biopharmaceutical classification system

1. Biopharmaceutics classification system , methods of permeability generic biologics , Bioequivalence and bioavailability and generic substitution Department of pharmaceutics Siddhapura Pratik ( M.Pharm Pharmaceutics) Prepared by: Siddhapura Pratik M.Pharm (sem-2)

2. CONTENT Biopharmaceutics classification system Methods of Permeability: In-vitro, In-situ and In-vivo methods Generic biologics (biosimilar drug products) Clinical significance of bioequivalence studies Special concerns in bioavailability and bioequivalence studies Generic substitution Siddhapura Pratik ( M.Pharm Pharmaceutics)

3. Biopharmaceutics classification system 1.1 Introduction 1.2 Factor affecting on biopharmaceutical classification system 1.3 Biopharmaceutical classification system [Classes] 1.4 Application of biopharmaceutical classification system 1.5 Class boundaries 1.6 Biowaiver 1.7 Criteria of biowaiver 1.8 Conclusion Siddhapura Pratik ( M.Pharm Pharmaceutics)

4. 1.1 Introduction • The Biopharmaceutical Classification system was first developed in 1995, by Amidon et & his colleagues. • Definition: • “The biopharmaceutical classification system is a scientific framework for classifying a drug substance based on its aqueous solubility & intestinal permeability & dissolution rate”. • To saved time fast screening is required so drug substances are classified on basis of solubility and permeability. This classification is called as Biopharmaceutical classification system. Siddhapura Pratik ( M.Pharm Pharmaceutics)

5. 1.2 Factor affecting on biopharmaceutical classification system The biopharmaceutical classification system has been developed to provide A scientific approach to allow for to prediction in vivo pharmacokinetics of oral immediate release (IR) drug product by classifying drug compound based on their. Solubility Permeability Dissolution Siddhapura Pratik ( M.Pharm Pharmaceutics)

6. Solubility The maximum amount of solute dissolved in a given solvent under standard condition of temperature, pressure and pH. Solubility is the ability of the drug to be solution after dissolution. The higher single unit dose is completely soluble in 250 ml at pH 1-6.8 (37 ̊C). Siddhapura Pratik ( M.Pharm Pharmaceutics)

7. Permeability Permeability of the drug to pass the biological membrane which is the lipophilic. Permeability is indirectly based on the extent of absorption of a drug substance. Drug substance is considered to be highly permeable , when the extent of absorption in human determined to be 90% or more of administered drug or compare to in vivo reference dose. Siddhapura Pratik ( M.Pharm Pharmaceutics)

8. Dissolution • It is process in which solid substance solubility in given solvent i.e mass transfer from solid surface to liquid phase. • Using USP apparatus I at 100 rpm or USP apparatus II at 50 rpm. • Dissolution media [900 ml]. • 0.1 N HCl or simulated gastric fluid (pH 1.2) without enzyme. • pH 4.5 buffer & pH 6.8 buffer. • Simulated intestinal fluid without enzyme. Siddhapura Pratik ( M.Pharm Pharmaceutics)

9. 1.3 Biopharmaceutical classification system [Classes] Siddhapura Pratik ( M.Pharm Pharmaceutics)

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12. Class I • Ideal for oral route administration. • Drug absorbed rapidly. • Drug dissolved rapidly. • Rapid therapeutic action. • Bioavailability problem not expected for immediate release drug product. • e.g. Metoprolol, propranolol, diltiazem. Siddhapura Pratik ( M.Pharm Pharmaceutics)

13. Class II • Oral route for administration. • Drug absorb rapidly. • Drug dissolve slowly. • Bioavailability is controlled by dosage form and rate of release of the drug substance. • E.g. nifedipine, naproxen. Siddhapura Pratik ( M.Pharm Pharmaceutics)

14. Class III • Oral route of administration. • Drug absorbance is limited. • Drug dissolve rapidly. • Bioavailability is incomplete if drug is not release or dissolve in absorption window. • E.g. cimetidine, metformin , insulin. Siddhapura Pratik ( M.Pharm Pharmaceutics)

15. Class IV • Poorly absorbed orally administration. • Both solubility & permeability limitation. • Low dissolution rate. • Slow or low therapeutic action. • An alternate route of administration may be needed. • E.g. taxol, chlorthiazole, cefexime trihydrate. Siddhapura Pratik ( M.Pharm Pharmaceutics)

