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Re: Children's Doses Should be Measurable

Dear Sir

We read with interest the suggestion that dosing charts may reduce gentamicin prescribing errors.(1)

We fully support the concept but raise question with some of the detail.

BNFc advises against use of unecessary decimal points.(2) They may be misinterpreted or misread and result in 10-fold overdose.(3) Doses in the neonatal table include trailing zero’s. We would suggest that the information presented should accurately refelect exactly what the clinician should prescribe, or nurse administer.

We also question the need for overly precise doses that cannot physically be administered.

All injectable medicines should be administered in a single syringe. Syringes enable: • doses of less than 1ml to be measured to the nearest 0.01ml • doses of 1 to 2.5ml to be measured to the nearest 0.1ml and • doses of 2.5 to 5ml to be measured to the nearest 0.2ml. We therefore question recommendations to prescribe and thus administer doses of 238mg (34kg child) or 11.6mg (2.9kg child). Gentamicin injection is a 10mg/ml or 40mg/ml solution. 238mg is a dose volume of 5.95ml. 11.6mg is a dose volume of 1.16ml. Neither can be measured accurately. We would advise that dose rounding is applied to the tables so that 238mg becomes 240mg and 11.6mg becomes 12mg.

We recently performed a point prevalence study of medicines administered to neonates within the level three neonatal unit at Wirral Hospitals over three non-consecutive days. Of 261 administered medicines, 31 doses were different from the prescribed amount because the nurse had to approximate the dose. These included doses of potent medicines including tazocin and phenytoin. We plan to repeat the study in all neonatal units within the Cheshire and Mersey Neonatal Network to quantify the extent of dose approximation.

In our opinion doses that are prescribed for children and neonates should be precise, accurate, appropriate and be physically possible to administer. Nursing staff should never have to guess an approximate dose.

Yours faithfully

Neil A. Caldwell Consultant Pharmacist, Children’s Services/Honorary Lecturer Wirral University Teaching Hospitals NHS Foundation Trust/Liverpool John Moores University

Oliver Rackham Consultant Paediatrician Wirral University Teaching Hospitals NHS Foundation Trust