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Rapid delivery of diazepam from supersaturated solutions prepared using prodrug/enzyme mixtures: toward intranasal treatment of seizure emergencies.

ABSTRACT: Current treatments for seizure emergencies, such as status epilepticus, include intravenous or rectal administration of benzodiazepines. While intranasal delivery of these drugs is desirable, the small volume of the nasal cavity and low drug solubility pose significant difficulties. Here, we prepared supersaturated diazepam solutions under physiological conditions and without precipitation, using a prodrug/enzyme system. Avizafone, a peptide prodrug of diazepam, was delivered with--Aspergillus oryzae (A.O.) protease, an enzyme identified from a pool of hydrolytic enzymes in assay buffer, pH 7.4 at 32°C. This enzyme converted avizafone to diazepam at supersaturated concentrations. In vitro permeability studies were performed at various prodrug/enzyme ratios using Madin-Darby canine kidney II-wild type (MDCKII-wt) monolayers, a representative model of the nasal epithelium. Monolayer integrity was examined using TEER measurement and the lucifer yellow permeability assay. Prodrug/drug concentrations were measured using HPLC. Enzyme kinetics with avizafone-protease mixtures revealed K(M)?=?1,501?±?232 ?M and V(max)?=?1,369?±?94 ?M/s. Prodrug-protease mixtures, when co-delivered apically onto MDCKII-wt monolayers, showed 2-17.6-fold greater diazepam flux (S?=?1.3-15.3) compared to near-saturated diazepam (S?=?0.7). Data for prodrug conversion upstream (apical side) and drug permeability downstream (basolateral side) fitted reasonably well to a previously developed in vitro two compartment pharmacokinetic model. Avizafone-protease mixtures resulted in supersaturated diazepam in less than 5 min, with the rate and extent of supersaturation determined by the prodrug/enzyme ratio. Together, these results suggest that an intranasal avizafone-protease system may provide a rapid and alternative means of diazepam delivery.

SUBMITTER: Kapoor M

PROVIDER: S-EPMC4012037 | biostudies-literature | 2014 May

REPOSITORIES: biostudies-literature

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Rapid delivery of diazepam from supersaturated solutions prepared using prodrug/enzyme mixtures: toward intranasal treatment of seizure emergencies.

Kapoor Mamta M Winter Tate T Lis Lev L Georg Gunda I GI Siegel Ronald A RA

The AAPS journal 20140404 3

Current treatments for seizure emergencies, such as status epilepticus, include intravenous or rectal administration of benzodiazepines. While intranasal delivery of these drugs is desirable, the small volume of the nasal cavity and low drug solubility pose significant difficulties. Here, we prepared supersaturated diazepam solutions under physiological conditions and without precipitation, using a prodrug/enzyme system. Avizafone, a peptide prodrug of diazepam, was delivered with--Aspergillus o ...[more]

PMID: 24700272

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Project description:Amorphous solid dispersions of pharmaceuticals often show improved solubility over crystalline forms. However, the crystallization of amorphous solid dispersions during storage, or from elevated supersaturation once dissolved, compromise the solubility advantage of delivery in the amorphous phase. To combat this phenomenon, polymer additives are often included in solid dispersions to inhibit crystallization; however, the optimal properties for polymer to stabilize against crystallization are not fully understood, and furthermore, it is not known how inhibition of precipitation from solution is related to the propensity of a polymer to inhibit crystallization from the amorphous phase. Here, polymers of varied hydrophobicity are employed as crystallization inhibitors in supersaturated solutions and amorphous solid dispersions of the BCS Class II pharmaceutical ethenzamide to investigate the chemical features of polymer that lead to long-term stability for a hydrophobic pharmaceutical. A postpolymerization functionalization strategy was employed to alter the hydrophobicity of poly( N-hydroxyethyl acrylamide) without changing physical properties such as number-average chain length. It was found that supersaturation maintenance for ethenzamide is improved by increasing the hydrophobicity of dissolved polymer in aqueous solution. Furthermore, amorphous solid dispersions of ethenzamide containing a more hydrophobic polymer showed superior stability compared to those containing a less hydrophobic polymer. This trend of increasing polymer hydrophobicity leading to improved amorphous stability is interpreted by parsing the effects of water absorption in amorphous solid dispersions using intermolecular interaction strengths derived from global structural analysis. By comparing the structure-function relationships, which dictate stability in solution and amorphous solid dispersions, the effect of hydrophobicity can be broadly understood for the design of polymers to impart stability throughout the application of amorphous solid dispersions.

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Rapid delivery of diazepam from supersaturated solutions prepared using prodrug/enzyme mixtures: toward intranasal treatment of seizure emergencies.

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Rapid delivery of diazepam from supersaturated solutions prepared using prodrug/enzyme mixtures: toward intranasal treatment of seizure emergencies.

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