16. 1.4 Application of biopharmaceutical classification system To predict in vivo performance of drug product using solubility and permeability measurements. Aid in earliest stages of drug discovery research. To use in biowaiver considerations. For research scientist to decide upon which drug delivery technology to follow or develop. Also for the regulation of bioequivalence of the drug product during scale up and post approval. Siddhapura Pratik ( M.Pharm Pharmaceutics)

17. 1.5 Class boundaries Highly soluble The highest dose strength is soluble in ≤250 ml water over a pH range of 1 to 7.5. The volume estimate – a glassful ( 8 ounce) Highly permeable When the extent of absorption in humans is determined to be ≥ 90% of an administered dose. Rapidly dissolving When ≥ 85% of the labelled amount of drug substance dissolves within 30 minutes using USP apparatus I to II in a volume of ≤ 900ml buffer solutions. Siddhapura Pratik ( M.Pharm Pharmaceutics)

18. 1.6 Biowaiver “in vitro instead of in vivo bioequivalence testing” Definition: It is an exemption from conducting human bioequivalence studies when the active ingredients meet certain solubility and permeability criteria in vitro and when the dissolution profile of the dosage from meets the requirements for an IR dosage form. Siddhapura Pratik ( M.Pharm Pharmaceutics)

19. 1.7 Criteria of biowaiver Rapid and similar dissolution High solubility High permeability Wide therapeutic window Excipient used in dosage form are same as those present in approved drug product Siddhapura Pratik ( M.Pharm Pharmaceutics)

20. 1.8 Conclusion Biopharmaceutical classification system aims to provide regulatory tools for replacing certain bio-equivalence studies by a accurate in vivo dissolution tests. The in vivo pharmacokinetics of drug depends largely on the solutility and permeability. Many laboratories are engaged to find better means to estimates in vivo behaviour of the drug after oral administration by using simple in vitro dissolution tests. Siddhapura Pratik ( M.Pharm Pharmaceutics)

21. 2.Methods of permeability Methods of permeability In Vitro In Situ In Vivo Siddhapura Pratik ( M.Pharm Pharmaceutics)

22. IN VITRO METHOD In vitro method are carried out outside of the body and are used to determine the permeability of drug using live animal tissues. In vitro models have been introduced to assess to the major factors involved in the absorption process and predict the rate and extent of drug absorption. Here, the intestine of lower experimental animals such as rats , guinea pigs, rabbits are taken for the study. Siddhapura Pratik ( M.Pharm Pharmaceutics)

23. The different in vitro methods are: • Physicochemical methods • Partition coefficient • Artificial membranes • Chromatographic retention indices • Brush border membrane vesicles (BBMV) • Isolated intestinal cells • Tissue technique: • Everted small intestinal sac technique • Everted sac modification • Circulation techniques • Everted intestinal ring or slice techniques • diffusion cell method • Cell culture techniques. Siddhapura Pratik ( M.Pharm Pharmaceutics)

24. 1. Partition coefficient Siddhapura Pratik ( M.Pharm Pharmaceutics)

25. 1. Partition coefficient Siddhapura Pratik ( M.Pharm Pharmaceutics)

26. 1. Partition coefficient Partition coefficient between an oil and water phase , log p, is one of the easiest property of a drug molecule that can be determined. It provides a measure of the lipophilicity of a molecule and can be used to predict to what extent it will cross the biological membrane. Eg. Octanol is selected as an oil phase as it has similar properties to biological membranes. It’s important to note that log p does not take the degree of ionization into consideration and hence log D is used. Siddhapura Pratik ( M.Pharm Pharmaceutics)

27. 1. Partition coefficient Log D is the distribution coefficient where aqueous phase is at a particular pH and thus it takes into account the ionization of the molecule at thspH. The log D measured at intestinal pH will givea much better idea about extent of drug permeability across GI membrane than log P. Siddhapura Pratik ( M.Pharm Pharmaceutics)

28. 2. ARTIFICALMEMBRANES • Artificial membranes are very useful in studying passive membrane permeability as they are reproducible and are suitable for high throughput screening. • In this method, PAMPA model isused. Parallel artificial membrane permeability assay(PAMPA) • PAMPA is a method which determines the permeability of substances from a donor compartment, through a lipid infused artificial membrane into an acceptor compartment. • The artificial membrane is like a phospholipid membranes supported by filtermaterial. • It is prepared by pipetting a solution of lipids in an inert organic solvent on a supporting filter material which is placed on 96- well microtitreplate. Siddhapura Pratik ( M.Pharm Pharmaceutics)

