E-drug: Re: Drug Stability-oxytocics and misoprostol (1)
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I think the most complete study on the stability of ergometrine and other
oxytocics is the review by Godfrey Walker and myself: Hogerzeil HV, Walker
GJA. Instability of (methyl)ergometrine in tropical climates: an overview.
Eur J Obs Gyn Repr Biol, 69 (1996) 25-29. It summarizes nine WHO studies in
this respect.
The findings can be summarized as follows: injections and tablets of
ergometrine and methylergometrine are very unstable in tropical climates,
but there are large differences between brands. Exposed to light, most
ergometrine ampoules lose about 20-30% of their potency per month. The
practice of keeping a few ampoules ready on a tray in the labour ward
results in a totally ineffective product and should be discouraged. Any
ampoule with a colour of the content different from water (compare the
solution with an ampoule of water against a
well-lit white background) implies that more than 10% the ingredients have
degraded, and that the ampoule should not be used.
Methylergometrine is not more stable than ergometrine; injectable oxytocin
is usually more stable than (methyl)ergometrine. Oral and buccal dosage
forms are less stable than parenteral ones.
Practical recommendations are (1) careful supplier selection and (2)
refrigerated dark storage (3) international transport by air, not sea. In
general, it is safe to try to use the injections within one year of
manufacture, irrespective of the official expiry date.
In view of better stability in tropical climates, similar costs, fewer side
effects and comparative efficacy, parenteral oxytocin, rather than
parenteral ergometrine, is the drug of choice in the prevention and
treatment of post-partum haemorrhage.
Dr Hans Hogerzeil
WHO Action Programme on Essential Drugs
hogerzeilh@who.ch
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