One in 20 prescriptions written by GPs in England contains an error, and one in 550 contains a serious error, a large study has found.

The prevalence and causes of prescribing errors in general practice study, commissioned by the General Medical Council, shows that it is not doctors’ knowledge about drugs that is responsible for most errors but human factors and process issues. Errors chiefly occur because of problems in the process of prescribing and failure to monitor and review patients adequately.

Pharmacists reviewed 6048 prescriptions written for 1777 patients by GPs at 15 general practices in England for errors. Most of the 247 prescribing errors and 55 monitoring errors identified were not serious: 42% were minor, 54% moderate, and 4% severe. The most serious related to failure to adequately monitor warfarin or to prescribe a drug to a patient with a documented allergy to it—the two cases of allergy that occurred involved penicillin and …