29. Procedure • test compound is added to the donor compartment in buffer solution of pH 7.4 and permeation takes place through artificial membrane into the acceptorcompartment. • An aliquot is collected and the concentration of drug permeated is measured by suitable assaytechnique. Siddhapura Pratik ( M.Pharm Pharmaceutics) Fig. Parallel Artificial Membrane Permeationassay(PAMPA)

30. mainly used to determine the intestinalpermeability • Prediction of passivetransport • Trans-cellular permeability ofdrugs Advantage • Used for screening large no. ofcompounds. • Provides information on solubility, lipophilicity and ionization status of adrug. • It is much lesser labor intensive than cell culturemethods. Disadvantage • They are based on approximation and oversimplification of the actual in vivo conditions. Uses Siddhapura Pratik ( M.Pharm Pharmaceutics)

31. A modification ofthissystem is immobilized liposome chromatography(ILC) and on ILC, many compounds with same log P have been shown to demonstrate variable membrane partitioning based on theirlogs. • Liposomes , lipid bilayers produced from mixture of lipids are also useful in investigating passive diffusion of drugs through lipid membranes and also used to study passive absorption of many monocarboxylicacids. • A modified version of this is the filter-immobilized artificial membrane (filter-IAM) permeabilityassay. • This coupled with an instrument PSR4p (Permeability solubility retention, pION, USA) can be used for high throughput permeability screens Siddhapura Pratik ( M.Pharm Pharmaceutics)

32. 3. CHROMATOGRAPHIC RETENTIONINDICES • Immobilized artificial membranes(IAM) chromatography along with physicochemical parameters is used for evaluation of passive intestinal absorption. • IAM packings are prepared by covalently immobilizing monolayers of membrane phospholipids to silicaparticles. • Micellar liquid chromatography(MLC) is also used for the prediction of passive drug absorption and in this system retention of drug mainly depends on hydrophobic, electronic and stericinteractions. • In general, chromatographictechniquesare easy in operation and have high analyticalsensitivity. Siddhapura Pratik ( M.Pharm Pharmaceutics)

33. 4.BRUSH BORDER MEMBRANE VESICLES (BBMV) • A brush border is the name for the microvilli covered surface of simple cuboidal epithelium and simple columnar epithelial cells, found in the smallintestine. • Both animal and human tissue can be used forthis. • Procedure: • intestinaltissuesaretreatedwith calcium chlorideprecipitation method using centrifugation. • the pellets obtained after centrifugation is resuspended in buffer which results in the formation ofvesicles. Siddhapura Pratik ( M.Pharm Pharmaceutics)

34. Fig.2: Structure ofmicrovilli Fig.1: Brush border membranevesicles Siddhapura Pratik ( M.Pharm Pharmaceutics)

35. Vesicles are mixed with drug in buffer solution and filtered after a period oftime • The amount of drug taken up by the vesicles gives an account of drug absorption. Advantage • useful for mechanic studies of drug absorptionprocess. Siddhapura Pratik ( M.Pharm Pharmaceutics)

36. 5. USING ISOLATED INTESTINALCELLS • Here, the small intestine is perfused with enzyme solutionsthat release the cells and the cells are treated with chelating agents or enzymes. • The freshly isolated cells are suspended in buffersolution. • At the time of experiment, the cells are separated, resuspended in buffer containing the drug under O2/CO2 and shakenwell. • After a specific period of time, the cells are separated by filtration, extracted and drug absorbed isdetermined. Siddhapura Pratik ( M.Pharm Pharmaceutics)

37. 6.TISSUETECHNIQUES a). Everted small intestinal sactechnique: • this method involves isolating a small segment of the intestine of a laboratory animal such as rat, inverting the intestine and filling the sac with a small volume of drug free buffersolution. • Both the segments are tied off and the sac is immersed in an ERLENMEYER FLASK containing a large volume of buffer solution that contains thedrug. • The flask and its contents arethenoxygenated and thewhole preparation is maintained at 37°C and shakenmildly. • At predetermined time intervals, the sac is removed and the concentration of drug in the serosal fluid is determined/assayed for drugcontent. Siddhapura Pratik ( M.Pharm Pharmaceutics)

38. Advantage -the epithelial cells of the mucosal surface are exposed directly to the oxygenated mucosalfluid. -Prolongs the viability and integrity of the preparation after removal from theanimal. -Convenience and accuracy with respect to druganalysis. Disadvantage - Difficulty in obtaining more than one sample per intestinal segment Siddhapura Pratik ( M.Pharm Pharmaceutics)

