The Effect of Solid-State Forms on the Topical Delivery of Roxithromycin
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The effect of solid-state forms on the topical delivery of roxithromycin C Csongradi 22157352 Dissertation submitted in fulfilment of the requirements for the degree Magister Scientiae in Pharmaceutics at the Potchefstroom Campus of the North-West University Supervisor: Dr Minja Gerber Co-Supervisor: Prof Jeanetta Du Plessis Assistant supervisor: Dr Marique Aucamp October 2015 This dissertation is presented in the so-called article format, which includes sub-chapters, three articles for publication in pharmaceutical journals and annexures containing experimental results and discussion. The three articles for publication each have specific author guidelines for publishing in Annexures E, F and G. Success is no accident. It is hard work, perseverance, learning, studying, sacrifice and most of all, love for what you are doing – Pele Acknowledgements I am very blessed to have had my Almighty God as my number one support throughout my two years of completing this dissertation. I thank Him for giving me strength when I was faced with difficulties and for placing wonderful people in my life that supported me throughout this time. I would like to sincerely thank the following people for their support and on-going contribution to this study: First and foremost, my fiancé, Mario, thank you for loving me and being there for me every step of the way, for your visits, your help, your motivation and for doing the little things that made the bad days so much better. My parents, none of this would have been possible without your unconditional love and constant support. Dad, thank you for your all your advice and mom, thank you for all the trips you made to Potchefstroom whenever I needed your help and for making me feel like I was never alone in all of this. My supervisor, Dr Minja Gerber, thank you for all your assistance, guidance and expertise in these two years. I appreciate that you were always so willing to help every time I knocked on your door and thank you for always being there for me. My co-supervisor, Prof Jeanetta Du Plessis, thank you for all the input and advice you gave me when I was faced with difficulties in this study. Dr Marique Aucamp, my assistant supervisor, I cannot thank you enough for being by my side in the labs and going out of your way to help me with problems that were not even in your field of study. There were times I felt like I was failing but I am so thankful that you were always there to laugh about the difficulties and lift my spirits. The passion you have for research is very inspiring. Mrs Alicia Brümmer, thank you for all your hands on help in the lab during my diffusion studies and for always doing your best to help where ever you could. I appreciate all you have done for me. Prof Jan Du Preez, thank you for your help and contributions you offered whenever I asked for advice. Prof Lissinda Du Plessis, I appreciate your help with the entrapment efficiencies of the vesicles and for being so helpful by giving me so much information for this study. i Dr Anine Jordaan, thank you for all the help with the TEM microscope. Prof Faans Steyn, I am so thankful for your contribution to the statistical analysis part of this study. Mr Neil Barnard, I am grateful for all your willingness to always help me in the laboratories. Ms Hester De Beer, thank you for all your administrative work. To my colleagues and friends, thank you for making this journey so enjoyable. Angelique, Kim, Chantelle and Sarah, thank you for taking my mind off all the stress of the work and for all the memories in these two years. Especially thank you to Jani van der Westhuizen for always going out of your way to give me advice, help and guidance during this study and for giving me footsteps to follow in. A big thank you to the National Research Foundation (NRF) for the necessary funds needed for making this study possible. The financial assistance of the NRF towards this research is hereby acknowledged. Opinions expressed and conclusions arrived at, are those of the author and are not necessarily to be attributed to the NRF. ii Abstract The skin is a very accessible and convenient route of administration for topical and systemic drugs (Williams, 2003:1). The only problem most formulators face is overcoming the barrier function of the stratum corneum, which has proved to be quite a challenge (Varun et al., 2012:632). This being said, the topical/transdermal route still holds many advantages over other routes of administration, with the most obvious being no first-pass effect from the liver and being a non-invasive, painless route of administration (Washington et al., 2001:187). The skin itself is affected by many diseases and one of the most common, from which a large number of the population suffers, is acne (Bershad, 2001:279). Acne vulgaris is a chronic inflammatory disease which affects