Quality of timolol eye drops marketed in Kinshasa, Democratic Republic of the Congo

Abstract

To assess the quality of timolol eye drops sold in Kinshasa, Democratic Republic of Congo (DRC). Seven samples of timolol maleate 0.5% were purchased over the counter in seven randomly selected public pharmacies in 3 neighborhoods in Kinshasa. They were submitted to a quality assessment that included visual inspection, spectrophotometry, high performance liquid chromatography (HPLC), and bacteriologic assessment. The samples came from France (n=2), India (n=2) and DRC (n=3). Overall, 3 (2 from India and 1 from the DRC) of the 7 samples, or 3 out of the 5 from developing countries, showed various abnormalities consistent with substandard drugs. One sample (India) demonstrated an incorrect pH, while 3 (2 from India and one from the DRC) had lower than stated volumes as well as lower than required concentrations of the active pharmaceutical ingredient. In addition, one sample from the DRC was bacteriologically contaminated. These results suggest that some timolol maleate eye drops from Congolese and Indian manufacturers sold in Kinshasa are of substandard quality. This may reflect deficiencies in the manufacturers and local authorities charged with regulation of the quality control and sale of pharmaceuticals. Passing a visual inspection does not necessarily indicate that a drug is not substandard. Analytical chemistry testing and bacteriologic analysis are required to determine with certainty the quality of the drug.