In vitro dissolution of expired antibiotics

The most common pharmaceutical formulations for antibiotics are the tablets and hard gelatin capsules. The typical shelflife of these dosage forms is five years. In the most countries of the world it is required by the law that the expired medications have to be disposed following the respective regulations. Furthermore, it is common sense not to use the expired medications. The present study was intended as an academic investigation only and it was aimed to examine the in vitro dissolution performance of at least 10 years expired amoxicillin, ampicillin, or doxycycline tablets or hard gelatin capsules. The dissolution tests were performed using the Apparatus 2 technique as described in the US Pharmacopoeia (USP 35/ NF30) respective monographs. For the comparison, the non-expired antibiotics registered in European Union (EU) and available in the community pharmacies of Estonia were used. The respective USP tolerance limits for the dissolution tests were applied to qualify the formulations tested as “passed” or “failed”. Expectedly, all EU registered nonexpired formulations passed the USP test. But all tablets and hard gelatin capsules of the expired antibiotics passed the USP tests as well. In conclusion, our results demonstrate that the shelf-life of antibiotics in the dosage forms of tablets or hard gelatin capsules is underestimated what concerns their in vitro dissolution performance. However, the authors in no way promote the use of expired medications, neither was it completely out of the study to give any hint on the therapeutic value of these expired medications.