Systemic absorption and anticholinergic activity of topically applied tropicamide

Tropicamide Versus Cyclopentolate for Cycloplegic Refraction in Pediatric Patients With Brown Irides: A Randomized Clinical Trial

PURPOSE

To compare the final cycloplegic refraction of tropicamide 1% and cyclopentolate 1% in children 3-16 years of age with brown irides.

DESIGN

Randomized, controlled, multicenter prospective clinical trial.

METHODS

Included patients were randomized to either cyclopentolate 1% or tropicamide 1% in the first visit with autorefraction measurements. Each subject underwent a second cycloplegic refraction using the other agent on a separate visit with a minimum of 1-week interval and a maximum of 12 weeks. We measured the change in SE (ΔSE) for each eye by deducting the SE before cycloplegia from the SE after cycloplegia.

RESULTS

A total of 185 eyes from 94 children aged 3-16 years (average= 8.79 ±3.11 years) were included. The average SE of both eyes before cycloplegia was -0.082 ± 4.8 diopters. The SE after instillation of cyclopentolate and tropicamide in both eyes was 1.07±5.2 and 0.96±5.1, respectively (P value < .001). The average ΔSE after cycloplegia was 1.15±1.2 for cyclopentolate and 1.04±1.2 for tropicamide (P value < .001). The difference between ΔSE of cyclopentolate and tropicamide was found statistically significant at 0.11±1.2 (P < .001), although clinically insignificant. The ΔSE between the 2 drops before and after cycloplegia in both eyes for all refractive error groups was clinically insignificant. The greatest effect of cyclopentolate and tropicamide was in hyperopic eyes with ΔSE of 1.54±1.4 and 1.39±1.4, respectively.

CONCLUSIONS

Tropicamide might be an effective and safe replacement for cyclopentolate in the refracting nonstrabismic pediatric population 3-16 years of age regardless of their refractive error status.

Effects of pupil dilation with topical 0.5% tropicamide on retinal vascular parameters assessed by VAMPIRE® software in healthy cats

Our study investigates the effects of mydriasis obtained with topical 0.5% tropicamide on retinal vascular parameters evaluated in cats using the retinal imaging software: Vascular Assessment and Measurement Platform for Images of the Retina (VAMPIRE®). Forty client-owned healthy adult cats were included in the study. Topical 0.5% tropicamide was applied to dilate only the right pupil. The left eye was used as a control. Before dilation (T0), infrared pupillometry of both pupils was performed and fundus oculi images were taken from both eyes. Right eye fundus images were then captured 30 min after topical application of tropicamide (T30), when mydriasis was achieved. The retinal vessel widths (3 arteries and 3 veins) were measured with VAMPIRE® in four standard measurement areas (SMA) identified with the letters A, B, C, D. Average value of the 3 vessel widths was used. After normality assessment, the t-test was used to analyse the mean difference in vascular parameters of the left and right eyes at T0 and T30, with p set <0.05. The two eyes showed no statistical differences in pupil and vascular parameter measurements at T0. At T30, only one artery measurement of the right eye (SMA A-peripapillary area) showed a small but statistically significant mean vasoconstriction of approximately 4%. The results indicate that local application of 0.5% tropicamide seems to be associated with a small retinal arteriolar vasoconstriction as assessed by VAMPIRE® in cats. However, this change is minimal, and should not affect the interpretation of the results when VAMPIRE® is used.

Efficacy and safety of intraoperative use of tropicamide 0.02%/phenylephrine0.31%/lidocaine1% intracameral combination during pediatric cataract surgery

BACKGROUND

To demonstrate the safety and efficacy of the intracameral use of tropicamide 0.02%/phenylephrine 0.31%/lidocaine 1% in pediatric cataract surgery, a combination widely used in adult patients but still off-label in children.

METHODS

Design: two-center, prospective, observational study.

SETTING

San Giuseppe Hospital, Milan and Meyer Children's Hospital, Florence.

STUDY POPULATION

children from 0 to 4 years of age undergoing cataract surgery with or without intraocular IOL implantation, in the absence of clinically significant systemic conditions, history of ocular surgery, concurrent ocular medication, hypersensitivity to any of the substances and post-traumatic cataracts. During the surgery, patients received the combination drug after the primary access to the anterior chamber. Efficacy was evaluated by achieving an adequate mydriasis in order to perform capsulorhexis, while safety was assessed by recording vital signs (heart rate, blood pressure, respiratory rate, temperature) pre- and post-administration of the substance.

