BIO-RELEVANT DISSOLUTION MEDIA

INTRODUCTION

Simulation of gastrointestinal conditions is essential to

adequately predict the in vivo behavior of poorlysoluble drugs. Simulating small intestinal conditionswith biorelevant media such as fasted state

simulatedintestinal fluid (FaSSIF) and fed state simulated

intestinalfluid (FeSSIF) has become standard practice in

manydissolution laboratories .

However, due to their complex composition, these media are expensive and, to date, need to be prepared on the day of the experiment.

The aim of the present study was to develop media that

are easier to prepare and are stable over a longer period, but can still serve the purpose of forecasting in vivo performance.

Criteria for developing simplified test media also include cost-effectiveness and the ability to adequately reflect the physicochemical properties of the bio relevant media FaSSIF or FeSSIF .

The aim of the present study was to develop media that

are easier to prepare and are stable over a longer period, but can still serve the purpose of forecasting in vivo performance.

Criteria for developing simplified test media also

include cost-effectiveness and the ability to adequately reflect the physicochemical properties of the bio relevant media FaSSIF or FeSSIF

PREPARATION OF BIORELEVANT MEDIA

MATERIALS Brij® 35 (polyoxyethyleneglycol dodecyl ether) Span® 80 (sorbitan monooleate) Tween® 20 (polyoxyethylene sorbitan

monolaurate) Tween® 40 (polyoxyethylene sorbitan monopalmitate)

Tween® 60 (polyoxyethylene sorbitan monostearate)

Tween® 80 (polyoxyethylene sorbitan monooleate)

PREPARATION OF BLANK FaSSIF

Dissolve 1.74 g of NaOH (pellets), 19.77 g of NaH2PO4.H2O or 17.19 g of anhydrous NaH2PO4, and 30.93g of NaCl in

5 L of purified water. Adjust the pH to exactly 6.5 using 1 N NaOH or 1 N HCl.

PREPARATION OF FaSSIF

Dissolve 3.3 g of sodium taurocholate in 500 mL blank

FaSSIF. Add 11.8 mL of a solution containing 100 mg /ml

lecithin in methylene chloride, forming an emulsion. The methylene chloride is eliminated under vacuum

at about 40°C. Draw a vacuum for fifteen minutes at 250 mbar, followed by 15 minutes at 100 mbar.

This results in a clear,micellar solution, having no perceptible odor of methylene chloride.

After cooling to room temperature, adjust the volume to

2 L with blank FaSSIF. For dissolution tests a volume of 500 mL is

recommended.

PREPARATION OF BLANK FeSSIF

Dissolve 20.2 g of NaOH (pellets), 43.25 g of glacial acetic acid, and 59.37 g of NaCl in 5 L of purified

water Adjust the pH to exactly 5.0 using 1 N NaOH or 1 N HCl.

PREPARATION OF FeSSIF

Dissolve 16.5 g of sodium taurocholate in 500 mL of blank FeSSIF. Add 59.08 mL of a solution containing 100mg/mL lecithin in methylene chloride, forming an

emulsion. The methylene chloride is eliminated under

vacuum at about 40°C. Draw a vacuum for fifteen minutes at

250 mbar, followed by 15 minutes at 100 mbar. This results in a clear to slightly hazy,micellar

solution having no perceptible odor of methylene chloride.

After cooling to room temperature, adjust the volume to 2 L with blank FeSSIF.

The recommended volume for simulating conditions in

the upper small intestine after a meal is one liter.

PHYSICAL CHEMICAL EVALUATION OF THE MEDIA

The pH of all test media was measured with a pH meter. The buffer capacity was quantified by potentiometric titration with 0.1 N hydrochloric acid. The osmolality was measured by semi-micro osmometry

(osmometer type Surface tension was determined with a bubble-pressure tensiometer

PHYSICO CHEMICAL PARAMETERS OF THE TEST MEDIA: TARGET VALUES AND TOLERANCES

SIMULATED FeSSIF SIMULATED FaSSIF

Parameter target value range of tolerance target value range of tolerance pH 6.5 ± 0.1 5.0 ± 0.1

