Formulation and Evaluation of Timolol Maleate Gel Containing Stimuli Sensitive Polymers

Transcription

1 Formulation and Evaluation of Timolol Maleate Gel Containing Stimuli Sensitive Polymers N. Roshan* 1, M. Rahul 2 1 Shri Jagdishprasad Jhabarmal Tibrewala University, Dist-Jhunjhunu, Raj, India 2 Dr.Vedprakash Patil College of pharmacy, Aurangabad, MS, India ABSTRACT The present study was conducted on drug delivery to the ocular route. To achieve a bioavailability of the formulation is the main motto. Polymers with suitable rheological properties can facilitate the absorption of poorly absorbed drugs by increasing the contact time of the drug. This has been attributed to the rheological properties of the gel. The main objective of this work was to investigate the importance of the rheological and bioresponsive properties of a gel on the contact time that can be expected in vivo. This is exemplified by ocular route administration. The developed formulation was combination of temperature/ion/ph and light responsive polymers. The insitu gelling polymers like temperature sensitive pluronic, ph sensitive polymers- carbopols, chitosan, ion responsive polymers sodium alginate, light responsive polymers DMAA was found to be favorable rheological properties and invitro performance. The invitro studies were studied on different membranes to evaluate its release behavior and it was concluded that fabricated formulation was promising for ocular drug delivery. The potential properties of polymers were studied and measured by various analytical methods for their performance. Finally formulations were studied on blood samples to check its effect on RBCs. The formulation was subjected to accelerated condition to evaluate its stability in various environmental scenarios. Keywords - polymers, rheological, bioavailability, bioresponsive INTRODUCTION Rapid progress in the synthesis and utilization of functional polymers has been noted in the recent past. Interest in the field is being enhanced by the possibility of creating systems that combine the unique chemical properties of conventional active moieties and the characteristic physical properties arising from the high molecular weight system. A polymer is a chemical compound or mixture of compounds consisting of repeating structural units created through a process of polymerization. The response of a polymer can be defined in different ways depending on the restrictions on the mobility of the polymeric segments. Smart polymers which reversibly change their physical properties in response to small *Corresponding Author N. Roshan 82 P a g e

2 and controllable stimuli (change in temperature, ph, ion, light, etc.) to control recognition events by acting as environmental antennae and switches [1]. Polymer materials that respond to external stimuli such as temperature, ph, solvent quality, pressure, light etc. by changing their physical or chemical properties have become a topic of major interest in the last few decades [2]. For instance, the dimensional change of a polymeric solution can be higher than the dimensional change in a gel, because of relative restricted mobility within the network in the latter. Therefore, there can be limitations to a response. A response can be a size change, a change in secondary structure, a color change, a solubility change, or changes in the degree of intermolecular association [3]. Physical properties of polymeric materials can be modified by controlling various parameters. Chain conformation, configuration, color and solubility can be induced by external stimuli. Swelling/deswelling of hydrogels, shape memory of thin films, and self assembly of polymers in solution to produce aggregates with respect to the external stimuli are a few examples [3]. MATERIAL AND METHODS Pluronic, Chitosan, Carbopols, Sodium alginate, DMAA was supplied by signet and BASF chemicals. Sodium chloride, BKC, Dextrose were procured from local vendor. Timolol maleate was procured from royal pharmaceuticals, Mumbai. Methods: Simulated Tear Fluid Preparation [4, 5]: The simulating tear fluid (1000ml) was composed of NaCl 0.67g, NaHCO g, CaCl 2.2H 2 O 0.008g and deionized water to 100g. Preparation of 1N acetic acid: Solution of any molarity (x M) may be prepared by diluting 57ml (60g) of glacial acetic acid to 1000ml with purified water. Egg Membrane Preparation [6]: Make an aperture at one end of egg and yolk was removed completely. Add concentrated hydrochloric acid to egg shell. Wait until the bubbling stops and the foam disappears. The left over substance is eggshell. The following reaction mechanism occurs during reaction of egg shell with acid. Fabrication of Drug product: Fabrication of formulation was by cold method. Poloxamer was dissolved in Purified water and kept for hydration at C for overnight. Timolol maleate was dissolved in Poloxamer solution. Carbopol/Chitosan was soaked in water/acetic acid. Stirring was done to solubilize the system. Sodium alginate/dmaa was dissolved in purified water under stirring. Slowly addition of Carbopol/Chitosan solution in Poloxamer solution followed by addition of Sodium Alginate/DMAA solution under slow stirring. Final addition of viscosity enhancing agents, isotonic agent, preservatives for physical properties. Required volume of formulation was made with addition of Purified water. Fabricated formulation was finally sterilized and packed. Each ml of formulation 0.5% contains 5 mg of timolol (6.8 mg of timolol maleate) CaCO3 (s) + 2HCl (aq) _ CaCl2 (aq) + CO2 (g) + H2O (l). 83 P a g e

