Lecture-17 - Sources of variation in drug responses Dosing...

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Sources of variation in drug responses Dosing amounts and schedules are determined empirically, based on extensive clinical observations. These doses are those that have therapeutic efficacy in most patients on most occasions, and produce the desired therapeutic effect with an acceptably low risk of toxicity. If a normal dose of a drug is prescribed why do some patients show either too much or too little response? 1. Compliance? Did patient take drug? 2. Bioavailability? If drug was taken properly, was it absorbed properly and delivered to the systemic circulation? 3. Pharmacokinetics? Was the drug distributed normally in the body? 4. Pharmacodynamics? Did target tissue respond to drug in the expected manner?
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Compliance Most patients fully intend to follow their physician’s instructions regarding their prescriptions. Indeed, 97% of prescriptions are filled within 5 days. So, why is patient compliance an issue? Compliance with physician’s instructions is variable and depends on a number of factors. 1. Duration of treatment: There is lowered compliance for drugs that must be taken for a long time. 2. Complexity of the dosing regimen (inconvenience): Ameliorated somewhat by marketing of pharmaceutical mixtures (eg. glucocorticoid and β -adrenoceptor agonist administered in one dose for asthma), but this results in loss of therapeutic flexibility. 3. Patient’s perception of the seriousness of the disease and of the importance and efficacy of treatment.
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This note was uploaded on 10/27/2009 for the course BIO 51310 taught by Professor Sisson during the Spring '08 term at University of Texas at Austin.

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Lecture-17 - Sources of variation in drug responses Dosing...

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