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 Lanvis (Thioguanine). If you are concerned about side effects, discuss the risks and benefits of Lanvis (Thioguanine) with your doctor.

The following side effects have been reported by at least 1% of people taking Lanvis (Thioguanine). 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.

• Diarrhea
• loss of appetite
• nausea and vomiting
• skin rash and itching

Although most of the 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:

• joint pain
• sores in the mouth or on the lips
• signs of Anemia (low red blood cells; e.g., dizziness, pale skin, unusual tiredness or weakness, shortness of breath)
• signs of bleeding (e.g., bloody nose, blood in urine, coughing blood, bleeding gums, cuts that don't stop bleeding)
• signs of infection (Fever, severe chills, sore throat, mouth ulcers)
• signs of abnormal liver function including skin or whites of the eyes turning yellow, feeling tired, dark or brown coloured urine, nausea or vomiting or not wanting to eat)
• swelling of the feet or lower legs
• unsteadiness when walking

Contact your doctor immediately if any of the following side effects 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)
• signs of a serious allergic reaction (e.g., abdominal cramps, difficulty breathing, nausea and vomiting, or swelling of the face and throat)

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 Lanvis (Thioguanine).

Each pale, greenish-yellow, biconvex tablet, plain on one side and scored on the other side with "Wellcome" on the upper half and "U3B" on the lower half, contains 40 mg of Lanvis (Thioguanine). Nonmedicinal ingredients: gum acacia, lactose, magnesium stearate, potato starch, and stearic acid.

Do not take Lanvis (Thioguanine) if you:

• are allergic to Lanvis (Thioguanine) or any ingredients of Lanvis (Thioguanine)
• have been resistant to the effects of Lanvis (Thioguanine) or Mercaptopurine in the past

There may be an interaction between Lanvis (Thioguanine) and any of the following:

• aminosalicylate drugs (e.g., Sulfasalazine, mesalazine, Olsalazine)
• bacillus Calmette-Guérin (BCG)
• Deferiprone
• Denosumab
• dipyrone
• echinacea
• Fingolimod
• Leflunomide
• Natalizumab
• other cancer medications
• Pimecrolimus
• Roflumilast
• Tacrolimus
• Tofacitinib
• vaccines

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 Lanvis (Thioguanine). 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 Lanvis (Thioguanine).

Anemia: Lanvis (Thioguanine) may cause low levels of red blood cells. If you experience symptoms of reduced red blood cell count (anemia) such as shortness of breath, feeling unusually tired, or pale skin, contact your doctor as soon as possible

Blood clotting: Lanvis (Thioguanine) can reduce the number of platelet cells in the blood. Platelets help the blood to clot, and a shortage could make you bleed more easily. Tell your doctor of any signs that your blood is not clotting as quickly as usual. Such symptoms may include black and tarry stools, blood in the urine, easy bruising, or cuts that won't stop bleeding.

Gout: Lanvis (Thioguanine) increases the blood levels of uric acid, which may increase the risk of gout.

Infection: As well as killing cancer cells, Lanvis (Thioguanine) can reduce the number of cells that fight infection in the body (white blood cells). Avoid contact with people with contagious infections and tell your doctor if you begin to notice signs of an infection, such as fever or chills.

Liver function: Lanvis (Thioguanine) can reduce liver function and can cause liver damage. If you have liver problems, discuss with your doctor how Lanvis (Thioguanine) may affect your medical condition, how your medical condition may affect the dosing and effectiveness of Lanvis (Thioguanine), and whether any special monitoring is needed. Your doctor will order blood tests for your liver function regularly while you are taking Lanvis (Thioguanine).

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.

Pregnancy: There is a possibility of birth defect if either the man or woman is using Lanvis (Thioguanine) at the time of conception. As well, it may harm the baby if used during pregnancy. Effective birth control should be practiced while using Lanvis (Thioguanine).

Lanvis (Thioguanine) should not be used during pregnancy unless the benefits outweigh the risks. If you become pregnant while taking Lanvis (Thioguanine), contact your doctor immediately.

Breast-feeding: It is not known whether Lanvis (Thioguanine) passes into breast milk. Because of the risks associated with Lanvis (Thioguanine), a decision should be made to stop breast-feeding or to stop the medication, taking into account the importance of the medication to the mother.