Lecture 1: Oral Dosage Forms Flashcards
Oral Dosage forms
-tablets
-capsules
-orally dissolving tablets (ODT)
-sublingual tablets
-solutions
-suspensions
Tablets
-immediate, extended, modified release
-effervescent, chewable, sublingual
Effervescent tablets
-uncoated
-generally contain acid substances, carbonates, or bicarbonates
-release CO2 in water
-designed to be dissolved in water before use
Chewable tablets
-designed for admin to children
Buccal/sublingual tablets
-place under tongue or cheek
-dissolve rapidly
-absorbed through mucus membranes into blood stream
Capsules
-meds in a gelatin container
-hard-shelled or soft-shelled
hard-shelled capsules
-used for dry, powdered ingredients
soft-shell capsules
-used for oils and active ingredients dissolved/suspended in oil
Advantages of soft capsules
-drug can be liquid form
-high degree of precision in each dose
-higher degree of homogeneity
-rapid release
Disadvantages of soft capsules
-drug may migrate to the shell
-drug can degrade in liquid state
Oral Liquid dosage forms
-solutions
-emulsions
-suspensions
-syrup
oral solutions
-clear liquid preparations conaining API in suitable vehicle
Oral emulsions
-stabilized in oil-in-water dispersions
-either or both phases may contain dissolved solids
Oral suspensions
-contain API suspended in solvent
-may show sediment over time
-need to be shaken
syrup
-concentrated solution of sucrose to mask taste
Advantages to oral dosage forms
-convenient
-economical
-non-invasive
-no special training
Disadvantages to oral dosage forms
-drug delivery often incomplete
-many drugs degraded in GI environment
-exposes drug to hepatic metabolism
Oral absorption
-disintegration
2. dissolution
3. absorption or gut-wall first pass metabolism
4. hepatic first-pass metabolism
5. rest of drug to circulation
Dissolution increases with
-surface area
-solubility
-concentration
-DEcreased membrane thickness
-Noyes-Whitney equation
Where does most absorption occur
-small intestine
-surface area same as tennis court
Bioavailability
-relative fraction of dose that is absorbed to circulation
-100% in IV
DEcrease bioavailability by:
-incomplete dissolution
-chemical degradation of drug in GI tract
-first-pass gut wall metabolism
-first-pass hepatic metabolism
First-pass effect
-loss of drugs by degradation in GI tract or hepatic metabolism
-reduced amount of drug BEFORE entering circulation
Grapefruit juice
-inhibits first-pass effect of drug in intestine and liver
-increases bioavailability
Noyes-Whitney equation
dissolution rate = A*D(Cs-CT)/h
-A= area
-D= diffusion coefficient
-Cs= solubility
-Ct = concentration
-h= layer thickness
