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Formulation factors affecting drug absorption
1. ManipalCollegeofPharmaceuticalSciences(MCOPS)
F O R M U L AT I O N FA C TO R S
A F F E C T I N G D R U G
A B S O R P T I O N
P R E S E N T E D B Y : S H I K H A Y. S I N G H
U N D E R T H E G U I D A N C E O F : D R V A M S H I K R I S H N A T
D E P A R T M E N T O F P H A R M A C E U T I C S
R E G I S T R A T I O N N O . 1 6 0 6 1 7 0 0 9
2. CONTENT
1. Introduction
2. Manufacturing variables
3. Pharmaceutic ingredients
4. Nature and type of dosage form
5. Conclusion
6. References
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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
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6. 2. Method of Granulation
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7. PHARMACEUTIC
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
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8. 1. VEHICLE
Absrption depend to a large extent on its miscibility with biological fluids
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9. 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
2. DILUENTS
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Diluents
Organic Inorganic
10. 3. BINDERS & GRANULATING AGENTS
Promote cohesive compacts before & after compression
Eg polymeric materials like starch, cellulose derivatives, acacia, PVP, etc
4. 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
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11. 5. LUBRICANTS
To aid flow of granules
To reduce interparticle friction
Sticking of particles to dies & punches
Eg Hydrophobic in nature (several metallic stearates & waxes)
6. 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
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12. 7. 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
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13. 8. 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
9. 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
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14. 10. 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
11. CRYSTAL GROWTH INHIBITORS
Eg crystal growth inhibitors like PVP & PEG inhibit conversion of a high energy
metastable polymorph into stable
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15. 12. 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:
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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
16. NATURE & TYPE OF DOSAGE FORM
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17. SOLUTIONS
Solutions is most rapidly absorbed
Drug dissolution is absent
Factors influencing absorption of solution are:
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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
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Surface area
Interfacial tension
Droplet size
Surfactants
Lipophilicity
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19. SUSPENSIONS
Drug dissolution which is generally rapid due to the large surface area of the
particles
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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
particle size
Polymorphism
wettability
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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
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22. TABLETS
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• 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
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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
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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, Page No. 99-128
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The cause is formation of divalent calcium-tetracycline complex which is poorly soluble & thus, absorbable
Dyes have also been found to inhibit micellar solubilization effect of bile acids which may impair the absorption of hydrophobic drugs like steroids. Cationic dyes are more reactive than the anionic ones due to their greater power for adsorption on primary particles.
known to inhibit wettability, penetration of water into tablet and their disintegration and dissolution This is because the disintegrant gets coated with the lubricant if blended simultaneously which however can be prevented by adding the lubricant in the final stage. The best alternative is use of soluble lubricants like SLS and carbowaxes which promote drug dissolution
(acacia, tragacanth, etc),
from oily solutions, emulsions or suspensions of medicaments