RESULTS

This study included 53 surgical procedures of 36 patients: 41 eyes were left aphakic, while 12 eyes received primary IOL implantation. The pupil size was adequate to safely perform capsulorhexis in 52 procedures of 53. The difference in pupil enlargement was significant (6.0 ± 1.14 mm, P =  < 0.001). There were no notable changes in vital parameters.

CONCLUSIONS

The administration of intracameral tropicamide 0.02%/phenylephrine 0.31%/lidocaine 1% in pediatric cataract surgery is effective for obtaining an adequate mydriasis without any vital parameters changes throughout the procedure.

Pupillary Dilation in Research: More than Meets the Eye

Purpose: Pupil dilation is a commonly used procedure in vision research. While often considered a minimal risk procedure, there is the potential for significant adverse effects. Methods: Currently, there is variance in practices and protocols among researchers and institutions, perhaps due to a lack of guidelines for safe pupil dilation practices in research settings. In this perspective, we explore variables that can increase the potential for adverse effects and provide suggestions to limit their impact. Prior to dilation, an investigator can assess an individual's medical status and drug regimen when deciding upon a mydriatic agent to be used. Results: Assessing the angle through a variety of methods (i.e. penlight test, van Herick slit lamp, optical coherence tomography, gonioscopy) can also prevent inappropriate dilation of pupils with concerning anatomical features. During dilation, an investigator should look to limit the potential of infection and use caution in repeat dosing of dilation-resistant pupils. Conclusions: Post-dilation, an investigator should closely monitor eyes with elevated risk factors and improve an individual's health literacy on angle closure complications. When combined with proper informed consent processes regarding adverse effects, the aforementioned can allow for risk mitigation in studies using pupil dilation.

The Expanding Role of Pyridine and Dihydropyridine Scaffolds in Drug Design

Pyridine-based ring systems are one of the most extensively used heterocycles in the field of drug design, primarily due to their profound effect on pharmacological activity, which has led to the discovery of numerous broad-spectrum therapeutic agents. In the US FDA database, there are 95 approved pharmaceuticals that stem from pyridine or dihydropyridine, including isoniazid and ethionamide (tuberculosis), delavirdine (HIV/AIDS), abiraterone acetate (prostate cancer), tacrine (Alzheimer's), ciclopirox (ringworm and athlete's foot), crizotinib (cancer), nifedipine (Raynaud's syndrome and premature birth), piroxicam (NSAID for arthritis), nilvadipine (hypertension), roflumilast (COPD), pyridostigmine (myasthenia gravis), and many more. Their remarkable therapeutic applications have encouraged researchers to prepare a larger number of biologically active compounds decorated with pyridine or dihydropyridine, expandeing the scope of finding a cure for other ailments. It is thus anticipated that myriad new pharmaceuticals containing the two heterocycles will be available in the forthcoming decade. This review examines the prospects of highly potent bioactive molecules to emphasize the advantages of using pyridine and dihydropyridine in drug design. We cover the most recent developments from 2010 to date, highlighting the ever-expanding role of both scaffolds in the field of medicinal chemistry and drug development.

Characterizing Current Attitudes and Practices for Human Subject Safety in Studies Involving Pupil Dilation

Standards in pupil dilation practices regarding the safety of human subjects are not present in vision research despite the potential for significant adverse effects. We developed two surveys to examine current practices around pupil dilation among vision researchers and individuals associated with oversight of human subjects research. While both groups note an absence of adverse events associated with pupil dilation, vision researcher practices differed with informed consent use and measures taken to minimize complications. For Institutional Review Boards, general risk assumption associated with dilation was not unanimous and there was a lack of specific guidance available to researchers for minimizing risk. These results uncover the need for standardized practices regarding pupil dilation in human subjects research.

