Published: 3 June 2021
Publications
Colchicine: painful insights from recent poisoning data in New Zealand
Published: 3 June 2021
Prescriber Update 42(2): 14–16
June 2021
Colchicine indications and dosing1
Colchicine is indicated for the treatment of acute gout when nonsteroidal anti-inflammatory drugs are contraindicated, ineffective or not tolerated.
The approved dose for treatment of acute gout is 1 mg (two tablets) at the first sign of the flare, followed by 0.5 mg (one tablet) one hour later. Higher doses have not been found to be more effective. The maximum recommended dose for treatment of acute gout is 1.5 mg (three tablets) over a one hour period. A course of colchicine should not be repeated within three days.
Some clinical guidelines may refer to unapproved dosing schedules for colchicine. See the Medsafe information about unapproved use of medicines, particularly the requirement for patient consent.
Colchicine can be fatal in overdose
Colchicine has a narrow therapeutic index. The separation between therapeutic and toxic doses is not well defined.2
Case reports and case series data suggest a dose-dependent fatality risk that increases dramatically over a narrow colchicine dose range from 0.5–1 mg/kg when taken over short time periods. Doses well under 0.5 mg/kg (and as low as 0.18 mg/kg) have been associated with deaths in New Zealand, with multiple deaths involving accidental overdoses.3
Fatal colchicine toxicity has occurred in adults at doses as low as 7 mg when taken for a therapeutic purpose.1,2
The risk of toxicity is increased by coadministration with medicines that inhibit cytochrome P450 3A4 or P-glycoprotein, and comorbidities such as renal or hepatic impairment.1
Colchicine toxicity is an extension of its mechanism of action. Colchicine inhibits the formation of microtubules, affecting cell division in all cell types of the body, which accounts for both the therapeutic effects and the multi-organ toxicity seen in colchicine poisoning.2
There is no antidote for colchicine poisoning. Treatment is usually supportive and involves early administration of activated charcoal.1 Colchicine toxicity has a high mortality rate.2
Poisoning from colchicine in New Zealand
From 1 January 2016 to 14 January 2021, the National Poisons Centre (NPC) received 56 unique cases related to colchicine poisoning. Māori and Pacific peoples comprised 34 percent of the poisoning cases, 13 percent were European, and the remainder were of unknown ethnicity.
Forty-three percent of the cases were aged 1 to 4 years, and 36 percent of the cases were aged 20 to 75 years. Table 1 below shows the number of colchicine poisoning incidents per year and the reasons.
The NPC provided the following insights into the poisonings.
- Child exploratory behaviour: 43 percent of all colchicine cases were toddlers and young children (aged 1 to 4 years) gaining unsupervised access to the medicine. Due to the small size of children, as little as one or two tablets may be of concern for toxicity – prompting referral for medical assessment.
- Therapeutic error: 35 percent of cases were adults who were exposed to a supratherapeutic dose. These exposures may be due to patients misunderstanding how to take colchicine appropriately or trying to get further therapeutic effect to ease symptoms of gout.
- Intentional self-poisoning: any intentional exposure to colchicine poses a medical emergency, given the severity of toxicity and high fatality rate associated with colchicine overdose.
Table 1: Number of colchicine poisoning incidents and reasons as reported to the National Poisons Centre, New Zealand, 2016 to 2021a,b
| Reason | Number per year | Total | ||||||
|---|---|---|---|---|---|---|---|---|
| 2016 | 2017 | 2018 | 2019 | 2020 | 2021b | No. | % | |
| Child exploratory behaviour | 3 | 11 | 1 | 4 | 5 | 0 | 24 | 43 |
| Intentional | 1 | 0 | 3 | 2 | 5 | 1 | 12 | 21 |
| Therapeutic error | 1 | 5 | 1 | 3 | 5 | 0 | 15 | 27 |
| Unintentional | 0 | 0 | 0 | 3 | 1 | 0 | 4 | 7 |
| Unknown | 0 | 0 | 0 | 0 | 1 | 0 | 1 | 2 |
| Total | 5 | 16 | 5 | 12 | 17 | 1 | 56 | 100 |
Source: National Poisons Centre
Notes:
- The data does not capture all harmful or potentially harmful colchicine poisonings that occurred during the specified period in New Zealand, as contacting the National Poisons Centre is voluntary.
- Data to 14 January 2021.
Reducing harm from colchicine in the community
- Communicate with patients about the importance of storing medicines out of sight and reach of children.
- Encourage patients to return unused or expired medicines to their local pharmacy for appropriate disposal.
- When dispensing colchicine, discuss with the patient if a child resistant closure would be acceptable, taking into account patient and whānau factors.
- Ensure patients know when and how to take colchicine. Health Navigator is a useful consumer resource, with patient information leaflets about colchicine.
- If a patient experiences colchicine poisoning, contact the National Poisons Centre on 0800 764 766 for consultation with a clinical toxicologist for risk assessment and recommendations on treatment. This service is available 24/7.
More information
See the following Prescriber Update articles about colchicine:
- Spotlight on colchicine – March 2018
- Keeping patients informed about colchicine use – December 2014
- Colchicine: Beware of toxicity and interactions – March 2011.
See also the Medsafe consumer information leaflet, Medicines for gout.
References
- Pharmacy Retailing t/a Healthcare Logistics. 2020. Colgout New Zealand Data Sheet November 2020 URL: medsafe.govt.nz/profs/datasheet/c/Colgouttab.pdf (accessed 30 March 2021).
- Finkelstein Y AS, Hutson JR, Juurlink DN, et al. 2010. Colchicine poisoning: the dark side of an ancient drug. Clinical Toxicology 48(5): 407-14. DOI: https://doi.org/10.3109/15563650.2010.495348 (accessed 30 March 2021).
- Jayaprakash V, Ansell G, Galler D. 2007. Colchicine overdose: the devil is in the detail. New Zealand Medical Journal 120(1248): U2402. PMID: 17277818 (accessed 19 April 2021).
