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(-)-Phenserine ("phenserine") and (+)-phenserine (posiphen; buntanetap) are longer-acting enantiomeric analogs of physostigmine with demonstrated promise in the treatment of Alzheimer's and Parkinson's diseases. Both enantiomers have short plasma half-lives, and their pharmacokinetics might be improved through the use of either once or twice-daily administration of an extended-release dosage form. Phenserine was observed to form a colored degradation product in near-neutral and alkaline pH environments, and at pH 7, the half-life of posiphen was determined to be ~ 9 h (40 °C). To limit luminal degradation which would reduce bioavailability, a gastroretentive tablet composed of a polyethylene oxide-xanthan gum matrix was developed. When placed in simulated gastric fluid (pH 1.2), approximately 70% of the phenserine was released over a 12 h period, and no degradants were detected in the release medium. In comparison, a traditional hydrophilic-matrix, extended-release tablet showed measurable amounts of phenserine degradation in a pH 7.2 medium over an 8 h release interval. These results confirm that a gastroretentive tablet can reduce the luminal degradation of phenserine or posiphen by limiting exposure to neutral pH conditions while providing sustained release of the drug over at least 12 h. Additional advantages of the gastroretentive tablet include reduced gastric and intestinal concentrations of the drug resulting from the slower release from the gastroretentive tablet which may also limit the occurrence of the dose-limiting GI side effects previously observed with immediate-release phenserine capsules., (© 2024. The Author(s), under exclusive licence to American Association of Pharmaceutical Scientists.)

Polyethylene oxide (PEO) is a widely used polymer in the development of abuse-deterrent oral formulations. Different manufacturing processes including direct compression (DC) followed by sintering, wet granulation (WG) followed by compression and sintering, and hot melt extrusion (HME) can be used to manufacture abuse-deterrent oral drug products. Three different manufacturing processes (DC, WG, HME) were evaluated to test the retention of their abuse-deterrent features following attempts to grind the tablets or extrudates. In vitro drug release studies were conducted on 10% and 32% drug-loaded tablets/extrudates prepared using these manufacturing methods, and the release profiles from all formulations showed good extended-release properties. Drug content analysis on the granules obtained from tablets prepared by direct compression showed non-uniform drug distribution where an unexpectedly high drug content was present in the smallest size (< 250 µm) granules, sizes which are likely to be inhaled by abusers. Granules from tablets prepared by wet granulation showed improved drug distribution across all granule sizes formed after grinding. Drug content testing on the granules obtained from extrudates prepared using hot melt extrusion showed excellent drug content uniformity along with sufficient strength to resist grinding into smaller particles. The retention of the abuse-deterrent properties of a dosage form following attempts to extract or abuse the drug is an important product characteristic, and the product design, formulation components, and manufacturing processes can all play critical roles in the retention of the desired abuse-deterrent properties., (© 2021. The Author(s), under exclusive licence to American Association of Pharmaceutical Scientists.)

Abuse-deterrent formulations (ADFs) using physical/chemical barrier approaches limit abuse by providing resistance to dosage form manipulation to limit drug extraction or altered release. Standardizing in vitro testing methods to assess the resistance to manipulation presents a number of challenges, including the variation in particle sizes resulting from the use of various tools to alter the tablet matrix (e.g., grinding, chipping, crushing). A prototype, direct-compression ADF using a sintered polyethylene oxide (PEO) matrix containing dextromethorphan, an enantiomeric form of the opioid, levorphanol, was developed to evaluate testing methodologies for retention of abuse-deterrent properties following dosage form tampering. Sintered PEO tablets were manipulated by grinding, and drug content and release were evaluated for the recovered granules. Drug content analysis revealed that higher amounts of drug were contained in the smaller size granules (< 250 μm, 190% of the theoretical amount) compared with the larger particles (> 250 μm, 55-75% of theoretical amount). Release testing was performed on various size granule fractions (> 850 μm, 500-850 μm, 250-500 μm, and < 250 μm) using USP type I (basket), type II (paddle), and type IV (flow-through) apparatus. The USP type I and type II apparatus gave highly variable release results with poor discrimination among the release rates from different size granules. The observed sticking of the hydrated granules to the baskets and paddles, agglomeration of hydrated granules within the baskets/vessels, and ongoing PEO hydration with subsequent gel formation further altered the particle size and impacted the rate of drug release. The use of a flow-through apparatus (USP type IV) resulted in improved discrimination of drug release from different size granules with less variability due to better dispersion of granules (minimal sticking and aggregation). Drug release profiles from the USP type IV apparatus showed that the larger size granules (> 500 μm) offered continued resistance to drug release following tablet manipulation, but the smaller size granules (< 500 μm) provided rapid drug release that was unhindered by the hydrated granule matrix. Since < 500-μm size particles are preferred for nasal abuse, improved direct-compression ADF formulations should minimize the formation of these smaller-sized particles following tampering to maintain the product's abuse-deterrent features.