What is colchicine?
Colchicine is a very old drug and 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 secondline agent when safer drugs have been unsuccessful.
Colchicine for dermatological diseases
Colchicine is used for a number of dermatological diseases. Its effectiveness has only been shown through the treatment of small and mostly uncontrolled study groups.
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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 a 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
- 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 pain killers, 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).
- 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 is possible by reducing the dosage. However, there is no antidote if an excessive dose is taken. Seek medical help immediately.