39. Fig. Everted sactechnique Siddhapura Pratik ( M.Pharm Pharmaceutics)

40. b)- EVERTED SACMODIFICATION • In this method, the test animal is fasted for a period of 20-24 hr and water isallowed. • The animal is killed and the entire small intestine is everted. Segments, 5-15 cm in length are cut from a specific region of the intestine. • The distal end of the segment is tied and the proximal end is attached to the cannula. The segment is suspended in a mucosal solution which contains thedrug. • A drug free buffer is then placed in the serosalcompartment. Siddhapura Pratik ( M.Pharm Pharmaceutics)

41. For determining the rate of drug transfer, the entire volume of serosal solution is removed from the sac at each time interval with the help of a syringe and replaced with fresh buffer solution. Fig. Everted sacmodification Siddhapura Pratik ( M.Pharm Pharmaceutics)

42. The amount of drug that permeates the intestinal mucosa is plotted against time to describe the absorption profile of drug at any specificpH. Advantage • A number of different solutions may be tested with a single segment of theintestine. • Simple andreproducible. • It distinguishes between active and passivediffusion. • It determines the region of small intestine where absorption is optimal, in the case of activetransport. Siddhapura Pratik ( M.Pharm Pharmaceutics)

43. Used to study the effect of pH, surface active agents, complexation and enzymatichydrolysis. Disadvantage - The intestinal preparation is removed from the animalas well as from its normal blood supply. Under these conditions, the permeability characteristics of the membrane are significantly altered. - The rate of transport of drug as determined from the everted sac technique, may be slower than in the intact animal. Siddhapura Pratik ( M.Pharm Pharmaceutics)

44. c). CIRCULATIONTECHNIQUES • In this method, small intestine may or may not beeverted. • This involves isolating either the entire small intestine of small lab animal or a segment and circulating oxygenated buffer containing the drug through thelumen. • Drug free buffer is circulated on the serosal side of the intestinal membrane andoxygenated. • Absorption rate from the lumen to the outer solution are determined by sampling both the fluid circulating through the lumen andoutside. Siddhapura Pratik ( M.Pharm Pharmaceutics)

45. Advantage • This method is applicable to kinetic studies of the factors affecting drugabsorption. • Both surfaces areoxygenated. • Eversion is notnecessary. Siddhapura Pratik ( M.Pharm Pharmaceutics)

46. d). EVERTED INTESTINAL RING ORSLICE TECHNIQUE • In this technique, the entire small intestine is isolated from the fasted experimental animal and washed with saline solution and dried by blotting with filterpaper. • The segment is tied at one end and by placing on glass rod it is carefully everted and cut into smallrings. • The everted intestinal rings are then incubated in drug containingbuffer maintained at 37c with constantoxygenation. • Under optimal conditions, rings remain viable for up to 2 hours and the transport of drug is stopped by rinsing the rings with ice cold buffer and dryingthem. Siddhapura Pratik ( M.Pharm Pharmaceutics)

47. At selected time interval, the tissue slices are assayed for drug content and expressed asmol/gm/time. Advantage • Simple andreproducible. • Kinetic studies can beperformed. • Each animal can act as its own control as many rings can be prepared from each segment of the intestineisolated. • Mechanism of drug absorption can be studied by changing the experimentalconditions. Disadvantage • Extreme care is needed to maintain to viability of the tissue throughout theexperiment. • tissue needs to be disrupted completely for the determination of drug contents, which complicates the assayprocedure. • polarity of the absorption cannot beassayed. Siddhapura Pratik ( M.Pharm Pharmaceutics)

48. 7. DIFFUSION CELLMETHOD • In this method, small segments of small intestine are mounted between two glass chambers filled with buffer at 37C. • Diffusion cell consist of two compartments:- • Donor compartment - which contains the drug solution and the lower end of which contains the synthetic or natural GI membrane that interfaces with the receptorcompartment. • Receptor compartment - which contain the buffersolution. Siddhapura Pratik ( M.Pharm Pharmaceutics)

49. Fig. Diffusion cell for studying drug uptake fromGIT Siddhapura Pratik ( M.Pharm Pharmaceutics)

50. 8. CELL CUTURETECHNIQUES • Cell culture is the complex process by which cells are grown under controlled conditions, generally outside their naturalenvironment. • In this technique, differentiated cells of the intestine, originating from CaCo2 cells ( cells of carcinoma of colon) are placed on synthetic polycarbonate membrane previously treated with an appropriate material such as collagen which on incubation aids reproduction of cells while not retarding drug permeation characteristics. • These models are based on the assumption that passage of drugs across the intestinal epithelium is the main barrier for drugs to reach thecirculation. Siddhapura Pratik ( M.Pharm Pharmaceutics)