An UPLC-MS/MS Method for Simultaneous Determination of Tropicamide and Phenylephrine in Rabbit Ocular Tissues and Plasma.

Purpose: Mixed eye drops containing 0.5% tropicamide and 0.5% phenylephrine are commercially available for cycloplegic refraction. Determining the pharmacokinetics (PK) and distribution of tropicamide and phenylephrine simultaneously in ocular tissues is an important but challenging issue. Herein, we developed a sensitive and selective ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) method for simultaneous determination of tropicamide and phenylephrine concentrations in rabbit ocular tissues and plasma. Methods: The two analytes were extracted with ethyl acetate using etofesalamide as an internal standard and separated using a chromatographic C8 column with isocratic elution. Mass spectrometry analysis was performed with positive electrospray ionization and data were acquired in a multiple reaction monitoring mode. Results: We validated this method over a concentration range of 5-1,600 ng/mL for tropicamide and 1-320 ng/mL for phenylephrine in ocular tissues, as well as 0.5-64 ng/mL for both compounds in plasma. Inter- and intraday precisions in all samples were both <12.9% and the accuracy was within 92.1%-108.4%. The highest concentration of tropicamide was found in aqueous humor (Cmax: 29430 ng/g), while was in cornea for phenylephrine (Cmax: 3465 ng/g). All the ocular tissues concentrations were much higher than those of blood. Conclusion: This UPLC-MS/MS method allowed us to determine the PK and distribution of tropicamide and phenylephrine in rabbit ocular tissue, which may be helpful in the future development and application of mydriatic agents.

Potential cardiovascular adverse events when phenylephrine is combined with paracetamol: simulation and narrative review.

BACKGROUND: Increased bioavailability of phenylephrine is reported when combined with paracetamol in over-the-counter formulations for the symptomatic treatment of the common cold and influenza. Such formulations could increase phenylephrine-related cardiovascular adverse events particularly in susceptible individuals. Quantification of the effect of phenylephrine concentration on blood pressure allows simulation of potential adverse combination therapy effects. METHODS: MEDLINE and EMBASE databases were searched for papers discussing or describing any adverse effect, hypersensitivity or safety concerns related to phenylephrine alone or in combination with other drugs. The pharmacodynamic relationship between plasma phenylephrine concentration and mean arterial blood pressure was characterized using published observations of blood pressure changes after ophthalmic eye drops. The resulting pharmacokinetic and pharmacodynamic parameters were then used to predict mean arterial blood pressure (MAP) changes in that population if given an oral combination of phenylephrine and paracetamol. RESULTS: There were 1172 papers identified for examination. Forty-seven reports fulfilled the inclusion criteria. Increases in blood pressure and decreases in heart rate have been reported with doses over 15 mg. It has been estimated that a 20-mmHg increase in systolic blood pressure would occur with an oral dose of 45 mg phenylephrine in normotensive healthy people. Those taking monoamine oxidase inhibitors report increased systolic blood pressure of greater than 60 mmHg. Blood pressure and heart rate changes are potentiated in patients with underlying hypertension. Simulation showed a modest increase in MAP when phenylephrine 10 mg was co-administered with paracetamol 1 g (4.2 vs 12.3 mmHg). CONCLUSIONS: Combination paracetamol phenylephrine oral therapy has potential to increase blood pressure more than phenylephrine alone in those with cardiovascular compromise.

Use of hollow microneedles for targeted delivery of phenylephrine to treat fecal incontinence.

A hollow microneedle (HM) was prepared to deliver a phenylephrine (PE) solution into the anal sphincter muscle as a method for treating fecal incontinence. The goal of this study was the local targeted delivery of PE into the sphincter muscle through the perianal skin with minimal pain using hollow microneedles, resulting in the increase of resting anal sphincter pressure. PE was administered on the left and the right sides of the anus of a rat through the perianal skin using 1.5mm long HM. An in vivo imaging system study was conducted after injection of Rhodamine B, and a histological study was performed after injection of gentian violet. The resting anal sphincter pressure in response to various drug doses was measured by using an air-charged catheter. Anal pressure change produced by HM administration was compared with change produced by intravenous injection (IV), subcutaneous (SC) injection and intramuscular (IM) injection. The change in mean blood pressure produced by HM administration as a function of PE dose was compared with change produced by PBS injection. A pharmacokinetic study of the new HM administration method was performed. A model drug solution was localized in the muscle layer under the perianal skin at the injection site and then diffused out over time. HM administration of PE induced significant contraction of internal anal sphincter pressure over 12h after injection, and the maximum anal pressure was obtained between 5 and 6h. Compared to IV, SC and IM treatments, HM treatment produced greater anal pressure. There was no increase in blood pressure after HM administration of PE within the range of predetermined concentration. Administration of 800µg/kg of PE using HM produced 0.81±0.38h of tmax. Our study suggests that HM administration enables local delivery of a therapeutic dose of PE to the anal sphincter muscle layer with less pain. This new treatment has great potential as a clinical application because of the ease of the procedure, minimal pain, and dose-dependent response.