Effect of Pupil Dilation with Tropicamide on Retinal Vascular Caliber

Purpose: The retinal blood vessels reflect changes in the brain's micro-circulation and these changes have been shown to correlate with the incidence of diseases such as stroke, heart disease and Alzheimer's disease. Studies investigating the retinal vasculature routinely use pupil dilation with tropicamide to optimize image acquisition and quality. The aim of this study was to investigate the effects of tropicamide on retinal vascular parameters using retinal photography.Methods: The study was performed on 41 healthy young subjects of both sexes, using tropicamide to dilate only the right pupil, leaving the left as a control.Results: Pupil dilation with tropicamide resulted in reduced retinal vessel width measures based on standardized approaches, particularly reduced arteriolar caliber (p < .0005). However, closer investigation of the images revealed reduced fundus image magnification in the post-tropicamide images, based on reduced optic nerve head diameter (p < .0005) and longitudinal analysis with image registration and affine transformation (p < .0001). No change in vessel width parameters was observed after adjustment for image magnification.Conclusion: These results suggest that tropicamide does not change the width of the retinal vessels, however width parameters as measured by standard approaches may be reduced due to image magnification changes resulting from cycloplegia. In this study, improved optic nerve head segmentation for image scale conversion removed the magnification error. With this correction, the tropicamide intervention had no effect on vessel width parameters in young healthy people and could be utilized in future without affecting the results of retinal vascular analysis.

DARK Classics in Chemical Neuroscience: Atropine, Scopolamine, and Other Anticholinergic Deliriant Hallucinogens

Anticholinergic drugs based on tropane alkaloids, including atropine, scopolamine, and hyoscyamine, have been used for various medicinal and toxic purposes for millennia. These drugs are competitive antagonists of acetylcholine muscarinic (M-) receptors that potently modulate the central nervous system (CNS). Currently used clinically to treat vomiting, nausea, and bradycardia, as well as alongside other anesthetics to avoid vagal inhibition, these drugs also evoke potent psychotropic effects, including characteristic delirium-like states with hallucinations, altered mood, and cognitive deficits. Given the growing clinical importance of anti-M deliriant hallucinogens, here we discuss their use and abuse, clinical importance, and the growing value in preclinical (experimental) animal models relevant to modeling CNS functions and dysfunctions.

Effects of two concentrations of topical tropicamide on the Schirmer tear test in clinically normal cats

Objectives

The aim of this study was to evaluate the effect of topical tropicamide at two concentrations (0.5% and 1.0%) on the Schirmer tear test (STT) results in clinically normal cats.

Methods

Twenty-four adult domestic shorthair cats were randomly assigned to three groups. In all three groups, ophthalmic solutions were instilled in a randomly selected eye and the opposite eye served as the control. In groups 1, 2 and 3 one drop of 0.5% tropicamide, 1.0% tropicamide and distilled water was used, respectively. Tear production in both eyes was tested 30 and 60 mins after instillation in all three groups.

Results

Baseline mean ± SEM STT values for the treated eyes in groups 1, 2 and 3 were 13.37 ± 2.91 mm/min, 10.87 ± 1.39 mm/min and 11.37 ± 1.65 mm/min, respectively. Thirty minutes after the drug instillation in the treated eye, mean ± SEM STT values in groups 1, 2 and 3 were 4.87 ± 3.05 mm/min, 2.00 ± 0.84 mm/min and 11.25 ± 1.81 mm/min, respectively. The mean ± SEM STT levels of the treated eye after 60 mins were 3.75 ± 1.87 mm/min, 0.5 ± 0.37 mm/min and 11.42 ± 1.78 mm/min in groups 1, 2 and 3, respectively.

Conclusions and relevance

Use of 0.5% topical tropicamide, instead of 1.0% tropicamide, as a mydriatic agent, can be recommended in cats. Tear production measurement should be performed prior to the administration of tropicamide, regardless of the concentration of this drug.

[Serious adverse side effects after pupillary dilation in preterm infants]

PURPOSE

This study aimed at investigating serious side effects of the pupillary dilation protocol used in Caen University Hospital for the screening of retinopathy of prematurity. This protocol includes one drop of phenylephrine 5% and two drops of tropicamide 0.5% instilled at a 5-minute interval.

PATIENTS AND METHODS

This retrospective study included all premature infants with a birth weight less than or equal to 1500 g and/or a gestational age less than or equal to 30 gestational weeks, hospitalized in the neonatal intensive care unit of Caen University Medical Center, having ocular fundus examinations for retinopathy of prematurity screening between 2009 and 2014. The medical records of patients who died or developed necrotizing enterocolitis were reviewed to analyze the imputability of the two eye drops used for pupil dilation.

