In view of the apparent problems associated with the stability of oxytocic drugs and the lack of practical and consistent guidelines on their storage under tropical conditions, this study was designed to address the following questions:
(1) What is the pattern of stability of the common injectable oxytocics (ergometrine maleate, methylergometrine maleate and oxytocin) regularly supplied to tropical countries by the main international non-profit suppliers? Are there significant differences between the drugs and between brands of the same drug?
(2) What Is the effect of long-term dark storage at 25 and 30°C on the amount of active ingredient?
(3) What is the effect of short-term exposure to 30 and 40°C and of short-term exposure to light?
(4) Can guidelines for the selection and storage of oxytocic drugs in tropical climates be developed?
In addition, the following questions with regard to (methyl)ergometrine were formulated in the course of the study:
(5) Is there a correlation between the colour of the solution and its level of active ingredient?
(6) Can an observed loss of active ingredient be (partially) explained by a different pH or oxygen content of the product?
The study consists of two components. The first is a series of small field surveys on the level of active ingredient in samples of oxytocic drugs taken from health facilities in Gambia, Malawi, Sudan and Zimbabwe. The second and largest component is a study on the stability of injectable oxytocic drugs under simulated tropical conditions, measuring the level of active ingredient at various temperature and light conditions over time. This part of the study covers all brands of (methyl)ergometrine and oxytocin injection that are most commonly supplied by the two largest non-profit drug suppliers IDA (Amsterdam) and UNICEF (Copenhagen).
The main outcome measure is the amount of active ingredient in the sample, expressed as percentage of the stated amount. Additional outcome measures are the colour of the solution, pH and oxygen content.