the pilosebaceous units found in the dermis layer of the skin and the micro-organism which accumulates in these sebaceous glands and causes the inflammation, is known as Propionibacterium acnes. Topical antibiotics have a direct affect against P. acnes found in the sebum glands and in this way reduce the acne inflammation (Williams et al., 2012:361, 364). The antibiotics used today for the treatment of acne have been reported to be up to 60% resistant to the acne causing bacteria (P. acnes) (Scheinfeld et al., 2003:43). In the recent past, trials have been conducted on newer antibiotics for acne treatment, one in particular is roxithromycin (Oschsendorf, 2006:830). Roxithromycin is a macrolide antibiotic which has a bacteriostatic effect on P. acnes which accumulates in the dermis, but its poor solubility has been a major drawback for topical drug formulation (Gollnick, 2003:1585; Medsafe, 2014). For optimal skin penetration, a compound must preferably have an aqueous solubility above 1 mg/ml (Williams, 2003:37) and roxithromycin was reported to have a solubility of only 0.0335 mg/ml at 25 °C, which is below the optimal solubility for topical penetration (Aucamp et al., 2013:26; Williams, 2003:37). It has previously been proved that by using amorphous forms of a compound, along with its changed crystal lattice, can result in improved drug properties including increased solubility (Biradar et al., 2006:22; Purohit & Venugopalan, 2009:883). Patents from Liebenberg et al. (2013) and Liebenberg & Aucamp (2013) proved the glassy amorphous form of roxithromycin and the chloroform desolvated amorphous form had improved solubilities in comparison to the crystalline monohydrate form. Another area of research that has shown much growth is that of vesicle carrier systems, which have the ability to improve therapeutic activity of drugs by increasing the topical delivery of especially poorly soluble drugs such as roxithromycin (Bansal et al., 2012:704). Niosomes are used as an alternative to liposomes in current years as it overcomes the chemical instability, high cost and lack of purity of phospholipids (Jadon et al., 2009:1186). Niosomes are liposomes which are prepared using non-ionic surfactants instead of phospholipids and iii ufosomes are liposomes made from fatty acids (Bansal et al., 2012:710; Williams, 2003:128- 129). Provesicular systems, such as proniosomes and pro-ufosomes, are prepared in order to overcome the stability problems that vesicular carriers face (Bansal et al., 2012:706, 709). The aim of this study was to determine if the two amorphous forms of roxithromycin, namely the glassy form and the chloroform desolvate, coupled with better solubility would have better topical diffusion. These three solid-state forms were each encapsulated into four chosen vesicle systems namely, niosomes, proniosomes, ufosomes and pro-ufosomes and the delivery of the two amorphous forms were compared to that of the crystalline monohydrate form to determine if an increase in topical delivery took place. The target area for the active pharmaceutical ingredient (API) was the dermis, as this is the area where P. acnes accumulates (Gollnick, 2003:1585). The optimisation and characterisation of amorphous forms entrapped in vesicles proved that all carrier systems were well formed and had optimal properties for topical delivery. An accurate and reliable high performance liquid chromatography (HPLC) method of analysis was developed and validated for the analysis of roxithromycin samples during experiments. The release studies showed that the API was successfully released from all carrier systems, with niosomes and proniosomes having superior release over the ufosomes and pro-ufosomes. The reason for this was that the API had higher affinity (and therefore less release) for the ingredients used to make ufosomes and pro-ufosomes (Agarwal et al., 2001:49; Dayan, 2005:74). The topical diffusion studies showed that there was no API concentration detected in the stratum corneum, which meant the API successfully penetrated the barrier. There was practically no API found in the receptor phase of the Franz cells which indicated that there was no systemic absorption and that the vesicle systems aided in drug targeting. An API concentration was found in the epidermis-dermis of all vesicle systems, which proved the intended target area for roxithromycin was successfully reached. The vesicle systems which assisted in the delivery of roxithromycin and its amorphous forms, from highest to lowest diffused concentration, were niosomes, ufosomes, proniosomes and pro-ufosomes. The total concentration was more dependent on the carrier type than the solid-state form, as there was no obvious leading roxithromycin form. Nevertheless, when the solid-state forms were grouped together, regardless of what carrier systems they were delivered in, the amorphous forms had higher epidermis-dermis concentrations than the roxithromycin monohydrate.