RESULTS

Five-hundred and twelve infants were included, corresponding to 1033 ocular fundus examinations. No case of death could be ascribed to the use of eye drops. Two cases of necrotizing enterocolitis could be ascribed to the use of tropicamide with a doubtful and plausible intrinsic imputability according to French imputability criteria.

CONCLUSION

The pupillary dilation protocol used in Caen University Hospital for screening of retinopathy of prematurity might be implicated in two cases of necrotizing enterocolitis with an uncertain imputability of tropicamide 0.5% eye drops. No serious side effect could be ascribed to the use of phenylephrine 5% eye drops in this study.

Transient ileus associated with the use of mydriatics after screening for retinopathy of prematurity in a very low birth weight infant

Very low birth weight (VLBW) infants have ophthalmologic examinations for retinopathy of prematurity (ROP) prior to discharge, with appropriate follow-up and intervention where appropriate. Eye drops such as cylopentolate, tropicamide, and phenylephrine are used at different concentrations to provide proper pupil dilation for screening ROP. Topical instillation of eye drops may cause mild or severe ocular or systemic adverse effects. Early recognition of systemic toxicity after eye drop instillation is important. The authors present a case of a VLBW infant who developed significant abdominal symptoms (mimicking ileus) that were significant enough to discontinue oral feeding after ocular instillation of 0.5% tropicamide and 2.5% phenylephrine eye drops for routine examination of ROP. After structural and functional gastrointestinal disorders and sepsis were excluded, symptoms resolved completely after discontinuation of the drug. This report is thought to be the first in the medical literature to address 5% tropicamide and 2.5% phenylephrine eye drops, and the combination that may lead to serious complication after ROP examinations.

The investigation of the interaction between Tropicamide and bovine serum albumin by spectroscopic methods

The fluorescence and ultraviolet-visible (UV-Vis) spectroscopy were explored to study the interaction between Tropicamide (TA) and bovine serum albumin (BSA) at three different temperatures (292, 301 and 310K) under imitated physiological conditions. The experimental results showed that the fluorescence quenching mechanism between TA and BSA was static quenching procedure. The binding constant (Ka), binding sites (n) were obtained. The corresponding thermodynamic parameters (ΔH, ΔS and ΔG) of the interaction system were calculated at different temperatures. The results revealed that the binding process is spontaneous, hydrogen binds and vander Waals were the main force to stabilize the complex. According to Förster non-radiation energy transfer theory, the binding distance between TA and BSA was calculated to be 4.90 nm. Synchronous fluorescence spectroscopy indicated the conformation of BSA changed in the presence of TA. Furthermore, the effect of some common metal ions (Mg(2+), Ca(2+), Cu(2+), and Ni(2+)) on the binding constants between TA and BSA were examined.

Effects of unilateral topical administration of 0.5% tropicamide on anterior segment morphology and intraocular pressure in normal cats and cats with primary congenital glaucoma

OBJECTIVE

To determine the effects of topical 0.5% tropicamide on anterior segment morphology (ASM) and intraocular pressure (IOP) in normal and glaucomatous cats. ANIMALS USED: Normal cats and cats with inherited primary congenital glaucoma (PCG).

PROCEDURES

Control IOP curves were performed in untreated normal and PCG cats. In the first experiment, tropicamide was applied OD in eight normal and nine PCG cats. IOP and pupillary diameter (PD) were measured at 0, 30, and 60 min, then hourly until 8 h post-treatment. In a second experiment, six normal and seven PCG cats received tropicamide OD. High-resolution ultrasound images were obtained at 0, 1, 5, and 10 h post-treatment to measure ASM changes. IOP and PD were measured OD at 0, 1, 2, 3, 5, 7, and 9 h.

RESULTS

In untreated normal cats IOP OU decreased throughout the day. In PCG cats IOP OU had wide fluctuations over time. In normal cats IOP response varied in the treated eye but did not change significantly in untreated eyes. IOP significantly increased from baseline in both eyes of all treated PCG cats. Increases in IOP were associated with some ASM changes. Cats with PCG had a significantly smaller angle recess areas, diminished ciliary clefts and decreased iris-lens contact. ASM changes were not strongly correlated with IOP in all cats.

CONCLUSIONS

The ASM of PCG cats is markedly different from normal cats, and clinically significant increases in IOP OU occur in cats with PCG after tropicamide treatment. The mechanism for this increase remains unclear.

