bioavailability

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In vitro drug dissolution rate and bioavailability : 

In vitro drug dissolution rate and bioavailability Factors to be considered: Factors relating to dissolution apparatus Factors relating to dissolution fluid Process parameters

Ideal features of dissolution apparatus : 

Ideal features of dissolution apparatus Simple in design Fabrication dimensions are specified and reproducible Easy introduction of dosage Controlled, uniform, non-turbulent liquid agitation Minimum mechanical abrasion Maintain sink conditions Eliminates evaporation Ease to draw samples Facilitates good laboratory equipment Sensitive to reveal process changes Permits evaluation of disintegrating, non-disintegrating, dense, floating tablets or capsules etc.

Types of dissolution apparatus : 

Types of dissolution apparatus Closed compartment Open compartment Official compendial methods: Rotating basket Rotating paddle Reciprocating cylinder Flow-through cell Paddle over disc Cylinder apparatus Reciprocating disc

Dissolution acceptance criteria : 

Dissolution acceptance criteria Q is defined as percentage of drug content dissolved in a given time period.

Objectives of dissolution profile comparison : 

Objectives of dissolution profile comparison Development of bioequivalent drug products. Demonstrating equivalence after change in formulation of drug product. Biowaiver of drug product of lower dose strength in proportion to higher dose strength product containing same active ingredient and excipients.

Method for comparison of dissolution profile : 

Method for comparison of dissolution profile Based on the determination of difference factor f1 and similarity factor f2

In Vitro-in vivo correlation : 

In Vitro-in vivo correlation A predictive mathematical model that describes the relationship between an in-vitro property of a dosage form and an in-vivo response.

Basic approaches : 

Basic approaches By establishing a relationship usually linear, between the in vitro dissolution and in vivo bioavailability parameters. By using data from previous bioavailability studies to modify the dissolution methodology.

In vitro-in vivo correlations : 

In vitro-in vivo correlations Correlations based on the plasma level data Correlations based on the urinary excretion data Correlations based on the pharmacological response

IVIVC levels : 

IVIVC levels Level A: Point to point correlation is developed between in vitro dissolution rate and the in vivo rate of absorption Level B: Utilises statistical moment analysis and the mean in vitro dissolution time is compared to either the mean residence time or the mean in vivo dissolution time Level C: single point correlation that relates one dissolution time point to one pharmacokinetic parameter Multiple level C

Applications : 

Applications Ensure batch to batch consistency Serve as a tool in the development of a new dosage form with desired in-vivo performance Assist in validating or setting dissolution specifications

The Biopharmaceutics Classification System (BCS) Guidance : 

The Biopharmaceutics Classification System (BCS) Guidance

Slide 15: 

Purpose of the BCS Guidance:  Expands the regulatory application of the BCS and recommends methods for classifying drugs. Explains when a waiver for in vivo bioavailability and bioequivalence studies may be requested based on the approach of BCS.

BCS Classifications : 

BCS Classifications According to the BCS, drug substances are classified as follows: Class I - High Permeability, High Solubility Class II - High Permeability, Low Solubility Class III - Low Permeability, High Solubility Class IV - Low Permeability, Low Solubility

Bioequivalence studies : 

Bioequivalence studies Objective If there is a risk of bio-inequivalence or There is a risk of pharmacotherapeutic failure or diminished clinical safety

Slide 21: 

What is equivalence? Chemical equivalence Pharmaceutical equivalence Bioequivalence Therapeutic equivalence

Types of bioequivalence studies : 

Types of bioequivalence studies In vivo Oral immediate release products Non-oral immediate release products Modified release products

In vitro bioequivalence : 

In vitro bioequivalence The drug product differs only in strength of the active substance The drug product has been slightly reformulated or manufacturing method has been slightly modified An acceptable IVIVC and the in vitro dissolution rate of new product is equivalent with that of the already approved medicinal product

Bioequivalence experimental study design : 

Bioequivalence experimental study design Complete randomised designs Randomised block designs Repeated measures, cross over and carry over designs Latin square designs Method of randomisation Advantages Disadvantages

Bioequivalence study protocol : 

Bioequivalence study protocol

Statistical interpretation : 

Statistical interpretation ANOVA Confidence interval approach

Methods for enhancing bioavailability : 

Methods for enhancing bioavailability Aqueous solubility or dissolution rate Permeability

Bioavailability enhancement through enhancement of drug solubility or dissolution rate : 

Bioavailability enhancement through enhancement of drug solubility or dissolution rate Micronization Nanonisation Supercritical fluid recrystallization Spray freezing into liquid Evaporative precipitation into aqueous solution Surfactants Salt forms Precipitation inhibitors Alteration of pH Amorphs, polymorphs, solvates Solvent deposition Precipitation Selective adsorption Solid solutions Eutectic mixtures Solid dispersions Molecular encapsulation with cyclodextrins

Bioavailability enhancement through enhancement of drug permeabiliy across biomembrane : 

Lipid technologies Ion pairing Penetration enhancers Bioavailability enhancement through enhancement of drug permeabiliy across biomembrane 1.Lipid solutions and suspensions 2.Coarse emulsions 3.Solid lipid nanoparticles 4.Nanostructured lipid carriers 5.Lipid-drug conjugate 6.Liposomes

Bioavailability enhancement through enhancement of drug stability : 

Enteric coating Complexation Use of metabolism inhibitors Bioavailability enhancement through enhancement of drug stability Bioadhesive delivery system Controlled release microencapsulated system Immobilisation of enzyme inhibitors

Bioavailability enhancement through gastrointestinal retention : 

Increased contact with epithelial surface Prolonging residence time in the stomach Delaying intestinal transit Bioavailability enhancement through gastrointestinal retention

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