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Multidrug, anti-HIV amorphous solid dispersions: nature and mechanisms of impacts of drugs on each other’s solution concentrations.

Multidrug, anti-HIV amorphous solid dispersions: nature and mechanisms of impacts of drugs on each other’s solution concentrations.
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Arca HÇ, Mosquera-Giraldo LI, Dahal D, Taylor LS, Edgar KJ,


Arca HÇ, Mosquera-Giraldo LI, Dahal D, Taylor LS, Edgar KJ, (click to view)

Arca HÇ, Mosquera-Giraldo LI, Dahal D, Taylor LS, Edgar KJ,

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Molecular pharmaceutics 2017 09 05() doi 10.1021/acs.molpharmaceut.7b00203

Abstract

Drug therapy has been instrumental in prolonging the lives of patients infected by human immunodeficiency virus (HIV). In order to combat development of resistance, therapies involving three or more drugs in combination are recommended by the World Health Organization (WHO) to suppress HIV and prevent development of acquired immune deficiency syndrome (AIDS). It is desirable for multidrug combinations to be co-formulated into single dosage forms where possible, to promote patient convenience and adherence to dosage regimens, for which when amorphous solid dispersion (ASD) is particularly well-suited. We investigated multi-drug ASDs of three model anti-HIV drugs, ritonavir (Rit), etravirine (Etra), and efavirenz (Efa), in cellulosic polymer matrices. We hypothesized that the presence of multiple drugs would reduce crystallization tendency, thereby providing stable, supersaturating formulations for bioavailability enhancement. We explored new ASD polymers including cellulose acetate suberate (DSSub 0.9, CASub) and cellulose acetate adipate propionate (DSAd 0.9, CAAdP), and control commercial cellulosic polymers included 6-carboxycellulose acetate butyrate (CCAB) and carboxymethyl cellulose acetate butyrate (CMCAB). We succeeded in preparing three drug ASDs containing very high drug loadings (45% drug total; 15% of each drug); each polymer tested was effective at stabilizing the amorphous drugs in the solid phase, as demonstrated by XRD, SEM and DSC studies. In pH 6.8 dissolution studies ASDs released each anti-HIV drug over 8 h, affording supersaturated solutions of each drug, but unexpectedly failing in some cases to reach maximum possible supersaturation. In a second set of dissolution studies (pH 6.8), the cause of the observed solution concentration limitations was investigated by studying release from single- and two-drug ASDs. Concentrations of Rit, Etra and Efa achieved from three-drug ASDs were higher than those achieved from crystalline drugs. Surprisingly however, there was a decrease in the achieved drug concentrations of both Rit and Efa when they dissolved together, while Etra solution concentration was enhanced by the presence of Rit and Efa in the ASD. We demonstrate that these effects have to do primarily with solution phase interactions between the anti-HIV drugs, rather than from the drugs influencing each other’s release rate, and we suggest that such observations may indicate an important, previously inadequately recognized, and general phenomenon for ASDs containing multiple hydrophobic drugs.

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