This document discusses factors that influence drug absorption from various pharmaceutical dosage forms. It outlines several formulation variables like excipients, manufacturing processes, dosage form characteristics, and drug properties that can impact the dissolution and absorption of drugs. These variables include excipient type and amount, particle size, polymorphism, compression force, method of granulation, viscosity, and surface area. The document also examines how these factors influence drug absorption from different dosage forms like tablets, capsules, solutions, emulsions, and powders. Understanding these variables is important for developing formulations that effectively deliver drugs to systemic circulation.

1. BY SAYEDA SALMA
1ST M PHARM
DEPT OF PHARMACEUTICS

2. INDEX
› Introduction
› Manufacturing variables
› Pharmaceutical ingredients/excipients
› Nature and type of dosage form
› Conclusion
› References

3. INTRODUCTION
› A drug injected intravascularly directly enters systemic
circulation & exerts its pharmacological effects.
› If intended to act systemically, such drugs can exert their
pharmacological actions only when they come into blood
circulation from their site of application.
› Majority of drugs are administered extravascular only.
› Absorption is an important step.

4. PROCESSING FACTORS
DOSAGE FORM
DISSOLUTION
ABSORPTION
VARIABLES
EXCIPIENTS
MANUFACTURING
PROCESS

5. MANUFACTURING PROCESSES
› Manufacturing processes that influence drug dissolution are:
1. Compression force
* density
* porosity
* hardness
* disintegration time
* dissolution of tablets

6. METHOD OF GRANULATION

7. PHARMACEUTICAL INGREDIENTS/EXCIPIENTS
› Despite their inertness & utility in the dosage form, excipients can
influence absorption of drug .
› More number of excipients in a dosage form, the more complex it
is & greater potential for absorption & bioavailability problems
› Excipients are added to ensure ,
1. Stability
2. Uniformity
3. Functionability
4. Bioavailability
5. Acceptability

8. VEHICLE
› Absorption depend to a large extent on its miscibility with
biological fluids.
NON AQUEOUS WATER
MISCIBLE VEHINCLES
NON
AQUEOUS
WATER
IMMISCIBLE
VEHICLES
AQUEOUS
VEHICLES

9. DILUENTS
› Diluents are commonly added to tablet (and capsule)
formulations if the required dose is inadequate to produce the
necessary bulk.
› Eg of drug-diluent interaction resulting in poor bioavailability
is that of tetracycline & DCP
DILUENTS

10. BINDERS & GRANULATING AGENTS
› Promote cohesive compacts before & after compression.
› Eg polymeric materials like starch, cellulose derivatives, acacia,
PVP, etc.
COLOURANTS
› Very low concentration of water-soluble dye inhibitory effect
on dissolution
› Dye molecules get adsorbed onto the crystal faces & inhibit
drug dissolution
› E.g. brilliant blue retards dissolution of sulfathiazole

11. LUBRICANTS
› To aid flow of granules
› To reduce interparticle friction
› Sticking of particles to dies & punches
› Eg Hydrophobic in nature (several metallic stearates & waxes)
COATINGS
› Deleterious effect of various coatings on drug dissolution from a
tablet dosage form is enteric coat > sugar coat > nonenteric film
coat
› E.g. Shellac coated tablets, on prolonged storage, dissolve more
slowly in the GIT

12. DISINTEGRANTS
› Agents overcome cohesive strength of tablet & break them up
on contact with water which is an important prerequisite to
tablet dissolution
› These are hydrophilic in nature. Eg :MCC
› Mechanism-

13. BUFFERS
› They create right atmosphere for dissolution. e.g. buffered
aspirin tablets.
› Buffer containing potassium cations inhibit the drug
absorption. e.g. vitamin B2 & sulphanilamide.
SURFACTANTS
› They may enhance or retard drug absorption.
1. Promotion of wetting & dissolution of drugs
2. Better membrane contact of drug for absorption
3. Enhanced membrane permeability of the drug

14. SUSPENDING AGENTS/VISCOSITY IMPARTERS
› Hydrophilic polymers like vegetable gums, semisynthetic gums
& synthetic gums.
› Stabilize drug particles by reducing their rate of settling & by
increasing viscosity of
› the medium they also affect palatability & pourability of
solution dosage forms. Eg Na-CMC complex amphetamine
increases drug absorption
CRYSTAL GROWTH INHIBITORS
› Eg crystal growth inhibitors like PVP & PEG inhibit conversion
of a high energy metastable polymorph into stable

15. › COMPLEXING AGENTS
› These agent alters stability, solubility, molecular size, partition
coefficient & diffusion coefficient
› Pharmacologically inert & must dissociate either at the
absorption site or following absorption into the systemic
circulation
› Complexation has been used to enhance drug absorption are:
Enhanced dissolution through formation of a soluble
complex e.g. ergotamine tartarate-caffeine complex
Enhanced lipophilicity for better membrane permeability
e.g. caffeine-PABA complex
Enhanced membrane permeability e.g. enhanced GI
absorption of heparin

17. SOLUTIONS
› Solutions is most rapidly absorbed
› Drug dissolution is absent
› Factors influencing absorption of solution are:
1) Viscosity
2) Surfactants
3) Solubilizer
4) Stabilizer
5) stability

18. EMULSIONS
› Superior to suspensions in administering poorly aqueous
soluble lipophilic drugs
› Absorption increases 3 fold over its aqueous suspension
› Factors influencing drug absorption of emulsion are:
1) Surface area
2) Interfacial tension
3) Droplet size
4) Surfactants
5) Lipophilicity

19. SUSPENSION
› Drug dissolution which is generally rapid due to the large
surface area of the particles
FACTORSAFFECTING
ABSORPTION
PARTICLE SIZE
POLYMORPHISM
WETTING AGENTS
VISCOSITY OF THE MEDIUM
SUSPENDING AGENT

20. POWDERS
› Though powders are superior to tablets & capsules
› They are not in use nowadays due to handling & palatability
problems
› Factors to be considered in the absorption of drug from
powders are:
1) particle size
2) Polymorphism
3) wettability

21. CAPSULES
Powders & granules are administered in hard gelatin capsules whereas
viscous fluids & oils in soft elastic shells.
Factors of importance in case of hard gel:
Drug particle size
Density
Polymorphism
Intensity of packing
Influence of diluents & excipients
Factors of importance in case of soft gel:
Between the drug & the diluent
Between drug & gelatin shell

22. TABLETS
Compressed Tablets > Film Coated Tablets > Sugar Coated
Tablets > Enteric Coated Tablets>Sustained Release Products.
Factors to be considered in the absorption of drug from
tablets are:
 Effective surface area
 Area dissolution
 Deaggregation
 Permeability
 Excipients/API
 Type of tablets

23. CONCLUSION
› Absorption plays an major role to attain the desired
therapeutic action with minimal side effects at the given
period of time
› Formulation factors influencing drug absorption helps us to
focus on formulating drug with proper attainment of
permeability of drugs to systemic circulation at given time

24. REFERENCES
1) Brahmankar D.M., Jaiswal S.B., First edition, “Absorption of
Drugs” Biopharmaceutics and Pharmacokinetics – A treatise,
Vallabh Prakashan, Delhi 1995, page no. 27-77
2) Shargel L., Andrew B.C., Fourth edition “Physiologic factors
related to drug absorption” Applied Biopharmaceutics and
Pharmacokinetics, Prentice Hall International, INC., Stanford
1999, PageNo. 99-128