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Dosage Forms and Delivery Systems: Overview |  |
| A diverse range of dosage forms and delivery systems has been developed to provide for the care and welfare of animals. The development of dosage forms draws on the discipline of biopharmaceutics, which integrates an understanding of formulations, dissolution, stability and controlled release (pharmaceutics); absorption, distribution, metabolism, and excretion (pharmacokinetics, PK); concentration-effect relationships and drug-receptor interactions (pharmacodynamics, PD), and
treatment of the disease state (therapeutics). Formulation of a dosage form typically involves combining an active ingredient and one or more excipients; the resultant dosage form determines the route of administration and the clinical efficacy and safety of the drug. Optimization of drug doses is also critical to achieving clinical efficacy and safety. Increasingly, a PK/PD model that describes the drug response is the basis of dose optimization. The PK and PD phases are linked by
the premise that free drug in the systemic circulation is in equilibrium with the receptors. The PD phase involves interaction of the drug with receptor, which triggers post-receptor events, and eventually leads to a drug effect (see
Drug Concentration and Effect). |
| Drug delivery strategies for veterinary formulations are complicated by the diversity of species and breeds treated, the wide range in body sizes, different husbandry practices, seasonal variations, cost constraints associated with the value of the animal being treated, the persistence of residues in food and fiber (wool, mohair), and the level of convenience, among other factors. Innovative solutions have been developed to meet many of these challenges (eg, the convenient dosing
option offered by topical spot-on formulations for treating external and internal parasites on dogs and cats, the microencapsulation of NSAID as a means of masking taste when these agents are added to the rations of horses). Unique opportunities also exist for controlled-release drug delivery systems in veterinary medicine, and many such systems are on the market. For example, a range of controlled-release boluses have been developed for delivering antimicrobials, anthelmintics,
production enhancers, nutritional supplements, and other drugs to ruminants. |
