In Situ gels and nanocomposite systems for intranasal delivery of dimenhydrinate

Abstract

There has been a great focus on intranasal drug delivery as an alternative route for both oral and systemic routes besides its brain targeting. The high vasculature of the nasal mucosa and the direct connection to the brain through the olfactory bulb in the nose offer superior advantages in terms of rapid action, non-invasiveness and brain targeting and thus improve the patient compliance. Based on all these facts, this study focused on the development of an efficacious intranasal formulation of the antiemetic drug dimenhydrinate. DMH is an ethanolamine antihistamine used as an OTC drug for the prevention and treatment of nausea, vomiting, dizziness, and vertigo associated with motion sickness. Moreover, it is used for the prevention of postoperative and drug induced vomiting. The main goal of this work was to bypass the first pass metabolism experienced by the oral delivery of the drug and to enhance its brain bioavailability, in addition to achieving rapid drug delivery in emergency vomiting control. For achieving these goals two approaches were attempted; the first was to formulate an in situ mucoadhesive nasal formulation thus increasing the residence time and the contact with the nasal mucosa for better drug absorption, while the second approach was to entrap the drug in penetration enhancer containing vesicles (PEVs) which are vesicular systems consisting of one or more concentric spheres of lipid with a penetration enhancer which are then incorporated in the in situ gelling system creating a composite system.

The work in this thesis was divided into three chapters Chapter I: Preparation and characterization of dimenhydrinate nasal mucoadhesive in situ gelling systems This chapter dealt with the formulation and characterization of dimenhydrinate thermosensitive in situ gels. Using the cold method formulations containing different concentrations of the thermosensitive polymers P407 and P188 were prepared and the mucoadhesive sodium hyaluronate was then incorporated. The formulations were characterized through the following studies; gelation temperature, viscosity, in vitro drug release and mucoadhesion. Stability of the selected dimenhydrinate in situ forming gel stored in fridge was conducted as well. The results of this work revealed the following: • In situ forming gels of dimenhydrinate were successfully prepared using poloxamer polymer. • It was revealed that the use of poloxomer 407 (P407) didn't give gel in the physiological temperature range, and that a combination of P407 and P188 should be used. • Chitosan was not a suitable mucoadhesive agent for the prepared in situ gelling systems of dimenhydrinate, and only hyaluronic acid was successfully incorporated. • The physiological gelation temperature range after the addition of HA, was only achieved at P407/ P188 ratios of (19/12) and (20/11) respectively. • The addition of the mucoadhesive HA by a concentration of 0.5% had a significant impact on gelation temperature of in situ gelling systems while increasing the concentration to 1% showed insignificant difference on the former (containing 0.5% HA). • Increasing the temperature from 25 ˚C to 37 ˚C caused the viscosity of the in situ gelling systems to be significantly increased due to the gel formation, proving the thermosensitivity of the polymer. • The variation in poloxomer composition caused non-significant increase in viscosity of in situ gelling systems, while the addition of the mucoadhesive agent HA generally increased the viscosity of the formulations in a significant way. • The poloxomer based in situ gelling systems prepared provided a sustained release of dimenhydrinate over 6 hours, with a cumulative percentage of drug released reaching 66.28% after 6 hours. • Generally, the addition of HA led to significant increase in the mucoadhesive force of the formulations. • The in situ forming gel formula (F27) composed of 19% P407, 12% P188 and 1% HA as mucoadhesive agent was selected for the creation of nanocomposite in situ forming gelling system in the next chapter as it showed gelation at the physiological temperature with acceptable viscosity and mucoadhesion.

Chapter II: Preparation and characterization of dimenhydrinate nanocomposite in situ forming gels. This chapter dealt with the formulation, and characterization of dimenhydrinate vesicles (Penetration enhancer containing vesicles). PEVs were prepared by the reversed phase evaporation technique (REV) using different amounts of phospholipid in the presence of the penertration enhancers labrasol and transcutol. The prepared PEVs were characterized through the following studies; EE%, particle size analysis, zeta potential and PDI. Stability of the dimenhydrinate PEVs stored at fridge for three months was conducted as well. The PEVs with optimum dimenhydrinate entrapment efficiency and acceptable particle size and PDI in the nano range were selected for further incorporation in a thermosensitive in situ forming gelling system previously optimized in chapter I while trying other poloxomer ratios. The prepared nanocomposite in situ forming gels were then evaluated for their gelation temperature, viscosity, in vitro release, mucoadhesion and the stability was conducted upon three months storage period in terms of measuring the gelation temperature.

