PHARMACY MEDICINES RISK MANAGEMENT BRIEFING NOTE
No 50
Dec 2014
Background
Problem
A near miss has occurred with a
prescription for posaconazole. No
form was specified on the
prescription,
but
liquid
was
intended. Because no form was
specified, tablets were dispensed
instead.
Posaconazole tablets and liquids have
very different bioavailabilities, so they
have very different doses:
The usual posaconazole dose as the
liquid is 400mg BD, or 200mg QDS.
The usual posaconazole dose as
tablets is 300mg BD for one day then
300mg OD thereafter.
The patient was therefore dispensed a significant overdose.
Some other products also have differences in the effectiveness or dosing
between formulations:
Efavirenz tablets have a dose of 600mg OD, whereas the liquid dose is 720mg OD.
Phenytoin capsules contain phenytoin sodium, whereas the liquid and Infatabs contain
phenytoin base - 100mg of phenytoin capsules is equivalent to 92mg of phenytoin
liquid or Infatabs.
Gliclazide MR tablets 30mg are equivalent to gliclazide normal release tablets 80mg.
Omeprazole is available as an unlicensed suspension and sometimes supplied in
primary care, but this is not used in The Leeds Children’s Hospital because it is not
thought to be as effective as a dispersed MUPS tablet.
Valproic acid - the equivalent amount of valproic acid available from Depakote 500mg
tablets and Epilim EC/Chrono 500mg tablets are 500mg and 433mg respectively. A
dose conversions is needed if switching between semisodium valproate and sodium
valproate (e.g. semisodium valproate 500mg to sodium valproate 600mg).
Products with different bioavailabilities for different oral formulations are relatively
rare, so it is difficult to remember all of them. However the differences are important
when encountered.
If you are working in a specialist area, make sure you are familiar with the products
that you might come across where this problem may occur.
When communicating information about these medicines (e.g. orders to dispensaries,
eDANs, letters to GPs or community pharmacists, annotations on drug cards), make
sure that you specify the form, and highlight that the form is important - don’t assume
that the person you are passing the information on to will know what you know.
LIZ MELLOR
Bleep 07659 532121
KERI MURPHY
Bleep 07659 532233
KAREN FEENEY
Bleep 80-2182
SUE PARKINSON
Bleep 80-4950
JOHN DADE
Bleep 80-6671