Modified Release of Acetaminophen from Matrix Tablet Formulations: Influence of Tablet Geometry

Background: Acetaminophen (APAP) or paracetamol is a widely used over-the-counter, analgesic (common conditions treated include headaches, backache, toothache, muscle aches, arthritis, sore throat etc.) and antipyretic drug. It can be administered orally, in the form of a tablet (plain, effervescent, orodispersable, etc.) or liquid, rectally in the form of a suppository or by injection (intravenously or intramuscularly). It is well absorbed orally with a plasma elimination half-life ranging from 1 to 4 h. The modified release oral formulation can prolong its therapeutic effects by maintaining APAP average plasma concentrations. Objective: In the context of this work, two APAP formulation tablets with different geometries were produced from standard pharmaceutical excipients to investigate the role of altered tablet geometry in modified oral drug delivery. Methods: APAP tablets were prepared by direct compression, using hydroxypropyl methylcellulose (HPMC K15M), polyvinylpyrrolidone (PVP, MW: 55,000) and magnesium stearate, as ingredients. The release profiles were probed in aqueous dissolution media (pH 1.2 and 6.8) to simulate the conditions in the gastrointestinal tract in a United States Pharmacopeia (USP) dissolution paddle apparatus II and analyzed using an ultraviolet (UV) spectrophotometer (λmax = 244 nm). Results: The results indicated that the tablets were within the acceptable range of all evaluation parameters (tablet dimensions, drug content, weight variation, and breaking force) as defined by the international standards stated in the US Pharmacopoeia. The dissolution results showed that the APAP’s release profile was controlled by the tablets’ different geometries and, specifically the surface area (SA) and the surface area/volume (SA/V) ratio of the different tablets. The tablets with smaller SA/V ratios and SA showed slower drug release, indicative of a modified release motif. Conclusion: Altered tablet geometry plays an important role in APAP-modified oral drug delivery.