The results of this work revealed the following: • The dimenhydrinate loaded PEVs were successfully prepared by the reversed phase evaporation technique (REV) using labrasol and transcutol as penetration enhancers. • The EE% for dimenhydrinate in PEVs ranged from 78.915 ± 3.46 % to 95.35 ± 0.15%. • The EE% of DMH was not affected by the phospholipid amount; where by scaling up the amount of phospholipid there was an insignificant variation in EE% without certain pattern. • The particle size of the formed PEVs ranged from 59.46 ± 1.6 nm to 266.5 ± 20.5 nm. It was clear that by increasing the amount of phospholipids the particle size significantly increased. • Increasing the amount of the penetration enhancers (PEs) labrasol and transcutol resulted in a significant decrease in the particle size. • The polydispersity index (PDI) values of the prepared PEVs were in the range of 0.251 ± 0.07 to 0.75 ± 0.05. • Storage for three months resulted in a significant increase in particle size of PEVs of formulae (K1-K3) and an insignificant increase in particle size of PEVs of formulae (K4-K6). • The zeta potential of the PEVs of all the PEVs formulae has shown an insignificant change upon storage. • TEM showed the outline and the core of spherical vesicles. • Incorporating the selected DMH loaded PEVs in the selected in situ gel with the combination of P407 and P188 at a ratio of 19% and 12% respectively increased the gelation temperature dramatically above the physiological required temperatures. • The DMH loaded nanocomposite in situ gelling formula (K14) with %w/v (P407/P188) ratio of (18.5/11.5) and (K15) with %w/v (P407/P188) ratio of (18.75/11.25) exhibited gelation temperature in the physiological range (32.83 ± 1.04 ˚C and 35.67 ± 0.29 ˚C respectively). • The viscosity of the DMH loaded PEVs (K4) was not affected by temperature increase from 25 ˚C to 37 ˚C while the nanocomposite in situ gelling formula showed significant viscosity increase. • The formulae showed a satisfactory sustained drug release rates within 6 hours. The percentage of drug release from the PEVs formula (K4) ranged from 4.94 ± 0.44% after the first 15 minutes to 46.11 ± 1.71% at the end of the 6 hours. • The DMH loaded nanocomposite in situ gelling formula (K15) containing poloxamer and the mucoadhesive HA after the first 15 minutes showed percentage of drug release of 2.66 ± 1.17% and after the 6 hours the percentage of drug release was 24.99 ± 1.89%. • The DMH loaded nanocomposite in situ gelling formula (K15) showed higher mucoadhesiveness than the DMH loaded PEVs (K4) owing to the presence of poloxamers and hyaluronic acid in the former. • The gelation temperature of the stored DMH loaded nanocomposite in situ gel (K15) was 34 ± 0.5 ˚C, which lied in the physiological range. • The DMH loaded PEVs (K4) composed of 600 mg phospholipids and penetration enhancers (labrasol and transcutol) each 1 ml in addition to 200 mg DMH and 0.5 ml PEG 400 as a solubilizer was selected as a representative to a drug loaded PEVs for further conduction of in vivo experiments in the next chapter. • The DMH loaded nanocomposite in situ gel (K15) composed of 600 mg phospholipids and penetration enhancers labrasol and transcutol each 1 ml in addition to 200 mg DMH and 0.5 ml PEG 400 as a solubilizer added to them (P407:P188) at ratio of (18.75:11.25) % w/v and 1% HA as a mucoadhesive, it was selected as a representative to DMH nanocomposite in situ gelling system for conduction of in vivo study in the next chapter Chapter III: Pharmacodynamic Study on the selected intranasal in situ gelling formulae of dimenhydrinate This chapter involved the examination of the in vivo therapeutic effectiveness of the selected formulae prepared in chapters I and II. This was done by evaluating the ability of the selected formulae to prevent the cisplatin induced pica effect in rats which was used as an animal model analogue to motion sickness. Cisplatin as a pica inducing agent increases the kaolin intake, decreases the food and water intake and decreases the gastric emptying, resulting in an increase in the stomach content weight. The food, water and kaolin intake were assessed before and after cisplatin injection, the selected formulae were given before the cisplatin in order to test the efficacy of the formulae in preventing pica effect. After that the rats were killed by decapitation, and the gastric content for each rat was weighed. The work in this chapter included the following: 1. The three chosen formulae from chapters I and II to be studied for their intranasal antiemetic response in cisplatin induced pica models in rats were prepared. 2. Six groups of rats were used, each group included 8 rats, and each animal was placed in an individual cage for a three days habituation period prior to the start of the experiment. Group I acted as normal control, while group II rats acted as cisplatin control as they were subjected to pica induction with no prophylactic formula. 3. A thick paste of kaolin (China clay) was prepared by mixing kaolin with 1% gum Arabic. 4. Before the cisplatin intraperitonial injection (i.p.), three groups of rats were given the dimenhydrinate formulae intranasally; a formula for each group and a fourth group was orally given the marketed Dramenex®. 5. The food, water and kaolin intake of the six groups were assessed for three days before induction. The 24 hours post induction (cisplatin intraperitoneal injection) food, water and kaolin intake were also assessed in order to test the efficacy of the formulae in preventing pica effect. 6. After 24 hours of observation and assessment the rats were killed by decapitation, and gastric content was weighed. 7. Autopsy samples were taken from the nose of scarified rats after volume of 50 µl containing 1 mg dimenhydrinate of the selected final two formulae of chapters I and II were administrated in each nostril of male Wistar rats weighing 130-150 g by 24 hours for histopathological study. The results of this work revealed the following: