Antimicrobials are, together with anti-malarials, the most popular medicines that have been encountered as illegal substandard and falsified (SF) medical products. SF antimicrobials are gaining popularity both in developing and developed countries, posing a growing threat to public health. It has been demonstrated that SF products of these essential life-saving medicines could cause treatment failures, antimicrobial resistance and drug side effects [1]. In general, the evaluation of SF antimicrobials mainly focuses on the identification and quantification of the active pharmaceutical ingredients (APIs), ignoring other parameters of drug quality control [2]. In this context, SF antimicrobials containing the correct dosage of claimed APIs can exhibit poor dissolution performance. Thus, it is necessary and crucial to execute in vitro dissolution studies on SF antimicrobials to estimate the in vivo bioavailability and bioequivalence.

Real-life illegal antimicrobial samples, confiscated by inspectors from the Belgium Federal Agency for Medicines and Health Products (FAMHP), were subjected to dissolution studies. The results indicated that 9 out of 19 illegal samples failed to meet the dissolution limits prescribed by the United States Pharmacopeia. The dissolution profiles of illegal SF antimicrobials were mathematically compared to their genuine counterparts using f1 and f2-methods, which clearly demonstrate low equivalences of dissolution profiles between SF antimicrobials and genuine products. The potential low drug efficacy induced by improper dissolution of SF antimicrobials could aggravate illness and even promote antimicrobial resistance.