INTRODUCTION MANNITOL : mainly used as bulking agent and cryoprotectant. CRITERIA FOR USING BULKING AGENT: API<2% ADVANTAGE : When formulation frozen slowly produce crystals which supports API and prevent loss of product USUALLY NON-REACTIVE WITH ACTIVE CONSTITUENT Provides more stable cake of API as compared to lactose DISADVANTAGE: Mannitol interacts with proteins and forms turbid and hazy solution on storage
Selection of excipient depends on interaction with API . Mannitol is a hexahydric alcohol that has been extensively used as an excipient for the freeze drying of pharmaceuticals Mannitol differs from other cryo- or lyo-protectant in that it tends to recrystallize on drying, supposedly via eutectic formation with water in contrast to the behavior of materials such as sucrose and trehalose that form amorphous products after completion of the drying process.
STRUCTURAL BEHAVIOUR Mannitol is believed to exist in three forms designated as α, β, and δ δ polymorph has loose carbon backbone but strong H-bond β polymorph has strong C-backbone but weak H-bond Polar -OH group of water breaks strong H-bonding of δ polymorph and leads to convert to stable β form.
MANNITOL Polymorph formation depends on protocol and conc. Of mannitol used. Parameters: Ice crystal nucleation temp. and cooling rate Nucleation at higher temp gives stable compound Tn: -2.6oC gives 60%wt stable β product Nucleation at lower temp. less stable compound Tn: -7.8oC gives only 2% stable product Cooling rate plays crucial role Fast rate: low stability (-2oC/min) Slow rate: High stability(-0.5oC/min)
PROCESS VARIABLES Effect of conc. Variation: 1.5%, 3%w/w yields β form where as higher conc. Like 7.5%,10% yields mix α,β form.This 10% system after fast cooling gives δ form. Effect of Annealing temp.:annealing step i.e slow rate of cooling temp. is essential for 100% crystalinity With increase in conc. From 1.5,3,5,7,10% w/v amount of crystaline product increase Annamolus behaviour of mannitol: Unlike all other sugars in thermodynamic graph of mannitol 3% solution through DSC plot cooling from 10 o showed exotherm at -21o followed by smaller isotherm at -29o.But degree of reproducibilty was -24o
Why could this problem have occurred? This problem could be due to formation of β polymorph which has low solubility due to its crystalline nature This problem may even divert to interaction between mannitol and API if the anti cancer drug is protenious in nature The other possibility is crystallization of buffer used such as sodium acetate in our case which crystalise during freeze drying but form complex which has low probability of hydration
Do you think this problem is due to Mannitol? Yes this problem is mainly concentrated to dynamic polymorphic nature of Mannitol Rapid transformation from meta stable α, δ polymorphic form to stable β form which is crystalline in nature and driven by moisture
PARAMETERS Process variables:1. Freezing rate2. Annealing temperature (for Mannitol is -29 o C)3. Secondary drying temperature Product responses:1. Ice crystalization temperature2. Onset and duration of mannitol crystalization3. Cooling rate4. Duration of primary drying5. Residual moisture content
Approaches for prevention of fibers Solvent used for mannitol freeze drying process is mixture of acetone/ water Mannitol is not soluble in acetone and its stability is 6 months This approach will help to produce and preserve δ polymorph which is amorphous in nature and hence will resolve the fibre problem if it is due to crystaline nature of β polymorph
2nd Approach For the increase in stability of protein drugs using a mixture of excipient like mannitol/sorbtol and mannitol/trehalose . In the mannitol/sorbitol co-solute systems the spray dried samples containing lysozyme and trypsin showed a decrease in stability with an increase in sorbitol content of the initial sample. The enzymatic assays revealed that addition of sorbitol to the initial mixture caused a decrease in retained activity immediately after production and after storage for four weeks at 75% RH and 40°C. Loss of structural integrity was confirmed from Raman data. Co-spray drying the proteins with trehalose/mannitol gave a higher retained activity both before and after exposure than the mannitol/sorbitol samples.
ANNALYTICAL APPROACHSCANNING ELECTRON MICROSCOPY HELPS TO STUDY MORPHOLOGICALNATURE OF CRYSTALS Scanning electron-micrographs of δ-crystal; (a) before, (b) after exposure to 97%RH for 20 h
XPRDX-ray diffraction patterns of mannitol samples; (a) recrystallisedsample, (b) commercial product.Referential X-ray diffraction patterns of polymorphic forms ofmannitol; (a) α form (b) β form, (c) δ form
CONCLUSION FIBER FORMATION CAN BE EITHER PREVENTED BY FORMING AND PRESEVING AMORPHOUS STAGE WHICH HAS SOLUBILITY IN AQUEOUS STATE BY FORMING COSOLVENTS SUCH AS MANNITOL/TREHALOSE IS FOUND TO BE SUCCESFUL BY ARRANGING DESSICANT IN VIAL STOPPER SO THAT IT MAINTAIN DESIRED MOISTURE LEVEL SO THAT δ POLYMORH IS PRESEVED
REFERENCE1. International Journal of Pharmaceutics Volume 247, Issues 1-2, 24 October 2002, Pages 69-77.2. Chemical Engineering Research and Design Volume 87, Issue 8, August 2009, Pages 1017-10273. Lyophilization Introduction and basic principles,Thomas Jenning4. JOURNAL OF PHARMACEUTICAL SCIENCES, VOL. 92, NO. 9, SEPTEMBER 20035. T. Yoshinari1, R. T. Forbes1, M. Mercer2, P. York1 1University of Bradford: Bradford, United Kingdom ; 2Hiden Analytical Ltd.: Warrington, United Kingdom6. R. forbes1, W. hulse1, M. bonner1, S. burgess27. pharmacy, university of bradford, 2merck speciality chemicals, merck uk