An in-vivo evaluation of a MEMS drug delivery device using Kunming mice model.

The use of MEMS implantable drug delivery pump device enables one to program the desired drug delivery profile in the device for individualized medicine treatment to patients. In this study, a MEMS drug delivery device is prepared and employed for in vivo applications. 12 devices are implanted subcutaneously into Kunming mice for evaluating their long term biocompatibility and drug-delivery efficiency in vivo. All the mice survived after device implantation surgery procedures. Histological analysis result reveals a normal wound healing progression within the tissues-to-device contact areas. Serum analysis shows that all measured factors are within normal ranges and do not indicate any adverse responses associated with the implanted device. Phenylephrine formulation is chosen and delivered to the abdominal cavity of the mice by using either the implanted MEMS device (experimental group) or the syringe injection method (control group). Both groups show that they are able to precisely control and manipulate the increment rate of blood pressure in the small animals. Our result strongly suggests that the developed refillable implantable MEMS devices will serve as a viable option for future individualized medicine applications such as glaucoma, HIV-dementia and diabetes therapy.

A randomised, controlled, crossover study to investigate the safety and response of 1R,2S-methoxamine hydrochloride (NRL001) on anal function in healthy volunteers.

AIMS: This study aimed to assess the dose and volume effects of suppository preparations and safety of NRL001 (one of four possible stereoisomers of methoxamine hydrochloride) on anal sphincter tone using rectal suppositories in healthy adult volunteers. METHODS: This was a Phase I, single-centre, randomised, double-blind, three-way crossover study during which subjects received three single doses of 1 g rectal suppositories (containing 5 or 10 mg NRL001 or matching placebo) or 2 g rectal suppositories (containing 10 or 15 mg NRL001 or matching placebo) on three separate dosing days. The outcome measures were mean anal resting pressure (MARP) variables (monitored continuously for 20-30 min before and up to 6 h after dosing), pharmacokinetics (PK) and safety assessments. RESULTS: Twenty-six subjects were dosed with study medication. Two subjects were withdrawn prematurely and were not included in the main analysis. There was a dose-dependent increase in anal sphincter tone (MARP) when comparing the 5 and 10 mg doses of NRL001; however, the 15 mg dose did not have a significantly greater effect than the 10 mg dose. Suppository size (1 or 2 g) did not appear to have an effect on sphincter tone. There was no evidence against dose proportionality for the PK variables, but the mean maximum plasma concentration (Cmax ) for the 1 g suppository group was higher than for the 2 g group. Twenty-one adverse events were reported in 8 (30.8%) subjects. A dose dependent decrease in heart rate was noted; however, there were no adverse events reported that were related to this reduction in heart rate. CONCLUSIONS: The increase in anal sphincter tone supports the potential therapeutic use of NRL001 in treating faecal incontinence, with further studies in patients required. NRL001 was well tolerated in single doses of up to 15 mg.

Randomised clinical trial: study of escalating doses of NRL001 given in rectal suppositories of different weights.

AIMS: The application of α-adrenoceptor agonists can improve faecal incontinence symptoms. The aim of this study was to investigate the pharmacokinetic and systemic effects of NRL001 administered as different strengths in 1 or 2 g suppositories. METHODS: This randomised, double-blind, placebo controlled study included 48 healthy subjects. Group 1 consisted of two cohorts of 12 subjects administered either four single doses of 1 or 2 g rectal suppository with either 5, 7.5 or 10 mg NRL001, or matching placebo. Group 2 consisted of two cohorts of 12 subjects administered either four single doses of 1 or 2 g rectal suppository with either 10, 12.5 or 15 mg NRL001, or matching placebo. Doses were given in an escalating manner with placebo at a random position within the sequence. RESULTS: Tmax was at ~4.5 h post-dose for all NRL001 doses. Median AUC0-tz , AUC0-∞ and Cmax increased with increasing dose for both suppository sizes. The estimate of ratios of geometric means comparing 2 g with 1 g suppository, and regression analysis for dose proportionality, was close to 1 for the variables AUC0-tz , AUC0-∞ and Cmax (P > 0.05). For both suppository sizes, 20-min mean pulse rate was significantly decreased compared with placebo with all doses (P < 0.05). Blood pressure decreased overall. There were 144 adverse events (AEs) and no serious AEs reported during the study. All AEs were mild in severity. CONCLUSIONS: The regression analysis concluded that the doses were dose proportional.

