Amoxicillin capsules

This is a hospital drug supplied by one manufacturer only. The number of GMS samples tested was small (6). Initial potency was within specifications (92.5-110%, BP), although it tended toward the lower limit (95% confidence intervals for mean 93.8-98.5%). Turnover at hospitals was slow (mean facility storage time 6.4 months, maximum 15 months). 92% of facility samples had expended more than half the shelf-life (two or three years) and showed no sign of instability. Four expired samples were also within specifications at mean age 28.0 months.

No mean loss was found in the longitudinal series data after a mean interval of 7.7 months, however only a small sample of six pairs was obtained, Amoxicillin capsules were stable, justifying the recent extension of shelf-life.

Acetylsalicylic acid tablets

GMS had large stocks from one manufacturer (C) at the beginning of this study. The mean age was over one year at the time of sampling, initial potency was well within specifications limits (92.5-110%, BP) and all facility samples passed. The facility sample group was large (79) and showed no difference between the two manufacturers. Potency was maintained even in the later part of shelf-life.

No loss of potency was seen in the longitudinal series (in which only manufacturer C was represented) after a mean interval of 6.9 months. The conclusion is that acetylsalicylic acid tablets are stable in the Zimbabwe setting,

Phenoxymethylpenicillin tablets

A single manufacturer supplied this drug which has a shelf-life of four years. Initial potency was well within specification limits (92.5-107.5%, BP), Eight (14%) facility samples failed, but all of these failures were above the upper limit. The maximum value among these failures was 113.9%. These "high failures" do not have any negative therapeutic consequences. There was no sign of instability, however facility samples were young (mean age 12.5 months) in relation to shelf-life. The turnover of this drug at facilities was usually fast (mean facility storage time 5.4 months). However, a few "worst case" samples were obtained aged up to 33.3 months (see Figure 1 in Annex 1.6), but they showed no loss of potency. Phenoxymethylpenicillin tablets can therefore be considered stable in this setting.

Tetracycline capsules

Supplies were obtained from three manufacturers during the period of study. No difference was found between them, and no initial qualify problem was seen. All facility assay results were within specifications (90-125%, USP).

No consistent loss of potency was found in GMS/facility sample pairs after a mean interval of 5.7 months. There was no sign of instability, but facility samples were relatively young (mean age 10.1 months) and only 5 (8%) samples had expended half of the three year shelf-life.

A policy decision to remove tetracycline capsules from the essential drugs list in Zimbabwe in favour of doxycycline capsules reduces the relevance of further study of tetracycline in Zimbabwe.

Benzylpenicillin injection

This drug is stocked at PHC facilities in order that a single dose can be given before referral; it is infrequently used. The supply quantity is often excessive due to the large standard pack size (100 vials). Consequently the facility storage time is long: mean 13.4 months with a maximum of 39.4 months. At the moment of collection, 68% of samples had expended more than half of their four year shelf-life. No low potency was seen in 41 facility samples representing the "worst case scenario" (PHC facility in hot lowland area with slow transport). Pharmacopoeal specification limits are narrow (95-105%, BP). One sample was above the upper limit (106.1%) but this had no medical relevance. Since benzylpenicillin injection appeared very stable from the early facility samples it was not included in the longitudinal study.