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Lai A, Sahbaz Y, Ford L, Nguyen TH, Haque S, Williams HD, Benameur H, Scammells PJ, Porter CJH. Stabilising disproportionation of lipophilic ionic liquid salts in lipid-based formulations. Int J Pharm 2021; 597:120292. [PMID: 33581479 DOI: 10.1016/j.ijpharm.2021.120292] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2020] [Revised: 12/22/2020] [Accepted: 01/17/2021] [Indexed: 10/22/2022]
Abstract
Lipid based formulations (LBFs) can enhance oral bioavailability, however, their utility may be restricted by low drug loading in the formulation. Converting drugs to drug-ionic liquids (drug-ILs) or lipophilic salts can significantly increase lipid solubility but this approach is complicated in some cases by salt disproportionation, leading to a reduction in solubility and physical instability. Here we explore the physical stability of the weakly basic model drug, cinnarizine (CIN), when paired with a decanoate counterion (Dec) to form the drug-IL, cinnarizine decanoate (CIN.Dec). Consistent with published studies of salt disproportionation in aqueous solution, weakly acidic counterions such as Dec lead to the generation of drug-IL lipid solutions with pHs below pHmax. This leads to CIN deprotonation to the less soluble free base and precipitation. Subsequent studies however, show that these effects can be reversed by acidification of the formulation (either with excess decanoic acid or other lipid soluble acids), stimulating a pH shift to the salt plateau of CIN.Dec and the formation of stable lipid solutions of CIN.Dec. Altering formulation pH to more acidic conditions, therefore stabilises drug-ILs formed using weakly acidic lipophilic counterions, and is a viable method to promote formulation stability via inhibition of disproportionation of some drug-ILs.
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Affiliation(s)
- Anthony Lai
- Medicinal Chemistry, Monash Institute of Pharmaceutical Sciences, Monash University, 381 Royal Parade, Parkville, Victoria 3052 Australia; Drug Delivery, Disposition and Dynamics, Monash Institute of Pharmaceutical Sciences, Monash University, 381 Royal Parade, Parkville, Victoria 3052 Australia
| | - Yasemin Sahbaz
- Medicinal Chemistry, Monash Institute of Pharmaceutical Sciences, Monash University, 381 Royal Parade, Parkville, Victoria 3052 Australia; Drug Delivery, Disposition and Dynamics, Monash Institute of Pharmaceutical Sciences, Monash University, 381 Royal Parade, Parkville, Victoria 3052 Australia
| | - Leigh Ford
- Oral Drug Delivery Innovation, Chemical Division, Lonza Pharma Biotech & Nutrition, Melbourne Australia
| | - Tri-Hung Nguyen
- Drug Delivery, Disposition and Dynamics, Monash Institute of Pharmaceutical Sciences, Monash University, 381 Royal Parade, Parkville, Victoria 3052 Australia
| | - Shadabul Haque
- Drug Delivery, Disposition and Dynamics, Monash Institute of Pharmaceutical Sciences, Monash University, 381 Royal Parade, Parkville, Victoria 3052 Australia
| | - Hywel D Williams
- Oral Drug Delivery Innovation, Chemical Division, Lonza Pharma Biotech & Nutrition, Melbourne Australia
| | - Hassan Benameur
- Oral Drug Delivery Innovation, Chemical Division, Lonza Pharma Biotech & Nutrition, Strasbourg, France
| | - Peter J Scammells
- Medicinal Chemistry, Monash Institute of Pharmaceutical Sciences, Monash University, 381 Royal Parade, Parkville, Victoria 3052 Australia
| | - Christopher J H Porter
- Drug Delivery, Disposition and Dynamics, Monash Institute of Pharmaceutical Sciences, Monash University, 381 Royal Parade, Parkville, Victoria 3052 Australia; ARC Centre of Excellence in Convergent Bio-Nano Science and Technology, Monash University, 381 Royal Parade, Parkville, Victoria 3052 Australia.
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