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FORMULATION FACTORS

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allelipraise's version from 2017-09-17 17:48

Section 1

Question Answer
FORMULATION FACTORS• Physicochemical Properties • Dosage Form
Drug SolubilityStatic (equilibrium) property in a saturated solution
Drug Solubilitydissolution of solute in solvent to give a homogenous system
Particle Size• Inversely related to surface area • Dissolution rate directly related to surface area • Micronization
Partition coefficientdefined as a ratio of the drug concentration in the oil phase to the drug concentration in the aqueous phase
Partition coefficientHydrophilic Drugs* • Hydrophobic Drugs*
Extent of ionizationDependent on the pKa of weak electrolyte and the pH of the solution
Extent of ionizationfraction of a weak electrolyte (acid or base) that dissociates in solution
Chemical VariationSalt formation, ester formation
Chemical VariationTo provide slower dissolution, slower absorption and longer duration of action
Chemical VariationSelected for greater stability, less local irritation at the absorption site or less systemic toxicity
Weak acids: water-soluble forms are K+ and Na+ salts
Weak base:water-soluble forms are HCl, SO4, citrate, gluconate, tartrate, succinate
PolymorphismAbility of drug to exist in more than one crystalline forms
Crystalline definite identifiable shape
PolymorphismDifferent polymorphs have different physical properties (MP, BP, dissolution rate)
Amorphous no definite structure
PolymorphismInsulin, Pen G
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Section 2

Question Answer
ChiralityAbility of the drug to exist as optically active stereoisomers or enantiomers
ChiralityEach enantiomer behave differently pharmacokinetically and pharmacodynamically
RACEMICChiral drugs _______mixtures
Chiralitydrugs exist in r-s enantiomers
S- enantiomer pharmacologically active
R- enantiomer undergoes presystemc inversion in the gut to S-
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Section 3

Question Answer
Dosage Formcomplicated the formulation of the finished drug product the greater the potential for absorption problem”
slowest stepRate-limiting step in the absorption of the drug is the _________ in the series of processes
gastric emptyingRate limiting step is the rate of (LIQUID DOSAGE FORM)
finely divided precipitatesA drug in hydroalcoholic solutions has good absorption but may tend to form____________in the lumen of GIT
Viscosity_______may interfere with dilution and mixing with GIT contents
EMULSIONSInherently unstable (droplets tend to coalesce)*
EMULSIONSprevents coalescence and maintains the integrity of the individual droplets
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Section 4

Question Answer
SUSPENSIONSFinely divided powder dispersed in viscous medium • Surface active* • Viscosity*
• Liberation • Dissolution • ConvectionandDiffusion • AbsorptionAbsorption of the drug from an oral solid dosage form depends on a succession of processes
Conventional oral dosage forms: Rate-limiting step is dissolution
Modified-release forms:Rate-limiting step is liberation
HARD SHELL CAPSULES filled with a powder blend
HARD SHELL CAPSULESContents should not be subjected to high compression forces • Dispersing agent will minimize aggregation and maximize the surface area of the powder • Should disrupt rapidly and allow the contents to mix with GIT contents
SOFT SHELL CAPSULEMay contain a non-aqueous solution, a powder or a drug suspension with a vehicle that is water-miscible (PEG) or hydrophobic (vegetable oil)
SOFT SHELL CAPSULEDrugs in hydrophobic vehicle have poorer absorption than in compressed tablets
TABLET Solid dosage form containing the drug and excipients and usually compressed into a solid mass
TABLETDrug release is affected by excipients
reduction of surface area(Disadvantage of SOlid dosage)
Excipients: • Bulking agent • Granulating agent • Disintegrant • Wetting agent, surfactant • Anti-frictional agentExcipients: Tablet
COATED TABLETScoating must breakdown quickly
Sugar/Film CoatedTypes of Coated Tablet
COATED TABLETS(Advantage)Protect the drug from moisture, light and air
COATED TABLETS(Advantage)Mask the taste or odor of the drug
COATED TABLETS(Advantage)Improve the appearance of the tablet
COATED TABLETS(Advantage)Affectreleaserateof the drug
MODIFIED RELEASE TABLETSHave altered rate or timing of drug release
MODIFIED RELEASE TABLETSER/DR ex Enteric Coated
MODIFIED RELEASE TABLETS(Advantage)Advantages • Less frequent dosing and better compliance • Reduced variations in plasma level
MODIFIED RELEASE TABLETS(Disadvantage)• More complicated formulation • Dose dumping problem • More expensive technology
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Section 5

Question Answer
Transdermal Drug Delivery Systems(Components)Occlusive impermeable backing/Formulation matrix/Adhesive layer
Occlusive impermeable backingPrevents insensible water loss from the skin
Occlusive impermeable backingEnchances permeation of the skin by the drug
Formulation matrixMaintains the drug conc. within the device
Formulation matrixResults to drug partitioning and diffusion into skin
Adhesive layerEnsures drug contact with the skin and continued drug delivery
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Section 6

Question Answer
TARGETED (SITE-SPECIFIC) DRUG DELIVERY SYSTEMSSystems that place the drug at or near the receptor site by complexing with a carrier that recognizes the target
TARGETED (SITE-SPECIFIC) DRUG DELIVERY SYSTEMSCapillary bed of the active site
TARGETED (SITE-SPECIFIC) DRUG DELIVERY SYSTEMSSpecial type of cell (tumor cells) but not to normal cells
TARGETED (SITE-SPECIFIC) DRUG DELIVERY SYSTEMSSpecific organ or tissue
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Section 7

Question Answer
INSERTS, IMPLANTS AND DEVICESDrug is impregnated into a biodegradable or non- biodegradable material and inserted in the body
INSERTS, IMPLANTS AND DEVICESDrug is released slowly for localized or systemic effect
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Section 8

Question Answer
drugs affect the motility of the GITDecreased GI motility by TCA and antipsychotics
drugs affect the motility of the GITReduced stomach acid secretion by anticholinergics
drugs affect the motility of the GIT Some drugs interfere with the absorption of other drugs
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Section 9

Question Answer
PATHOLOGIC FACTORS:Presence of disease such as:• Diarrhea • Constipation • Parkinson’s
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