The modulation of fragile X behaviors by the muscarinic M4 antagonist, tropicamide

Muscarinic acetylcholine receptors (mAChR) are G protein-coupled receptors (M1-M5), grouped together into two functional classes, based on their G protein interaction. Although ubiquitously expressed in the CNS, the M4 protein shows highest expression in the neostriatum, cortex, and hippocampus. Electrophysiological and biochemical studies have provided evidence for overactive mAChR signaling in the fragile X knock-out (Fmr1KO) mouse model, and this has been hypothesized to contribute to the phenotypes seen in Fmr1KO mice. To address this hypothesis we used an M4 antagonist, tropicamide, to reduce the activity through the M4 mAChR and investigated the behavioral response in the Fmr1KO animals. Data from the marble-burying assay have shown that tropicamide treatment resulted in a decreased number of marbles buried in the wild-type (WT) and in the knockout (KO) animals. Results from the open field assay indicated that tropicamide increases activity in both the WT and KO mice. In the passive avoidance assay, tropicamide treatment resulted in the improvement of performance in both the WT and the KO animals at the lower doses (2 and 5 mg/kg), and the drug was shown to be important for the acquisition and not the consolidation process. Lastly, we observed that tropicamide causes a significant decrease in the percentage of audiogenic seizures in the Fmr1KO animals. These results suggest that pharmacological antagonism of the M4 receptor modulates select behavioral responses in the Fmr1KO mice.

A double-blind, placebo-controlled, randomized, crossover pilot study of the safety and efficacy of multiple doses of intra-oral tropicamide films for the short-term relief of sialorrhea symptoms in Parkinson's disease patients

OBJECTIVE

This proof-of-concept, pilot study aimed to explore the safety and anti-sialorrhea efficacy of single doses of intra-oral slow dissolving thin films containing tropicamide (NH004) or placebo.

METHODS

Nineteen non-demented, idiopathic stable or fluctuating PD patients who complained of sialorrhea received 3 doses (0.3, 1, 3mg) of tropicamide and placebo in random order, separated by 7 days. A 10-cm visual analog scale (VAS) was used to measure the patient's subjective feelings of saliva levels at baseline and at 15, 30, 45, 90 and 120 min after treatment administration. For the last 7 patients, saliva volume was measured at baseline and 75 min after treatment. Fluctuating patients were evaluated in the ON-condition.

RESULTS

The mean age of included patients was 67±12 years, 78% were male. Median disease duration was 8 years. The mean decrease in VAS score from baseline to 120 min were -0.55±0.54, -1.08±0.54, -1.53±0.52 and -0.81±0.51 for placebo and 0.3, 1 and 3mg tropicamide, respectively (F=0.6 p=0.6, ANOVA). Tropicamide 1mg resulted in a significant VAS score decrease (95%CI: -2.57 to -0.48). Saliva volume was reduced by 27%, 33% or 20% after tropicamide 0.3, 1 or 3mg vs 5% with placebo (p=0.5, Friedman). No adverse events were detected in any of the treatment sequences.

DISCUSSION

Results of this pilot, proof-of-concept study show that NH004 was safe and exerted antisialorrhea effects worthy of further exploration.

The muscarinic receptor antagonist tropicamide suppresses tremulous jaw movements in a rodent model of parkinsonian tremor: possible role of M4 receptors

RATIONALE

Nonselective muscarinic acetylcholine antagonists have been used for several years as antiparkinsonian drugs. However, there are at least five subtypes of muscarinic receptor (M1-5). Neostriatal M4 receptors have been implicated in aspects of motor function, and it has been suggested that M4 antagonists could be used as treatments for parkinsonism.

OBJECTIVE

Currently, there is a lack of highly selective M4 antagonists that readily penetrate the blood brain barrier. Thus, the present studies focused upon the effects of tropicamide, a muscarinic acetylcholine receptor antagonist with moderate binding selectivity for the M4 receptor subtype.

MATERIALS AND METHODS

Tremulous jaw movements were used as a model of parkinsonian tremor in these studies, and the effects of tropicamide were compared with those of the nonselective muscarinic antagonist atropine.

