Methods of improving bioavailability
- 2. Concept of Bioavailability A schematic illustration of the steps involved in the release and absorption of a drug taken as an oral solid dosage form is presented in figure Processes influencing the bioavailability of orally administered drugs.
- 3. Methods of Improving Bioavailability There are three major approaches in overcoming the bioavailability problems. 1. The pharmaceutical approach: 2. The pharmacokinetic approach: 3. The biological approach:
- 4. Methods of Improving Bioavailability Methods Mechanism involved Methodology Examples Use of co- solvent Increase in solubility of drug Addition of co- solvent ethanol, propylene, glycol, glycerin Analgesic syrups of paracetamol Use of solid solution Improving solubility by preparing sol-gel form of the drug Fusion, melting Succinic acid Alternation of pH of solvent Changing the pH of drug in solution Salt formation, addition of buffer Buffered tablets of aspirin Micronization Increasing the effective surface area of drug by decreasing particle size By spray drying and by use of fluid energy mill Griesiofulvin and several steroidal and sulpha drugs
- 5. Bioavailability Study Characteristics The evaluation of a drug product bioavailability study involves them consideration of various factors. Some are: 1. Drug (a) The drug substance in each product must be the same (b) Bioavailability studies are conducted to compare two or more products (c) Different chemical substances cannot be compared (d) Compare the drug products with the same drug in each dosage form
- 6. Bioavailability Study Characteristics 2. Drug product : (a) Comparison is made between two or more similar products containing exactly the same chemical substance. (b) Different dosage form can be compared when they contain same drug.
- 7. Bioavailability Study Characteristics 3. Subjects : Health Age Weight Enzyme status Design Number Assay
- 8. Bioavailability Studies • Bioavailability studies are designed to determine either an absolute BA or relative BA. • They can be used to compare different route of administration. • Ex: oral versus IV, IP versus IM. • Advantages - ➢The patient will be benefitted from the study ➢Reflects better the therapeutic efficacy of the drug
- 9. Bioavailability Studies • Bioavailability studies are designed to determine either an absolute BA or relative BA. • They can be used to compare different route of administration. • Ex: oral versus IV, IP versus IM. • Drawbacks - ➢ Disease state, other drugs etc. modify the drug absorption, ➢ Establishing a standard set of conditions necessary for bioavailability study is difficult with patients as volunteer