Non-invasive drug delivery to the posterior segment of the eye: Development of formulation strategies and evaluation of ocular distribution and pharmacological activity

Diseases of the posterior segment of the eye such as diabetic retinopathy, age related macular degeneration and glaucoma are the leading causes for blindness throughout the world. Topical eye drops is the most convenient formulation for daily application. The human eye, however, presents major physiological and dynamic barriers for the topically administered drug/molecule from reaching the retina. Similarly, the blood-retinal and blood-aqueous barriers restricts passage of drug from systemic circulation into the eye. Although intravitreal injections are the gold standards for the treatment of posterior segment ocular diseases, they are associated with pain, inflammation, endopthalmitis and infection. So there is a necessity to develop novel noninvasive drug delivery strategies to treat the posterior segment ocular diseases. In the present study, we have used melt cast technology to develop a polymeric matrix film system to deliver Hesperetin (HT), a bioflavanoid, to the posterior segment of the eye. The film is 4 mm x 2 mm in dimension and 0.2 to 0.4 mm in thickness. When the HT-film was tested in vivo in anesthetized rabbit model, HT levels were maintained above the neuroprotective and antiinflammatory IC50 levels for upto 6 h. We also prepared HT loaded (0.1% w/v) solid lipid nanoparticles (SLN’s) using a combination of 85% glyceryl monostereate and 15% compritol ATO 888. The particle size, zeta potential and entrapment efficiency of the HT-SLN’s was 225 nm, -21 mV and 85% respectively. Although the dose administered in the animal study was approximately 16-fold lower than the HT-Film, SLN’s provided very good HT levels in the anterior segment of the eye. These formulations were tested in the conscious animal model to determine the effect of active lymphatic and tear drainage. Significant elimination of HT was observed in the aqueous humor due to the turnover rate (1.0% to 1.5% of the anterior chamber volume per minute). But the film formulation was able to maintain 2.3 µg of HT/gm of tissue in the retina choroid and 80 ng of HT/gm of vitreous humor upto 3 h. SLN’s were able to deliver 1.9 µg of HT/gm of iris ciliary bodies, but HT levels were below detection limit in the posterior segment of the eye. Thus, polymeric matrix films prove to be a safe and effective platform for the delivery of drugs/drug candidates to the posterior segment of the eye. Glaucoma is the second leading cause for blindness worldwide. Rise in intraocular pressure (IOP) has been identified as an important risk factor in the pathogenesis of the disease. Δ9-Tetrahydrocannabinol (THC), an active ingredient of the plant cannabis sativa, and an agonist of the cannabinoid receptors, CB1 and CB2, could potentially be such a dual acting anti-glaucoma agent. Delivering therapeutic levels of THC into the inner ocular layers is very challenging due to the extremely lipophilic characteristics of THC. A synthetic amino acid dicarboxylic acid prodrug of THC, Δ9-Tetrahydrocannabinol valine hemisuccinate (THC-Val-HS) was developed. Micellar and nanoemulsion formulations of THC-Val-HS and THC were prepared. These formulations were evaluated for IOP reduction in an alpha chymotrypsin induced rabbit glaucoma model. With the 0.5%w/v THC emulsion formulation drop in IOP was observed at 30 min, but was very minimal and short acting (60 min). With an increase in dose (0.8% w/v THC) a similar effect was observed with a slight increase in the duration of activity (90 min). With THC-Val-HS (0.6% w/v THC equivalent), drop in IOP was observed at 30 min, but the maximum drop was observed at 90 min, lasting upto 3 h (90% of the baseline). The more gradual drop in IOP can be attributed to the fact that THC-Val-HS has to be enzymatically converted into THC to show activity. Receptor binding studies revealed that THC-Val-HS has 21.8 and 38 folds less affinity towards CB1 and CB2 receptors, respectively, than THC. Thus, the present study demonstrates that a rational combination of prodrug design and formulation strategies can effectively deliver THC to the anterior chamber of the eye. An increased IOP reduction with the prodrug at lower equivalent doses of THC, supports improved ocular penetration of the prodrug. Importantly, with most of the conventionally developed anti-glaucoma drugs having no reported neuroprotective action, THC, an established neuroprotectant, has the potential to become an effective glaucoma medication. Further studies are currently aimed at developing and optimizing various formulations with improved THC delivery to the back-of-the eye. Since the rate of elimination of drug candidates was relatively rapid in the earlier studies, ion exchange resin - drug complexes were incorporated into the matrix film to improve the sustained release profile. Ion exchange resins (IR) are water insoluble cross linked polymers with ionizable groups that can be exchanged to form complexes. Diclofenac sodium (DFS) was used as a model drug. The goal of this study was to develop polymeric matrix films loaded with a combination of free diclofenac sodium (DFS) and DFS-Ion exchange resin (IR) complexes for immediate and sustained release profiles, respectively. Complexation efficiency of DFS-IR was found to be 99% at 1:1 ratio of DFS:IR. Solution and DFS:IR suspension formulations were not able to maintain therapeutic DFS levels in AH and other ocular tissues. The matrix film, as such, was able to achieve high levels of DFS in the ocular tissues, but was not able to overcome the rapid elimination profile. On the other hand, DFS:IR loaded matrix films were able to maintain DFS levels in the inner ocular tissues fairly constant for upto 8h, probably because of continuous release of DFS from the IR and retention of the IR complexes on the ocular surface. Thus, drug IR complexes loaded into matrix films could be a potential sustained ocular delivery platform

