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Absorption rate limit considerations for oral phosphate prodrugs
Tycho Heimbach1, Doo-Man Oh, Lilian Y Li
1The University of Michigan, College of Pharmacy, 428 Church Street, Ann Arbor, Michigan 48109, USA.
Pharmaceutical Research
|June 24, 2003
Summary
Phosphate ester prodrugs can enhance drug absorption for poorly soluble compounds. However, their effectiveness depends on drug properties like permeability and solubility, with albumin influencing highly lipophilic drugs.
Area of Science:
- Pharmaceutical Sciences
- Drug Delivery
- Biopharmaceutics
Background:
- Poorly soluble drugs present significant challenges in oral drug delivery.
- Phosphate ester prodrugs offer a strategy to improve drug absorption.
- Understanding the biopharmaceutical properties of prodrugs is crucial for successful development.
Purpose of the Study:
- To evaluate the efficacy of phosphate ester prodrugs in enhancing the absorptive flux of poorly soluble parent drugs.
- To identify characteristics of ideal phosphate prodrug candidates.
Main Methods:
- In vitro absorptive transport studies using Caco-2 cell monolayers.
- In vivo absorption studies in rats.
- Evaluation of prodrugs with varying aqueous solubilities, including Hydrocortisone-phosphate, Fosphenytoin, TAT-59, and Entacapone phosphate.
Main Results:
- Significant increases in absorptive flux were observed for DP-TAT-59 (9.8-fold) and phenytoin (3.3-fold).
- Hydrocortisone-phosphate did not improve hydrocortisone flux.
- Serosal albumin significantly enhanced the permeability of the highly lipophilic DP-TAT-59.
Conclusions:
- Phosphate prodrugs are most effective for high permeability, low solubility (BCS Class II) drugs.
- Prodrugs may not offer advantages for low-dose BCS Class II drugs or drugs with limited permeability.
- Albumin should be included in transport studies for highly lipophilic parent drugs.