Objective To quantify what proportion of prescribed doses of liquid medicine for children and neonates were measurable.

Method Prescriptions for liquid medicine for inpatients were reviewed over five weeks at two hospitals in the North West of England in January/February 2011. Patients on Neonatal and Paediatric Intensive Care units and children's wards were considered for study. Date of birth, name, strength and prescribed dose of drug, the volume to be administered and whether that dose was measurable using a single syringe were documented. The volume required to administer each dose was calculated from the prescribed dose using the concentration of the formulation available on the ward. A dose was considered measurable if the volume required could be measured using the smallest single syringe. Analysis of the data by SPSS involved frequency statistics.

Results 1599 liquid doses for 431 patient records were reviewed. 196 liquid doses (12.3%) were immeasurable. Of these immeasurable doses, 29 (14.8%) related to neonates, 58 to infants (25.6%), 81 to children (41.3%) and 28 to adolescents (14.3%). Syringes used for immeasurable doses ranged from 1 ml to 60 ml, 1 ml syringe accounting for 25% (49/192) immeasurable doses; 2.5 ml syringe 28.6% (55/196), 5 ml syringe 22.5% (44/196), 10 ml syringe 16.8% (33/196) and syringes ≥20 ml 7.7% (15/196). Medicines that were deemed immeasurable included those for infection (eg, cefradine, ceftazidime, gentamicin, metronidazole) 34.2% (67/192) and analgesia (eg, paracetamol, ibuprofen and diclofenac) accounted for 25% (49/196). Others medicines included antiepileptics (3.6%, 7/196) for example phenytoin and phenobarbital; corticosteroids (10.7%, 21/196) for example dexamethasone and hydrocortisone; GI medicines (9.2%, 18/196) for example rantidine, domperidone and ondansetron and sedatives (5.1%, 10/196) for example chloral hydrate and diazepam.

Conclusion The study found that one in eight prescribed doses of liquid medicine for children and neonates cannot physically be measured. The measurability of prescribed doses of medicine must be addressed. Ideally this consideration should take place at the time of prescribing or be reviewed by the pharmacist prior to administering the first dose. Resolving the widespread problem of immeasurable doses is complicated by the fact that concentrations of medicine vary widely. For example 24 mg of paracetamol liquid is sensible and can be measured. However 5 mg of dexamethasone is immeasurable and would better be prescribed as 4.95 mg? Further research to explore the measurability of doses of liquid medicines and the relationship with medicines that have a narrow therapeutic window should be undertaken.