Antimicrobial storage conditions: authors’ response

E. S. Mitema1,* and G. M. Kikuvi2

1 Faculty of Veterinary Medicine, Department of Public Health, Pharmacology and Toxicology, University of Nairobi, PO Box 29053, Nairobi; 2 Department of Veterinary Services, Central Veterinary Investigation Laboratories, Kabete, Private Bag, 00625 Kangemi, Nairobi, Kenya


* Corresponding author. Tel: +254-20-630034; Fax: +254-20-631325/631007; Email: esmitema{at}uonbi.ac.ke

Keywords: tropical conditions , national antimicrobial consumption , potency

Sir,

We have noted with interest the point made by Arya & Agarwal1 on our recent publication2 and make the following comments. The storage temperature conditions for antimicrobials at the warehouses of the manufacturers were between 22 and 27°C. We agree that inappropriate storage conditions may alter the biopharmaceutical properties of some drugs but caution that there are contrasting reports on the effects of tropical conditions on antimicrobial drugs. For example, in a study to investigate the influence of tropical climate conditions on drug content, in vitro dissolution and oral bioavailability of different formulations of two essential drugs marketed in Tanzania, the drug content and drug release from all the tested ciprofloxacin formulations were within USP-24 requirements and remained stable during storage at simulated tropical conditions. Oral bioavailability was also not influenced by tropical conditions.3 The stability of essential drugs (ampicillin, benzylpenicillin, phenoxymethylpenicillin and tetracycline) was not affected during shipment to the tropics after being exposed to much higher temperatures and humidity than recommended by the manufacturer, with temperatures recorded within packs ranging from –3.5 to 42.4°C and humidity ranging from 20% to 88%.4 A controlled longitudinal study on the quality and stability of essential drugs in rural Zimbabwe showed that even under the most adverse tropical conditions, clinically relevant instability of these agents is rare.5

Evidence of potency is an important aspect to consider whilst procuring data about consumption of antimicrobials in developing countries. However, in order to achieve this, one would have to establish potency for each drug on the market, a difficult, unrealistic and expensive exercise, considering the limited funding for research in developing countries. Otherwise, assumptions would be based on random sampling of imported or locally manufactured drugs. Accurate information relating to national antibiotic consumption would be essential in order to extrapolate the impact of these storage issues.

References

1 . Arya, S. C. & Agarwal, N. (2005). Comment on: Surveillance of the overall use of antimicrobial drugs in humans over a 5 year period (1997–2001) in Kenya. Journal of Antimicrobial Chemotherapy 55, doi:10.1093/jac/dki061.

2 . Mitema, E. S. & Kikuvi, G. M. (2004). Surveillance of the overall use of antimicrobial drugs in humans over a 5 year period (1997–2001) in Kenya. Journal of Antimicrobial Chemotherapy 54, 966–7.[Free Full Text]

3 . Risha, P. G., Vervaet, C., Vergote, G. et al. (2003). Drug formulations intended for the global market should be tested for stability under tropical climatic conditions. European Journal of Clinical Pharmacology 59, 135–41.[ISI][Medline]

4 . Hogerzeil, H. V., Battersby, A., Srdanovic, V. et al. (1992). Stability of essential drugs during shipment to the tropics. British Medical Journal 304, 210–2.[ISI][Medline]

5 . Nazerali, H. & Hogerzeil, H. V. (1998). The quality and stability of essential drugs in rural Zimbabwe: controlled longitudinal study. British Medical Journal 317, 512–3.[Free Full Text]





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