Diclofenac sodium ion exchange resin complex loaded melt cast films for sustained release ocular delivery

The goal of the present study is to develop polymeric matrix films loaded with a combination of free diclofenac sodium (DFSfree) and DFS:Ion exchange resin complexes (DFS:IR) for immediate and sustained release profiles, respectively. Effect of ratio of DFS and IR on the DFS:IR complexation efficiency was studied using batch processing. DFS:IR complex, DFSfree, or a combination of DFSfree+DFS:IR loaded matrix films were prepared by melt-cast technology. DFS content was 20% w/w in these matrix films. In vitro transcorneal permeability from the film formulations were compared against DFS solution, using a side-by-side diffusion apparatus, over a 6 h period. Ocular disposition of DFS from the solution, films and corresponding suspensions were evaluated in conscious New Zealand albino rabbits, 4 h and 8 h post-topical administration. All in vivo studies were carried out as per the University of Mississippi IACUC approved protocol. Complexation efficiency of DFS:IR was found to be 99% with a 1:1 ratio of DFS:IR. DFS release from DFS:IR suspension and the film were best-fit to a Higuchi model. In vitro transcorneal flux with the DFSfree+DFS:IR(1:1)(1 + 1) was twice that of only DFS:IR(1:1) film. In vivo, DFS solution and DFS:IR(1:1) suspension formulations were not able to maintain therapeutic DFS levels in the aqueous humor (AH). Both DFSfree and DFSfree+DFS:IR(1:1)(3 + 1) loaded matrix films were able to achieve and maintain high DFS concentrations in the AH, but elimination of DFS from the ocular tissues was much faster with the DFSfree formulation. DFSfree+DFS:IR combination loaded matrix films were able to deliver and maintain therapeutic DFS concentrations in the anterior ocular chamber for up to 8 h. Thus, free drug/IR complex loaded matrix films could be a potential topical ocular delivery platform for achieving immediate and sustained release characteristics

Access to Contraceptive Services during the COVID-19 Pandemic: Perceptions of Choose Well Hospital Partners

