The conclusion of the study is therefore that ergometrine injection and procaine penicillin injection show signs of instability. This conclusion is based on a higher failure rate at facilities, a difference of mean assay values between GMS and facility samples and a significant loss of active ingredient in the longitudinal sample pairs.

In the case of ergometrine injection, the findings confirm earlier concerns. It is very unfortunate that marked instability of this essential and potentially life-saving drug is now confirmed in so many developing countries, concerning products of many different manufacturers, In-vitro studies suggest that oxytocin is usually more stable, but its use as an alternative in the prevention of post-partum haemorrhage is still disputed. With regards to ergometrine, some products are of acceptable stability when stored (not necessarily transported) under refrigeration. Careful supplier selection and quality control (at least a visual check) of all incoming batches is mandatory.

The instability of procaine penicillin injection is not in line with the results of studies from other countries. It is probably due to the special formulation of the drug (a suspension). The moderate loss of active ingredient occurred in a period of only 4.3 months, and the loss may be much higher in the course of the full shelf-life.

Another conclusion of the study is that poor quality at the endpoint is often due to poor initial quality rather than instability (in Zimbabwe this applies to retinol capsules, ampicillin injection and possibly epinephrine injection).

With very few exceptions, one can therefore conclude that the quality at the end-user level will be acceptable as long as the initial quality is assured. This is both good news and bad news. Good because the instability of essential drugs does not seem to be a general problem, and also because nearly all drugs of initially good quality do not seem to deteriorate under tropical conditions. The results of stability studies in temperate climates or under simulated conditions are therefore also applicable in tropical climates and developing countries. This conclusion is bad news because poor quality may occur with any drug. This implies that quality assurance, supplier selection and quality control are needed for all drugs. Apart from ergometrine injection, there are very few "high-risk" drugs.

It should also be noted that the study produced an overall high confidence in the quality of locally produced drugs at the user level with a few well-defined exceptions. The fact that the selected antibiotics showed no serious problems is a particularly positive finding in view of the therapeutic importance and expenditure value that this class of drugs represents. These findings were consistent with previous studies.