A randomised, controlled, crossover study to investigate the pharmacodynamics, pharmacokinetics and safety of 1R,2S-methoxamine hydrochloride (NRL001) in healthy elderly subjects.

AIMS: This study aimed to assess the effects of a single dose of 10 mg NRL001 (the 1R,2S stereoisomer of methoxamine hydrochloride) in a 2 g suppository on pharmacodynamic and pharmacokinetic (PK) variables, and safety, in a healthy elderly population. METHODS: This was a Phase I, single-centre, randomised, double-blind, placebo-controlled crossover study during which subjects received a single 2 g suppository of 10 mg NRL001 and a matching placebo in two separate treatment periods. The main outcome measures were Holter-, vital signs- and electrocardiogram-derived cardiovascular variables; plasma PK analysis; and safety assessments. RESULTS: Twenty-six subjects were dosed with study medication. Statistically significant reductions in Holter-derived heart rate (HR), vital signs-derived HR and diastolic blood pressure (BP) were observed comparing NRL001 with placebo treatment, and also with increasing NRL001 plasma concentration. No statistically significant relationships were observed between NRL001 concentration and systolic BP, mean arterial pressure or QTC interval (both Bazett's and Fridericia's correction). Thirty-nine adverse events were reported in 20 (76.9%) subjects, mostly after dosing with NRL001. CONCLUSION: Administration of NRL001 suppositories led to decreases in HR when compared with placebo data. NRL001 was well tolerated with a good safety profile during the study. Healthy elderly subjects did not show significantly different biological responses to NRL001 suppositories compared with younger healthy volunteers in previous studies.

A double-blind, placebo-controlled, randomised, parallel-group, dose-escalating, repeat dose study in healthy volunteers to evaluate the safety, tolerability, pharmacodynamic effects and pharmacokinetics of the once daily rectal application of NRL001 suppositories for 14 days.

AIMS: The 1R,2S stereoisomer of methoxamine hydrochloride, NRL001, is a highly selective α1-adrenoceptor agonist being developed for the local treatment of non-structural faecal incontinence caused by weak internal anal sphincter tone. This study investigated the steady state pharmacokinetics (PK) and safety of 2 g rectal suppositories containing NRL001 in different strengths (7.5, 10, 12.5 or 15 mg). METHODS: Healthy volunteers aged 18-45 years received 14 daily doses of NRL001 2 g suppositories or matching placebo. In each dose group nine participants received NRL001 and three received placebo. Blood samples to determine NRL001 concentrations were taken on Days 1, 7 and 14. Cardiovascular parameters were collected via electrocardiograms, Holter monitoring (three lead Holter monitor) and vital signs. RESULTS: Forty-eight volunteers were enrolled; 43 completed the study and were included in the PK analysis population. AUC and Cmax broadly increased with increasing dose, Tmax generally occurred between 4.0 and 5.0 h. Although the data did not appear strongly dose proportional, dose proportionality analysis did not provide evidence against dose proportionality as the log(dose) coefficients were not significantly < 1. NRL001 did not accumulate over time for any dose. Increasing NRL001 concentrations were related to changes in vital sign variables, most notably decreased heart rate. The most commonly reported adverse events (AEs) in the active treatment groups were paraesthesia and piloerection. CONCLUSIONS: Treatment with NRL001 was generally well tolerated over 14 days once daily dosing and plasma NRL001 did not accumulate over time. Treatment was associated with changes in vital sign variables, most notably decreased heart rate. AEs commonly reported with NRL001 treatment were events indicative of a systemic α-adrenergic effect.

Libertas: rationale and study design of a multicentre, Phase II, double-blind, randomised, placebo-controlled investigation to evaluate the efficacy, safety and tolerability of locally applied NRL001 in patients with faecal incontinence.