3 Absorbance (nm) Table 1: Composition for fabrication of drug product Batch Code Ingredients l ll lll llll lllll Timolol Maleate DMAA Poloxamer Poloxamer Chitosan Carbomers 971P Carbomers 974P Sodium Alginate Guar gum Hypromellose(3cps) BKC Purified water Sodium chloride Dextrose RESULTS AND DISCUSSION Standard plot of drug substance: An accurately weighted quantity of 10mg was dissolved in100ml of simulated tear fluid to generate a primary stock solution having a concentration of 0.1mg/ml or 100µg/ml ml aliquots of the primary solution were further diluted to Table 2: Tabular representation of Concentration with respect to absorbance 10ml to produce standard solutions having concentration range of 5-40µg/ml. The absorbance of the solution was measured at 294 nm using UV spectrophotometer against simulated tear fluid as a blank. The plot of absorbance Vs concentration µg/ml was plotted and data was subjected to linear regression analysis. S.N. Conc. (µg/ml) Absorbance Standardization curve for Timolol Maleate Concentration (µg/ml) Graph 1: Graphical presentation for standardization curve 84 P a g e

4 Measuring Physic-chemical properties: The physic-chemical properties of the prepared formulation were studied with respect to drug content, clarity, appearance and ph of the formulation. The clarity is an important factor in ophthalmic formulation which if avoided may cause blurred vision after administration. The fabricated formulation were found to be satisfactory, and within acceptable limits. Gelation temperature: Fabricated formulation was kept in contact with condition maintained with 37 0 C and gelation of temperature responsive formulation was evaluated. Gel Persistent Capacity: The integrity of gel should be preserved to facilitate sustained release action of drug without dissolving or eroding. The glass tube containing simulated tear fluid and maintaining physiological condition like temperature, ph, ion and light. A drop of formulation was added in to glass tube and integrity of gel was evaluated for 8-10 hrs. Viscosity: The formulation exhibits pseudo plastic rheology. Viscosity of the formulation depends upon polymeric concentration present in it. Generally a viscosity value in the range of 15-50cps significantly improves the contact time in the eye [7]. The administration of ophthalmic preparation should influence as little as possible the pseudo plastic character of the precorneal film. Since the ocular shear rate is very high ranging from 0.03sec -1 during interblinking periods to sec -1 during blinking [8]. Osmolarity: When formulated for topical administration to the eye the drug delivery vehicles of the present invention have an osmolarity of about 350 mosm or less. Compositions having an osmolarity greater than about 350 mosm are hypertonic and can be irrtiating when topically administered to the eye [9]. Table 3: Evaluation of physic-chemical properties of fabricated formulation Batch code Gelation temperature ( 0 C) ph Appearance Clarity Content uniformity (%) GPC (hrs) l Free flowing liquid Clear ll Free flowing liquid Clear lll Free flowing liquid Clear llll Free flowing liquid Clear lllll Free flowing liquid Clear P a g e

5 % Drug release Viscosity viscosity graph for formulation Angular velocity Graph 2: Drug permeation behaviour on cornea of goat Drug permeation study on Goat eye cornea: The drug release behaviour can be determining percutaneous absorption through human skin. But due to heavy potency of drug in vivo studies in human is very critical. Beside this evaluation was carried out on eye cornea of goat Drug permeation study through eye cornea of goat Time (mins.) Graph 3: Drug permeation behaviour on cornea of goat Preservative efficacy testing: Organisms used for study are E.coli, P. Aeruginosa, S. Aureus, C. Albicans and A. Niger. Dilution media was prepared by weighing soya lecithin (0.05%), NaCl (0.9%), Tween (0.02%) and Pepton (0.01%). The media was poured into predried and sterilized test tubes and volume 9ml was added and then plugged with cotton and kept for auto claving at C at 15psi.Soya lecithin act as anti preservative which helps in growth of organism tween as a surfactant helps in reducing the surface tension between organism and diluents, NaCl as tonicity modifier and peptone too [10]. Osmolarity: Osmotic pressure plays important role in all biological process that involves diffusion routes to transfer fluid through 86 P a g e

