FORMULATION AND STABILITY TESTING OF EYE DROP PREPARATIONS CONTAINING PHENYLEPHRINE HYDROCHLORIDE CHINEDUM OLUCHUKWU OKAFOR FORMULATION AND STABILITY TESTING OF EYE DROP PREPARATIONS CONTAINING PHENYLEPHRINE HYDROCHLORIDE CHINEDUM OLUCHUKWU OKAFOR Submitted in fulfillment of the requirements for the degree of MAGISTER SCIENTIAE in the FACULTY OF HEALTH SCIENCES at the NELSON MANDELA METROPOLITAN UNIVERSITY DECEMBER 2012 SUPERVISOR: Mrs. M. Keele CO-SUPERVISORS: Dr M. Worthington, Prof. G. Kilian ii DECLARATION I, Chinedum Oluchukwu Okafor, 205010351, hereby declare that the dissertation for Magister Scientiae is my own work and that it has not previously been submitted for assessment or completion of any postgraduate qualifcaton to another University or for another qualification. Chinedum Oluchukwu Okafor iii ACKNOWLEDGEMENTS I wish to thank the following people and institutions for their assistance during the compiling of this dissertation: My exceptional families Okafor and Makamure for their steadfast support and love; Dr. M Worthington, as without sponsorship and guidance there could be no research; My supervisors, Mrs. M. Keele, and Prof. G. Kilian for guidance and support; Prof. Milne, for his unwavering support, no words in the dictionary can describe his help; Michael (Aspen), Jean, Charne and Arista (NMMU) for her input, support and exceptional skills at sourcing materials for me; Aspen Pharmacare, for financial assistance and the use of equipment and materials needed to perform my experiments; All my friends all around the world, every moment with you was a blessing. The Pharmacy, Biochemistry and Microbiology and Chemistry Departments of the Nelson Mandela Metropolitan University for the use of laboratory facilities and technical assistance; Above all, God Almighty, only through His Grace can I achieve all things. iv SUMMARY Phenylephrine hydrochloride is a potent adrenergic agent and β-receptor sympathomimetic drug, used in its optically active form (Pandey et al., 2003; Pandey et al., 2006). As an α1-adrenergic receptor agonist, phenylephrine hydrochloride is used ocularly as a decongestant for uveitis and as an agent to dilate the pupil (Lang, 1995). High intraocular doses have been reported to cause tachycardia, hypertension, and headache. These side effects are caused by large amounts of the drop draining into the nasal cavity. Eye drops that contain phenylephrine hydrochloride have proven to have low intra-ocular bioavailability because of a short contact time with the eyes which reduces the amount of drug reaching the site of action. Formulations of phenylephrine hydrochloride eye drops have varying shelf- lives of approximately two to four years. The aim of this study was to formulate and manufacture an eye drop product containing phenylephrine hydrochloride. Important characteristics that were targeted were increased ocular absorption by increasing the viscosity of the product and reduced degradation of phenylephrine hydrochloride. A variety of phenylephrine hydrochloride formulations were manufactured on a laboratory scale using hydroxypropyl methylcellulose (HPMC), glycerol, and sodium carboxy methylcellulose as viscosity modifying agents (VMA). The concentration of phenylephrine hydrochloride was ten percent. Ten millimeters of each formulation was made in triplicate. The quantity in each was evaluated using a previously validated high performance (pressure) liquid chromatography method. Physicochemical properties including pH and colour were also evaluated. Stability was assessed using real time and accelerated stability conditions in accordance with the International Conference on Harmonization (ICH) guidelines. Formulations containing hydroxypropyl methylcellulose (HPMC) as the viscosity modifying agents proved to be stable under all storage conditions when compared with formulations containing other viscosity modifying agents (VMA). However, sodium citrate dihydrate; sodium metabisulphite and EDTA also stabilized the formulations to a certain extent. v Changes in the appearance and colour of products containing glycerol under accelerated storage conditions were observed. The sodium carboxy methylcellulose (SCMC) containing formulation was found to be physically and chemically stable in two conditions, namely 30 °C/65%RH and 25 °C/60%RH. The formulations containing hydroxypropyl methylcellulose along with an antioxidant showed to be most stable as it remained aesthetically pleasing did not change colour and did not have a reduction in phenylephrine hydrochloride concentrations. This meant that phenylephrine hydrochloride did not degrade while the viscosity modifying agents remained stable. Rheological tests showed differences in the viscosities of the formulations as glycerol had increased in viscosity over time while HMPC and SCMC displayed relative similarities. The formulations were compared to a marketed eye drop containing polyvinyl alcohol as a VMA. After rheological analysis the formulation containing HPMC displayed better viscosity than the product with polyvinyl alcohol. The preservatives in the formulations were active against the microbial organisms use to challenged them. Key words: Phenylephrine hydrochloride, glycerol, hydroxypropyl methylcellulose, preservatives, storage conditions, viscosity. vi TABLE OF CONTENTS DECLARATION ...................................................................................................................... iii ACKNOWLEDGEMENTS ....................................................................................................... iv SUMMARY ............................................................................................................................... v TABLE OF CONTENTS ......................................................................................................... vii LIST OF ABBREVIATIONS ..................................................................................................... x LIST OF FIGURES ............................................................................................................... xiv LIST OF TABLES ............................................................................................................... xxviii 1. INTRODUCTION ............................................................................................................. 1 1.1 Background and motivation ...................................................................................... 1 1.2 Aim and objectives ................................................................................................... 2 1.3 Plan of work .............................................................................................................. 3 2. LITERATURE REVIEW ................................................................................................... 4 2.1 Anatomy and physiology of the eye ......................................................................... 4 2.2 Pathophysiology of the eye ......................................................................................... 10 2.3 Phenylephrine hydrochloride and its ocular uses ........................................................ 14 2.3.1 Phenylephrine hydrochloride .................................................................................... 14 2.3.2 Pharmacological actions and uses ........................................................................... 15 2.3.3 Mechanism of action ................................................................................................ 15 2.3.4 Pharmacokinetics ..................................................................................................... 16 2.3.5 Adverse effects ......................................................................................................... 16 2.3.6 Drug interactions ...................................................................................................... 17 2.3.7 Bioavailability ............................................................................................................ 17 2.3.7.1 Reasons for poor ocular bioavailability .................................................................. 18 2.3.7.2 Strategies for improving drug availability in ocular adminstration ......................... 19 2.3.7.2.1 Increasing ocular residence time ........................................................................ 19 2.3.7.2.2 Increasing ocular absorption .............................................................................. 19 2.3.7.2.3 Altering drug structure ........................................................................................ 20 2.3.8 Polymorphism and pseudomorphism of phenylephrine hydrochloride ..................... 21 2.4 Ophthalmic formulations .............................................................................................. 21 2.4.1 Eye drops as an ophthalmic dosage form ................................................................ 22 2.4.2 Eye drop formulation characteristics ........................................................................ 24 2.4.2.1 Clarity .................................................................................................................... 24 2.4.2.2 Stability, pH and buffer systems ............................................................................ 25 2.4.2.3 Tonicity .................................................................................................................. 26 vii 2.4.2.4 Viscosity ...............................................................................................................