AIMS: Faecal incontinence affects up to 8% of adults. Associated social isolation and subsequent depression can have devastating effects on quality of life (QoL). Faecal incontinence is an underreported health problem as the social isolation and stigma that patients experience makes it difficult for sufferers to discuss their condition with a physician. There have been few well-designed, placebo-controlled clinical trials of treatment for faecal incontinence and little clinical evidence is available to inform the most appropriate management strategies. Libertas, a robustly designed study will investigate the efficacy and safety of NRL001 (1R,2S-methoxamine), an α1 -adrenoceptor agonist, in the treatment of faecal incontinence. METHODS: Libertas is a multicentre, Phase II, double-blind, randomised, placebo-controlled, parallel group study. Patient recruitment took place across 55 study centres in Europe. Patients suffering with faecal incontinence were randomised into four groups (approximately 110 each) to receive once daily self-administered doses of NRL001 (5, 7.5 or 10 mg or placebo in a suppository formulation) for 8 weeks. The primary objective of Libertas is to assess the impact of once daily administration of NRL001 on the severity and frequency of incontinence episodes as assessed by the Wexner score at 4 weeks, compared with placebo. Secondary outcomes include measures of efficacy of NRL001 compared with placebo following 8 weeks treatment; safety and tolerability; evaluation of plasma pharmacokinetics; establishment of any pharmacokinetic/pharmacodynamic relationship to adverse events; dose-response relationship; the efficacy of NRL001 therapy at 4 and 8 weeks assessed by the Vaizey score; and QoL using the Faecal Incontinence Quality of Life and the EQ-5D-5L Healthcare Questionnaires following 4 and 8 weeks NRL001 therapy. Overall patient satisfaction with the treatment will also be evaluated. DISCUSSION: This is the first randomised controlled study to investigate the efficacy and safety of a selective α1 -adrenoceptor agonist for the treatment of faecal incontinence. Furthermore, this is the first time the impact of NRL001 on assessments of QoL, health outcomes and patient satisfaction will be assessed. Innovative strategies were developed to meet the challenge of recruiting patients for this study, for example, media advertising, posters and mailshots as allowed by each study centre.

Structural identifiability analysis and reparameterisation (parameter reduction) of a cardiovascular feedback model.

Structural identifiability should be considered when developing mathematical models. A globally or at least locally identifiable model has to be obtained in order to have some chance of obtaining unique parameter estimates when real data are available. An indicator of structural unidentifiability may be that some unknown parameter estimates are found to be not well determined from parameter estimation of a model. An example is discussed in this paper to illustrate the procedures involved when such situations arise. Problems with parameter estimation were observed for a PKPD model for an α1A/1L-adrenoceptor partial agonist developed for the treatment of stress urinary incontinence The regulation of the side effects of the increased peripheral resistance, induced by the constriction of the blood vessels, was modelled by adapting a previous cardiovascular nonlinear PKPD model proposed by Franchetau and co-workers. Structural identifiability analysis confirmed that the model was unidentifiable. The model was then reparameterised (parameter list reduction) to obtain a globally identifiable model. Simulation studies confirm the superiority of the reduced parameterisation with respect to parameter estimation. The simulation study also confirms the models behave indistinguishably with respect to the input-output behaviour. The example demonstrates the importance of recognising an unidentifiable model and illustrates step by step identifiability analysis, reparameterisation and validation of reparameterised model against the original model.

The efficacy and safety of PSD503 (phenylephrine 20%, w/w) for topical application in women with stress urinary incontinence. A phase II, multicentre, double-blind, placebo controlled, 2-way cross over study.

OBJECTIVE: PSD503 is a topical gel containing phenylephrine 20% weight/weight (w/w) intended for vaginal application close to the area of the urethral sphincter in women with SUI and has been used in patients with faecal incontinence. The primary objective of this proof of concept study was to evaluate the efficacy of PSD503 in women with SUI as measured by the change in pad weight following an exercise stress pad test. The secondary objectives were to evaluate plasma concentrations of PSD503, BP changes and pulse rate over 3h following administration and to assess safety and tolerability. STUDY DESIGN: This was a phase II multi-centre, double-blind, placebo-controlled, 2 way cross-over study. Women were assessed objectively pre and post PSD503 administration using a standardised exercise stress pad test. Safety was assessed by monitoring pulse, BP and plasma levels of PSD503 over 3h following administration. A power calculation suggested a >80% power to demonstrate (at the 5% level of significance) a difference between treatments of 10-20g with a sample size of 30 patients. RESULTS: 14 patients were screened and 12 patients randomised over 20 months. Projections indicated the study would not attain its full quota within 1 year and it was terminated early. Treatment with PSD503 resulted in a greater reduction in pad weight gain than placebo, when expressed as both a percentage change (median % change: placebo - 38.00%, PSD503 - 54.33%) and absolute change (median absolute change: placebo - 10.0g, 20% (w/w) PSD503 - 22.0g) from pre-dose leakage. PSD503 was absorbed into the blood within 1h (median concentration 1.490ng/ml). Plasma concentrations at 3h (median 1.305ng/ml) were less than that at 1h and lower than plasma concentrations seen following phenylephrine-containing cold remedies. There were no withdrawals, serious adverse events and it was well tolerated overall. CONCLUSION: This is the first proof of concept study to demonstrate that a topical α adrenergic agonist gel is rapidly and consistently absorbed vaginally and may have a role in the management of female SUI. However, since recruitment was difficult this may indicate that whilst objectively effective, acceptability in clinical practice may be poor.