Colchicine

What is colchicine?

Colchicine is an ancient drug is made from the Autumn Crocus, Colchicum autumnale (a poisonous European flowering plant). It has been primarily used in the treatment of gout. Although it is not formally indicated or approved for the treatment of dermatological diseases, colchicine has been prescribed for some skin conditions with good results. Its effectiveness is due to several immunological and anti-inflammatory properties.

In New Zealand colchicine is available as 0.5 mg (or 500 micrograms) tablets (previously 0.6 mg).

Because of its potential toxicity, colchicine is used as a second line agent when safer drugs have been unsuccessful.

Colchicine for dermatological diseases

Colchicine is used for some dermatological diseases. Its effectiveness has only been shown through the treatment of small and mostly uncontrolled study groups.

Other dermatological conditions that may be treated with colchicine include linear IgA dermatosis, acquired epidermolysis bullosa, vasculitis, morphoea and dermatomyositis.

More controlled and double-blind studies are needed to prove the usefulness of colchicine in dermatological diseases.

Contraindications to colchicine

Colchicine should not be used under the following circumstances:

• Patients with known hypersensitivity (allergy) to the medicine
• Patients with serious gastrointestinal, kidney, liver or heart disorders
• Patients with blood diseases in which there are low numbers of white cells or platelets
• Patients taking statins (cholesterol-lowering medications)
• Pregnant women

Precautions when using colchicine

Colchicine can be fatal in overdose. Treatment with colchicine should be stopped immediately when abdominal pain, diarrhoea, nausea or vomiting occur. These are the first signs of toxicity and usually occur between 0–24 hours after taking the medicine.

If you are taking any other medicines, particularly antibiotics and painkillers, do not take colchicine before you have checked with your doctor or pharmacist that it is safe to do so.

Side effects of colchicine

The most common side effects are abdominal pain, diarrhoea, nausea or vomiting, which occur in up to 80% of patients receiving a maximal dose. Gastrointestinal symptoms are worse at higher dosages. These symptoms indicate toxicity and the medicine should be stopped.

Toxicity results in:

• Bone marrow depression resulting in agranulocytosis (absent white blood cells) and thrombocytopenia (low numbers of platelets)
• Peripheral neuritis (nerve inflammation affecting hands and feet)
• Purpura (bleeding into the skin)
• Myopathy (weak muscles)
• Loss of hair
• Azoospermia (absent sperm production).
• Seizures
• Cardiac arrhythmia (palpitations) and low blood pressure
• Lung, kidney and liver failure

Colchicine, when used in low doses, has a low rate of side effects. Beneficial effects without the side effects are possible by reducing the dosage. However, there is no antidote if an excessive dose is taken. Seek medical help immediately.