6 membrane. Osmosis occurs when solvent but not solute molecule cross a semi permeable membrane from regions of lower to higher concentration to produce equilibrium. The knowledge of osmotic pressure is important for practitioners in determining whether a parental solution is hypo-osmotic, isotonic and hyper osmotic. A quantitative measure of osmotic pressure facilitates the dilution required to render a solution iso-osmotic relative to whole blood. Osmolarity of a solution is a theoretical equation expressed in osmoles per liter of a solution and is widely used in clinical practices because it expresses osmoles as a function of volume. Osmolarity cannot be measured but it is calculated theoretically from the experimental measured value of Osmolarity. Osmolarity = v i c i Where, v i and c i are molar concentration of the i th solute in addition. The limit for Osmolarity of blood ranges from mosmol/kg. The osmolarity of fabricated timolol maleate gel forming eye drop was computed and found to be 295 mosmol/kg. Effect of Formulation on RBC and to determine the count: Red Blood Corpuscle (RBC) is a circular, biconcave, non-nucleated disc. [11] Diameter: micron. Thickness: periphery: micron, at the centre: micron. Surface area: 140 micron square. Volume: micron cube of fl (86 micron cube). Normal value: Male: 5 to 6.5 millions/mm 3, Female: 3.5 to 5 millions/mm 3. RBC does not have the nucleus and hence they evaluating parameter for determining formulation effect on blood cells. Procedure: Focus Neubauer s chamber with cover slip under high power observes the central square demarcated by triple lines. With aseptic precaution take a bold prick. Fill RBC pipette up to the mark 0.5. Suck RBC diluting fluid up to mark. Mix thoroughly by rolling the pipette between two palms. Discard the first two drops. Charge Neubauer s chamber. The central square of Neubauer s chamber is divided into 25 small squares. Out of this 25 small squares, count the RBC s in central most and four corner squares, follow the rule of L while RBC counting [12]. The blood drop was placed on glass slide and a drop of formulation was placed over it and mixed with help of another glass slide. The Blood drop was observed under high resolution microscope to check any discrepancy. The RBC count was also determined. The blood drop evaluation under microscope was found to be normal and RBC counts where within the limit range (4.1millions/mm 3 ). CONCLUSION Phase transition systems are those which upon instillation into eye, shift from liquid to solid phase. In case of pluronic F127, the viscosity of the solution increases gradually in contact with eye temperature. Pluronic F127 based controlled release action in ocular delivery system for Timolol Maleate. Carbopols 940 forms gel when is native ph changes to ph of tear fluid. Timolol Maleate used in the 87 P a g e

7 treatment of glaucoma was successfully formulated as ph-temperature-ion-light triggered in situ forming eye drops. The developed formulation body was free flowing liquid having ph and undergoes gelation upon rise in ph, at body temperature and in presence of Ca ++ ions. The gel persistent consistency and its release action were studied for 9hrs. Thus in situ gelling system will show good patient acceptance due to its ease in instillation into eye and decreases of application intervals. The long residence time of the gel formed, along with its ability to release drug in a sustained manner will assist in enhancing bioavailability of drug. The rapid corneal elimination of drugs given in eye drops is mainly due tear fluid or conjunctional absorption. Topically applied drugs are immediately diluted in tear fluid secreted from eyes and thus spill or drained through nasolachrymal duct. Thus a right quantity of drug is not available for therapeutic action and so many ophthalmic drugs are applied in high dose which may cause ocular irritation and systemic side effects. This problem has overcome by using insitu gel forming systems. The formulations fabricated using such polymers that exhibits reversible phase transitions and pseudo plastic behavior which are suitable for administration which upon exposure to physiological conditions will shift to gel phase thus enhance bioavailability. Thus formulation containing poloxamer, chitosan, sodium alginate and DMAA showed effective results and use as delivery system with better ocular bioavailability. REFERENCE 1. Patrick Stayton, Allan Hoffman, Noah Malmstadt, Samarth Kulkarni, Stimuli Responsive Polymeric Devices, Patent no.: US B2. 2. Darinka Christova, Rumiana Velichkova, Wouter Loos, Eric J. Goethals, Filip Du Prez (2003), New thermo-responsive polymer materials based on poly(2-ethyl-2- oxazoline) segments, Polymer, Erandimala Udamini Kulawardana (2010), Stimuli-Responsive Polymers - A Dissertation. 4. Wen-Di Ma, Hui Xu, Chao Wang, Shu-Fang Nie, Wei- San Pan (2008), Pluronic F127-g-poly (acrylic acid) copolymers as in situ gelling vehicle for ophthalmic delivery system, International Journal Of Pharmaceutics, 350, Rozier A, Mazuel C, Grore T, plazonnet B (1989), Gelrite: A novel ion-activated, in situ gelling polymer for ophthalmic vehicles Effect on bioavailability of timolol, International journal of pharmaceutics, 57, Lechtanski, V. L. Calcium Carbonate (2000), Content of Eggshells Inquiry-Based Experiments in Chemistry, Oxford, Sindhu Abraham, Sharon Furtado, Bharath S, Basavraj BV (2009), Sustained ophthalmic delivery of ofloxacin from an ion activated in situ gelling system, Pakistan 88 P a g e

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