The potential for error in prescribing and dispensing alfacalcidol drops (One-Alpha) has been highlighted this week. In a letter from Dr Pat Troop (deputy chief medical officer) and Mrs Jeannette Howe (acting chief pharmacist), health professionals, including pharmacists, are asked to be aware of a potential problem that has arisen following a change in formulation.
A high-strength formulation of alfacalcidol, One-Alpha drops, was launched in July, 2000. This formulation is 10 times stronger than the former presentation, One-Alpha solution, which was discontinued in September, this year. The letter states: "If a prescription for alfacalcidol is written in mls rather than µg, there is potential for a patient to be given a dose 10 times that intended. "
The Medicines Control Agency has advised doctors and pharmacists to be vigilant when prescribing, dispensing and administering alfacalcidol drops. It adds that doses should be given in µg and that any suspected adverse reaction to alfacalcidol, including overdoses, should be reported through the yellow card scheme.
The most recent edition of the British National Formulary (number 40, September, 2000) states that the strength of alfacalcidol drops is 2µg/ml and includes a sentence noting that the concentration of One-Alpha drops is 10 times stronger than that of the former presentation One-Alpha solution. Professor Martin Kendall (chairman of the BNF's joint formulary committee) said in a recent press statement: "Alfacalcidol is a potent drug of considerable value in conditions such as severe renal impairment, but it can have serious consequences in overdose. As such, prescribers and pharmacists should take great care to use the most up-to-date and reliable source of prescribing information and should ensure that they are familiar with the BNF's guidance on prescription writing. "