Background: Widespread access to good quality antihypertensive medicines is a critical component for reducing premature cardiovascular disease (CVD) mortality. Poor-quality medicines pose serious health concerns; however, there remains a knowledge gap about the quality of cardiovascular medicines available in low- and middle-income countries.

Objectives: The aim of this study was to determine the quality of generic antihypertensive medicines available in the retail market of a developing country.

Methods: Samples of the 2 most commonly prescribed classes of antihypertensive medicines were collected from 3 states in 3 different geopolitical zones in Nigeria following a semirandom sampling framework. Medicine samples were purchased by mystery shoppers from 22 pharmacy outlets from 6 local government areas across the 3 states. Medicine quality was determined by measuring the amount of stated active pharmaceutical ingredient using high-performance liquid chromatography with photodiode array detection and classified according to their compliance to the specified pharmacopeia tolerance limits for each antihypertensive drug.

Results: Amlodipine and lisinopril were identified as the most commonly prescribed antihypertensive drugs in Nigeria. In total, 361 samples from 22 pharmacies were collected and tested. In total, 24.6% of amlodipine and 31.9% of lisinopril samples were of substandard quality and significantly more samples purchased in rural (59 of 161, 36.7%) compared with urban (32 of 200, 16%) outlets were found to be of substandard quality (p < 0.001). No falsified samples of either amlodipine or lisinopril were detected. There was large variation in price paid for the antihypertensive medicines (range ₦150 to ₦9,750). Of the 24 pharmacy outlets surveyed, 46% stated that patients did not always require a prescription and 21% had previously reported a medicine as falsified or substandard.

Conclusions: More than one-quarter of some commonly prescribed antihypertensive medicines available in Nigeria may be of substandard quality. Enhanced quality assurance processes in low- and middle-income countries, such as Nigeria, are needed to support optimum management.

Highlights

• Management of hypertension can largely be achieved through availability of and adherence to qualitative evidence-based medicines. There is very little research examining the quality of antihypertensive medicines available in the retail market of low- and middle-income countries.
• In total, 361 samples of amlodipine and lisinopril were collected from 22 pharmacies and their stated active pharmaceutical ingredient was measured.
• More than a quarter of some commonly prescribed antihypertensive medicines available in Nigeria appear to be of substandard quality (samples had more or less stated active pharmaceutical ingredient than stated in the United States Pharmacopeia–specified tolerance limits range).
• However, the proportion of substandard quality was not statistically different for amlodipine and lisinopril, and significantly more samples purchased in rural compared with urban outlets were of substandard quality.
• No falsified samples (containing no stated active pharmaceutical ingredient) of either amlodipine or lisinopril were detected.
• Enhanced quality assurance processes in low- and middle-income countries such as Nigeria are needed to support optimum management.