Osmolality [mOsmol/kg] 270 ± 15 670 ± 15 Buffer capacity [mEq/pH/L] 12 ± 2 72 ± 2 Surface tension [mN/m] 54 ± 2 48 ± 2

BIO-RELEVANT MEDIUM

HCl (mL) 1.4 mL (conc. 12N HCl)

NaCl (g) 2.0 g (34.2 mM)

Deionized water 1 L

Na Taurocholate 1.61 g (3 mM)

Lecithin 0.56 g (0.75 mM)

KH2PO4 3.9 g

KCl 7.7 g

NaOH qs pH 6.5

Deionized water 1 L

Fasted Simulated Small Intestinal Fluid (FaSSIF)1

Simulated Gastric Fluid (SGF)

MEDIA PREPARATION

The biorelevant media FaSSIF and FeSSIF were prepared on the day of the experiment. FaSSIF was prepared as follows:

3.3 g sodium taurocholate was dissolved in approximately 500 mL of the blank FaSSIF.

The weight of this mixture was checked and noted (“weight 1”).

Then 11.8 mL of a methylene chloride solution containing 100 mg/mL lecithin (= 1.18 g lecithin, “weight 2”) was added.

This produced an emulsion (i.e., the resulting product was turbid).

The methylene chloride was then evaporated under vacuum using a Rotavap at a temperature of about 40 °C. About 10 min at 500 mbar followed by 30 min at about 50 mbar led to complete removal of the methylene chloride.

The result was a clear, micellar solution having no perceptible odor of methylene chloride. After cooling to room temperature, the weight of the solution was checked again.

The water lost to evaporation was replaced with demineralized water to obtain a total weight corresponding to the sum of “weight 1” and “weight 2.”

Finally, the volume was brought to 2 L with blank FaSSIF.

Likewise, FeSSIF was prepared by first dissolving 16.5 g sodium taurocholate in 500 mL of blank FeSSIF, checking and noting the weight (“weight 1”).

Subsequently, 59.1 Ml of a methylene chloride solution containing 100 mg/mL lecithin (= 5.91 g lecithin, “weight 2”) was added, resulting in an emulsion.

The methylene chloride was then evaporated under the conditions described for FaSSIF until a clear, micellar solution with no perceptible odor of methylene chloride was obtained.

After cooling to room temperature, the weight of the solution was checked again, and the water lost to evaporation was replaced with demineralized water to obtain a total weight corresponding to the sum of “weight 1” and “weight 2.”

Finally, the volume was brought to 2 L with blank FeSSIF.

These methods of manufacturing FaSSIF and FeSSIF

differed slightly from those proposed in the literature (11,12)

Simplified media containing different types and amount

of surfactants were prepared using blank FaSSIF and FeSSIF (i.e., the relevant buffers without sodium taurocholate and lecithin) as the basis. After the surfactant(s) were added, the media were

placed in the ultrasonic bath for 15 min and then stirred for another 15 min on a magnetic stirrer.

Subsequently, various physicochemical parameters such as pH, surface tension, critical micelle concentration, osmolality, and buffer capacity were measured and compared with those of the biorelevant media.

Challenges in early phase formulation development Dissolution in Bio-relevant media Simulated Gastric Fluid (SGF) and Fasted Simulated

Small Intestinal Fluid (FaSSIF) Medium Simple two-stage dissolution model (SGF followed by

FaSSIF)for weak acids and weak bases Five Merck case studies of using dissolution in bio-

relevant medium to guide formulation selection Conclusions Dissolution in bio-relevant medium can be a useful

tool for early formulation selection IVIVR established can be leveraged for future

formulation development and QC method development

ROLE OF BIORELEVANT MEDIA IN FORMULATION DEVELOPMENT

CHALLENGES IN EARLY PHASE FORMULATION DEVELOPMENT

Majority of the drug candidates have poor aqueous solubility

Early phase formulation needs to maximize bioavailability to ensure that API is delivered to the intended target

