonmedicinal ingredients: black iron oxide, hydroxypropyl methylcellulose, magnesium stearate, microcrystalline cellulose, polyethylene glycol, polysorbate 80, sodium starch glycolate, and titanium dioxide.

Do not take lamivudine if you are allergic to lamivudine or any of the ingredients of the medication.

Do not give 3tc to children less than 3 months old.

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

• Cabozantinib
• Cladribine
• co-trimoxazole (sulfamethoxazole/trimethoprim)
• emtricitabine
• Orlistat
• sorbitol
• Trimethoprim

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 3tc. 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 3tc.

Diabetes: People with diabetes need to know that an adult dose of the oral (by mouth) solution of lamivudine contains 3 g of sucrose.

Hepatitis B: For people with hepatitis B, your doctor will talk to you about HIV treatment before you begin taking lamivudine. If you have not been tested already, your doctor will suggest that you be tested for hepatitis B before starting 3tc. People with HIV and hepatitis B who stop taking lamivudine may experience a recurrence of hepatitis B.

Immune reconstitution inflammatory syndrome: 3tc 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.

Kidney function: Kidney Disease or reduced kidney function may cause 3tc to build up in the body, causing side effects. People with reduced kidney function may need a lower dose of the medication. If you have kidney disease or decreased kidney function, discuss with your doctor how 3tc may affect your medical condition, how your medical condition may affect the dosing and effectiveness of 3tc, and whether any special monitoring is needed.

Lactic acid and enlarged liver: Lamivudine can cause a rare, but serious condition called lactic acidosis (buildup of lactic acid in the blood) together with an enlarged liver. If you experience weight loss, fatigue, nausea, vomiting, abdominal pain, shortness of breath, generally feeling unwell, weakness, or diarrhea, contact your doctor immediately. Your doctor will monitor your liver function periodically by ordering laboratory tests.

Pancreatitis: Lamivudine may cause pancreatitis (inflammation of the pancreas). If you develop abdominal pain, nausea, or vomiting while taking 3tc, contact your doctor immediately.

Parents of children who have received anti-HIV medications in the past, have a history of or are at risk of pancreatitis should discuss with their child's doctor how 3tc may affect their medical condition, how their medical condition may affect the dosing and effectiveness of 3tc, and whether any special monitoring is needed.

Red blood cells: Pure red cell aplasia is a rare bone marrow disorder characterized by a reduction in red blood cells produced by the bone marrow. Symptoms include pallor, weakness, shortness of breath, heart palpitations, and decreased blood pressure. Be sure to contact your doctor immediately if you experience any of these symptoms.

Pregnancy: 3tc should not be used during pregnancy unless the benefits outweigh the risks. If you become pregnant while taking 3tc, contact your doctor immediately.

Breast-feeding: 3tc passes into breast milk. If you are a breast-feeding mother and are taking lamivudine, it may affect your baby. 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 lamivudine have not been established for children less than 3 months of age.