In vitro evaluation of a sustained-release veterinary peroral pellet preparation.
In a preceding in vivo study in horses, wide interindividual variation was found in the extent of bioavailability and time to reach peak concentration after peroral administration of one specific theophylline sustained-release dosage form. The purpose of the present study was to investigate the factors of potency, the pH of dissolution medium, the enzymes in the dissolution medium, and the crushing of the pellets on in vitro performance. The results show a wide variation in potency for the individual units, an increase in release rate with increasing pH, and an increase in release rate if the pellets are crushed. The wide variation in potency explains the variation found in absolute bioavailability, and the increase in release rate when the pellets are crushed explains the differences seen in peak plasma times, since the pellets will be chewed to varying degrees by the horse.
Ritschel
W A
WA
University of Cincinnati Medical Center, Division of Pharmaceutics and Drug Delivery Systems, OH 45267.
Agrawala
P
P
Kraeling
M
M
Sathyan
G
G
Berger
K
K
D000818:Animals; D002626:Chemistry, Pharmaceutical; D003692:Delayed-Action Preparations; D006207:Half-Life; D006736:Horses; D006863:Hydrogen-Ion Concentration; D012995:Solubility; D013806:Theophylline / Q000008:administration & dosage
D003692:Delayed-Action Preparations; D013806:Theophylline