Side Effect

Cause

·Anaemia

Deficiency of red blood cells due to methotrexate preventing bone marrow cells needed from replicating.

·Fatigue

Fewer red blood cells causing less oxygen to be transported around the body lowering energy levels.

· Bruising, internal bleeding, red spots   on arms or legs, bleeding gums

Fewer platelets, needed to clot the blood due to lower bone marrow function.

· Immunosuppression (leading to increased risk of infection)

Lower bone marrow function lowering white blood cell count, weakening the immune system.

·Diarrhoea

·Vomiting

·Stomach pains

Methotrexate prevents cell reproduction in the lining of the stomach, which can cause all of these three side effects.

·Blood in urine, faeces or vomit.

Caused by gastrointestinal perforation due to prevention of replication of cells of lining of GI tract.

·Change of skin tone

·Increased photosensitivity (sensitivity to sun light)

·Skin irritation.

The drug interferes with melanin production, which produces pigmentation of skin. Skin tone often becomes lighter, but darkening and rashes can also occur.

· Lung problems e.g. pulmonary edema and pleuritic chest pain

Methotrexate affects reproduction of lung cells, which can impair breathing and cause coughing.

·Toxic neuropathy (kidney damage)

In high doses high toxicity of methotrexate can damage kidneys as they try to remove methotrexate from the body.

·Alopecia (hair loss)

Methotrexate inhibits the production of cells in hair follicles causing loss of hair, eyebrows, eyelashes etc.

·Foetal Defects

Methotrexate interferes with the cell reproduction of the foetus preventing it from forming correctly.