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Dosing error

01 August 2004

Mr and Mrs F were due to travel to East Africa in the late 1990s. They consulted their GP, Dr L, for advice on appropriate travel prophylaxis. Dr L immunised them against yellow fever and recommended anti-malarial prophylaxis with mefloquine.

Mrs F had some concerns about the side-effects of mefloquine, which she discussed with Dr L. Dr L felt that mefloquine, despite potential side-effects, was the best agent for them to use.

Dr L prescribed mefloquine 250mg once daily, for both Mr and Mrs F. Dr L advised them to start taking one tablet daily until departure, one daily whilst away and one daily for a month after their return.

Mefloquine is normally prescribed on a once-weekly basis. The tablets were dispensed by a local pharmacist and labelled ‘Mefloquine tablets 250mg, take one every day.’

Mr and Mrs F became unwell on arrival at their destination. Their travel representative pointed out the apparent error in the dose of their mefloquine. They suffered arthralgia, abdominal pain, chronic diarrhoea, vomiting, dizziness, ataxia, headaches, acute anxiety and depression.

Their psychiatric symptoms persisted in the long term.

Mr and Mrs F attempted to return to work, but found that their psychiatric symptoms prevented them from doing so.

We settled the case, sharing liability with the pharmacist. The settlement awarded to Mr and Mrs F reflected their loss of earnings.

Learning points

Anyone can make a mistake, but mistakes in the area of prescribing can have serious consequences. When prescribing a medication with which you are not familiar, it is wise to check the dosing regimen in a formulary before doing so.

Computerised prescribing systems are useful to highlight medications with unusual dosing regimens, such as mefloquine or methotrexate, which are usually given on a weekly basis.

Incorporating a ‘failsafe’ in prescribing systems, so that a clinician cannot prescribe a larger-than-recommended dose of a drug without overriding an automated warning, is a useful risk-management tool.

A system to flag-up an unorthodox dosing regimen, requiring clarification with the prescriber, would have been useful in this case.

There are many software providers who incorporate such systems in their products, and it’s worth checking out the availability of such features when buying/renewing pharmacy-dispensing software.

A study in secondary care has shown the usefulness and popularity of such a system. See Nightingale PG et al. ‘Implementation of a Rules Based Computerised Bedside Prescribing and Administration System: Intervention Study’, BMJ, 320:750-3 (2000).

In the UK the Department of Health has produced a document, Building a Safer NHS for Patients: Improving Medication Safety, which can be found on the Department of Health website,