Variety of formulations options available Limited API and limited formulation materials In-vitro dissolution, if reflecting in-vivo performance,

can be used to guide formulation development

DESIRED DISSOLUTION FOR EARLY PHASE

Traditional Dissolution Desired Dissolution forVolume 500mL to 900mL Smaller volume

medium Aqueous or surfactant Bio-relevant medium: SGF, FaSSIF,

medium with 3-10X sink FeSSIF

Profile Complete release in 60min Relative release rate, ranking order

Detection HPLC or UV (online, offline) Real time measurement Focus on Bio-relevant Method and optimize formulation bioavailability Focus on performance checking (QC) method Bio-relevant media are designed to simulate gastrointestinal

conditions, and provide a higher probability of success in establishing in-

vitro and in-vivo relationships

CASE 1: FORMULATION DEVELOPMENT FOR A LOW SOLUBLE NEUTRAL COMPOUND

Compound A is a neutral compound. Aqueous solubility is < 0.01mg/mL in both SGF and FaSSIF

BCS II with high permeability Various formulations were developed for Phase I

LFC 1-3 with various lipid-surfactant vehicles Two Solid dosage forms with different type of

surfactants Bench-mark of safety assessment formulation Formulations are evaluated in bio-relevant medium (FaSSIF)

CASE 2: BIO-RELEVANT DISSSOLUTION IS MORE DISCRIMINATING

Formulation AUC0-24hr(μM*hr)

Cmax(μM)

Formulation-1 82.1 10.9

Formulation-3 69.1 10.3

Formulation 1 and 2 (filler type 1)have faster release thanformulation-3(filler type 2)in FaSSIF medium

Formulation-1 has slightly Higher bioavailability than formuation-3,correlate with in-vitro results in biorelevantmedium

In-vivo Animal PK result

CASE STUDY 3: FORMULATION SELECTION WITH 2-STAGE BIO RELEVANT DISSOLUTION

Dissolution was conducted in

90mL SGF and 180mL of FaSSIF

with USP II paddle (100rpm) The safety formulation

(10%tween) remain supersaturated

inSGF and Tween Solid formulation A has thehighest release in SGF and

FaSSIF In-vivo animal study showed

that solid formulation A has slightly lower, but comparable exposure to safety formulation

CASE STUDY 5: FORMULATION SELECTION IN FaSSIF MEDIUM

Dissolution was conducted in 500mL of FaSSIF medium

withUSP II paddle (100rpm) Formulation A and B release much faster than formulation

C In-vivo animal study confirm

the same ranking order observed invitro

Surfactant A was selected over

surfactant C

A SIMPLE DISSOLUTION MODELSGF OR FaSSIF

Target Concentration= projected efficacious dose/volume of bio-relevant medium

INVIVO

BIO -RELEVANT MEDIUM VOLUME ADJUSTED BASED ON FORMULATION AVAILABILITY AND TARGET CONCENTRATION

Micro Dissolution USP II Paddle

4-20 mL

200mL 1L

Vessel Type Volume Agitation

Micro Dissolution 4-20mL Stir bar

Vankel 200mL 50-200mL Paddle

Vankel 1000mL 250-1000mL Paddle

CONCLUSION

Selected media containing synthetic surfactants with

physicochemical properties similar to those of FaSSIF and FeSSIF were identified.

These can be used to replace biorelevant test media for screening formulations if it can be shown that solubility and dissolution of the drug in these simplified media are similar to the profiles in biorelevant media prepared with bile components.

BIBILOGRAPHY

1. Dressman, J. B., Reppas, C. – In vitro-in vivo correlations for lipophilic, poorly water-soluble drugs. B.T.Gattefosse, 93: 91–100, 2000.

2. Nicolaides, E., Symillides,M., Dressman, J. B., Reppas, C.– Biorelevant dissolution testing to predict the plasma of lipophilic drugs after oral administration. Pharm. Res., 18(3): 380–388, 2001.

3. Horter,D.,Dressman, J. B. – Influence of physicochemical properties on dissolution of drugs in the gastrointestinal tract. Adv. Drug Del. Rev., 46: 75–87, 2001.

4. Lobenberg, R., Kramer, J., Shah,V. P., Amidon, G. L.,Dressman, J. B. – Dissolution testing as a prognostic tool for oral drug absorption: Dissolution behavior of glibenclamide. Pharm. Res., 17: 439–444, 2000.