Introduction: Contraceptive decision-making is individual in nature and access to high-quality contraceptive care, including counseling and the full range of contraceptive methods, can help individuals achieve their personal reproductive goals and prevent unintended pregnancy. The COVID-19 pandemic disrupted provision and utilization of contraceptive counseling and contraceptive methods. Long-acting reversible contraception (LARC) methods, such as the contraceptive implant and intrauterine devices (IUDs), were particularly affected by the pandemic because they require placement by a health care provider in a clinical setting. Choose Well (CW), an ongoing statewide contraceptive access initiative in South Carolina, launched in 2017 and continues through 2022. CW aims to implement best practices of contraceptive care via training and funding for IUD and implant methods. This study examined the perceptions of access to contraceptive counseling and implant and IUD methods during the pandemic in 2020 among CW hospital partners. Methods: Data were collected in 2021 via key informant interviews with partners (n=9) at CW implementing hospitals to assess perceptions of CW activities in 2020, the first year of the COVID-19 pandemic. A semi-structured interview guide was used, and interviews were recorded, transcribed, and consensus coded. A codebook was developed based on the interview guide. Data from select questions of interest related to perceived access to contraceptive counseling, access to LARC methods, and the impact of the pandemic on contraceptive care services were analyzed for this study. Coding was conducted with NVivo software version 1.6.1. Results: Findings show that there was continued provision of contraceptive services during COVID-19 at CW partner hospitals, including an increase in access to contraceptive counseling and LARCs in 2020. The most prevalent facilitator for increased access to contraceptive counseling and LARCs at CW partner hospitals was having key personnel available such as physicians and Obstetrics (OB) navigators. Expanded access to outpatient sites was also noted as a facilitator of contraceptive counseling. Advertising and wide-spread patient education, buy-in and engagement from staff were additional facilitators for the increased access to LARCs. Considering the context of the COVID-19 pandemic, patients wanting to quickly leave the hospital and challenges with staffing contributed to an overall decline in access in some hospital locations. Challenges with staffing included not being able to receive training and nurses being overworked and overburdened. Conclusion: While COVID-19 has posed challenges to contraceptive care service provision, most individuals perceived an increase in access to contraceptive counseling and LARCs at CW partner hospitals. Hospital partners have continued to provide contraceptive services during COVID-19. The findings suggest the success of the CW initiative in increasing access to contraceptive services, particularly during COVID-19 through key facilitators. Staffing positions such as OB Navigators should be funded and maintained to increase access to contraceptive care services in hospital inpatient settings. Coordinating care between hospital inpatient and outpatient settings is similarly important for widespread patient education about contraceptive care services

Enantioselective metabolism of primaquine by human CYP2D6

BACKGROUND: Primaquine, currently the only approved drug for the treatment and radical cure of Plasmodium vivax malaria, is still used as a racemic mixture. Clinical use of primaquine has been limited due to haemolytic toxicity in individuals with genetic deficiency in glucose-6-phosphate dehydrogenase. Earlier studies have linked its therapeutic effects to CYP2D6-generated metabolites. The aim of the current study was to investigate the differential generation of the CYP2D6 metabolites by racemic primaquine and its individual enantiomers. METHODS: Stable isotope (13)C-labelled primaquine and its two enantiomers were incubated with recombinant cytochrome-P450 supersomes containing CYP2D6 under optimized conditions. Metabolite identification and time-point quantitative analysis were performed using LC-MS/MS. UHPLC retention time, twin peaks with a mass difference of 6, MS-MS fragmentation pattern, and relative peak area with respect to parent compound were used for phenotyping and quantitative analysis of metabolites. RESULTS: The rate of metabolism of (+)-(S)-primaquine was significantly higher (50% depletion of 20 μM in 120 min) compared to (−)-(R)-primaquine (30% depletion) when incubated with CYP2D6. The estimated V(max) (μmol/min/mg) were 0.75, 0.98 and 0.42, with K(m) (μM) of 24.2, 33.1 and 21.6 for (±)-primaquine, (+)-primaquine and (−)-primaquine, respectively. Three stable mono-hydroxylated metabolites, namely, 2-, 3- and 4-hydroxyprimaquine (2-OH-PQ, 3-OH-PQ, and 4-OH-PQ), were identified and quantified. 2-OH-PQ was preferentially formed from (+)-primaquine in a ratio of 4:1 compared to (−)-primaquine. The racemic (±)-primaquine showed a pattern similar to the (−)-primaquine; 2-OH-PQ accounted for about 15–17% of total CYP2D6-mediated conversion of (+)-primaquine. In contrast, 4-OH-PQ was preferentially formed with (−)-primaquine (5:1), accounting for 22% of the total (−)-primaquine conversion. 3-OH-PQ was generated from both enantiomers and racemate. 5-hydroxyprimaquine was unstable. Its orthoquinone degradation product (twice as abundant in (+)-primaquine compared to (−)-primaquine) was identified and accounted for 18–20% of the CYP2D6-mediated conversion of (+)-primaquine. Other minor metabolites included dihydroxyprimaquine species, two quinone-imine products of dihydroxylated primaquine, and a primaquine terminal alcohol with variable generation from the individual enantiomers. CONCLUSION: The metabolism of primaquine by human CYP2D6 and the generation of its metabolites display enantio-selectivity regarding formation of hydroxylated product profiles. This may partly explain differential pharmacologic and toxicologic properties of primaquine enantiomers