1. Gastrointestinal Absorption: Role of the Dosage Form
Bioavailability
Solution>suspension>capsule>tablet>coated tablet

4. Solution: drugs that are water soluble and stable in aq solution
Eliminates in vivo dissolution step
Rate limiting step in abs.
Weak acidic drug, administered as salt
Solubility of poorly soluble drug

5. Suspensions: insoluble or poorly soluble drugs
Absorption rate is dissolution rate limited, however
Particles diffuse rapidly through the GIT
Dissolution starts immediately
Factors to be considered in the formulation of a suspension
Particle size (surface area)
Crystal form and polymorphism
Complexation
Wetting agents
Viscosity

6. Hard gelatin capsules
Bioavailability is better than a compressed tablet
Overall rate of dissolution:
Dissolution rate of the shell
Rate of penetration of GI fluids into the encaps. Mass
Rate of mass deaggregation
Rate of dissolution of the dispersed mass
Hydrophilic excipients
Wetting agents
Lubricants
Formulation and type of filling process

8. Formulation factors that might influence the bioavailability of capsules
Surface area and particle size of the drug
Crystal form
Nature and quantity of diluent, lubricant and wetting agent
Drug-excipient interactions
Filling process
Packing density of the powder
Type and composition of the shell (enteric shell)
Interactions between shell and capsule components

9. Soft gelatin capsules
Combine the convenience of unit dosage form with rapid abs of liquids and suspensions
Drug is dissolved or dispersed in a non-toxic non-aq vehicle
Drug release: water miscible vehicle
water immiscible vehicle
Formulation factors to be taken into consideration
Solubility of the drug in the vehicle
Particle size of the drug
Nature of the vehicle
Inclusion of surfactant, emulsifying agent
Complexation

10. Tablets
Most widely used dosage form
Produced by wet granulation or direct compression
Bioavailability problems: reduction of SA and generation of well disp. drug particles
Formulation factors: Lubricants
Compression force (tablet hardness)

12. Coated tablets
Sugar coating, film coating
Sugar coating: sealing: shellac, cellulose acetate phthalate
Film coating:
Water miscible: hydroxypropyl methycelullose, carboxymethylcellulose
Water insoluble: ethylcellulose, acrylic resins

13. Press coated tablets
Enteric coated tablets
Special film coat that resists gastric fluids
Polymers: cellulose acetate phthalate, hydroxypropyl methylcellulose phthalate and polyvinyl acetate phthalate

14. DISSOLUTION AND DRUG RELEASE TESTING
Dissolution and drug release tests are in-vitro tests that measure the rate and extent of dissolution or release of the drug substance from a drug product, usually in an aqueous medium under specified conditions.
The dissolution test is an important quality control procedure for the drug product and is often linked to product performance in vivo.
In-vitro drug dissolution studies are most often used for monitoring drug product stability and manufacturing process control.

15. As a quality control test, dissolution and drug release testing may be used for:
Batch-to-batch drug release uniformity
Stability
Scale-up and postapproval changes (SUPAC)
Predicting in-vivo performance

16. Dissolution Conditions
The development of an appropriate dissolution test requires the investigator to try different agitation rates, different media (including volume and pH of medium), and different kinds of dissolution apparatus.
Once a suitable dissolution test is obtained, acceptable dissolution criteria are developed for the drug product and its formulation.
These criteria or dissolution specifications (eg, percent of drug dissolved in 30 minutes) are used to investigate formulation problems.

17. COMPENDIAL METHODS OF DISSOLUTION