Measurements of bioavailability

Measurement of bioavailability, PCt profile, absolute bioavailability and relative bioavailability

1. Measurements of Bioavailability Presented by Naga Chandrika Pallam , Department of Pharmaceutics Geethanjali College of Pharmacy, Cheeryal , Hyd. 1

2. Bioavailability Bioequivalence Bioavailability means the rate and extent of drug, which reaches the systemic circulation unchanged following the administration of dosage form . Bioequivalence is a relative term, which denotes that the drug substance in two or more identical dosage forms reaches the systemic circulation at the same relative rate and to same relative extent. DEFINITIONS 2

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4. Measurements of Bioavailability 4

5. Plasma Level Time Studies 5

6. PLASMA LEVEL TIME STUDIES 1. Cmax : It is peak plasma concentration. It increases with dose as well as increase in rate of absorption 2. Tmax : The peak time at which Cmax attended. 3. AUC : Area under Curve explains about amount of drug. 6

7. Urinary excretion data studies 7

8. PHARMACODYNAMIC METHODS 1. ACUTE PHARMACOLOGICAL RESPONSE: When bioavailability measurement by pharmacokinetic methods is difficult, inaccurate or non-reproducible this method is used. Such as ECG, EEG, pupil diameter. It can be determined by dose response graphs. DISADVANTAGES: Pharmacological response is variable and accurate correlation drug and formulation is difficult. Observed response may be due to active metabolites . 8

9. 2. THERAPEUTIC RESPONSES This method is based on observing clinical response in patients. Demerits: Quantitative of observed response is too improper. Physiological variations maybe present between patients. If multiple dose protocols are not involved. Patient receive only single dose for few days or a weak. The patients receiving more than one drug treatment may be compromised due to drug-drug interactions. 9

10. REFERENCES Biopharmaceutics and pharmacokinetics A treatise by D.M. Brahmankar , Sunil B. Jaiswal , second edition, Vallabh Prakash , pg. no. 315-363. Basics of pharmacokinetics, Leon Shargel , fifth edition, willey publications, pp- 453-490. www.google.com 10

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