RESULTS

Tropicamide suppressed the tremulous jaw movements induced by the muscarinic agonist pilocarpine and the dopamine antagonist pimozide. Analysis of the dose-response curves indicated that tropicamide showed approximately the same potency as atropine for suppression of pilocarpine-induced jaw movements but was more potent than atropine on the suppression of pimozide-induced jaw movements. In contrast, atropine was more potent than tropicamide in terms of impairing performance on visual stimulus detection and delayed nonmatch-to-position tasks.

CONCLUSIONS

These studies demonstrate that tropicamide, which currently is used clinically for ophthalmic purposes, can exert actions that are consistent with antiparkinsonian effects. Moreover, the different pattern of effects shown by tropicamide compared to those of atropine on motor vs cognitive tasks could be due to the modest M4 selectivity shown by tropicamide.

[The Mydriasert insert: an alternative to eye drops for preangiographic mydriasis]

PURPOSE

Mydriasert is an insoluble ophthalmic insert, gradually releasing two well-known active ingredients: phenylephrine and tropicamide. It is indicated in presurgical mydriasis. The purpose was to evaluate its efficacy in obtaining mydriasis required for fluorescein angiography.

MATERIAL AND METHODS

The ability of Mydriasert to provide mydriasis (defined by a pupillary diameter of at least 7 mm) compatible with a bilateral angiographic examination in optimal conditions was evaluated by a comparative, randomised versus active treatment (eye drops) open trial in 72 patients.

RESULTS

All the patients obtained a stable mydriasis allowing angiography. In the Mydriasert group, mydriasis preparation required a mean of 10 min more (Student t test: p<0.001); however, near eyesight recovery was 15 min shorter on average (log-rank test<0.01%) and amounts of active ingredients administered to provide mydriasis were 5-10 times higher in the eye drops reference group. Cardiovascular parameters remained in the normal range in both groups. Three patients of the Mydriasert group presented one ocular symptom of local intolerance, which disappeared in 15 min (exact Fisher test not significant between the treatment groups, p=0.2394). No superficial punctate keratitis was detected during the trial.

CONCLUSION

The treatment by Mydriasert can prepare preangiographic mydriasis as well as the reference treatment. The time required for mydriasis is slightly longer. Near eyesight recovery, faster with Mydriasert, could provide an improvement in patient safety and comfort at the end of the ophthalmologic visit.

Effects of topical 0.5% tropicamide on intraocular pressure in normal cats

The objective of the study was to determine the effect of topical 0.5% tropicamide on intraocular pressure (IOP) in normotensive feline eyes. IOP was measured bilaterally in 70 clinically healthy cats and gonioscopy (and goniophotography) was performed. Thereafter, 50 cats were treated unilaterally with one drop of 0.5% tropicamide. The contralateral, left eye served as a control. In the placebo group consisting of 20 cats, one drop of physiologic saline solution was administered to the right eye. In all cats, IOP of both eyes was measured 30, 60 and 90 min after topical administration. After unilateral tropicamide application, IOP increased significantly both in the right and in the left eye. Maximum average IOP increase was observed at the control measurement performed 90 min after treatment, with an elevation of 3.8 +/- 4.2 mmHg in the right eye and 3.5 +/- 3.6 mmHg in the left eye. Maximum IOP increase after treatment was 18.0 mmHg in the treated eye and 17.0 mmHg in the left eye. Measurements made at 60 min after treatment revealed a significantly higher increase in IOP in the right eye as compared to the left eye (P60 < 0.05), whereas the differences between right and left eye in IOP increase were not significant at 30 and 90 min after mydriatic application (P30 = 0.123; P90 = 0.305). Although tropicamide-induced mydriasis was observed in the treated eye, the contralateral eye did not show any changes in pupillary function at any time. With increasing age of the cats, IOP increase was found to be more moderate, whereas the gender of the cats did not have any significant influence on IOP changes. In the 20 cats in the placebo group, no significant changes in IOP were observed. We conclude that topical 0.5% tropicamide causes a significant elevation of IOP in the treated and untreated eye in normal cats.

Review on the systemic delivery of insulin via the ocular route

Systemic drug absorption from the ocular route is well known. Although there is some absorption from the conjunctival sac, the nasal meatus is the site where the majority of systemic absorption of instilled drug takes place. This article reviews the principles of systemic absorption of insulin applied topically to the eye. The physiological and pharmaceutical considerations for formulation development and the strategy of improving the systemic absorption and bioavailability of insulin are also discussed.

Near fatal anticholinergic intoxication after routine fundoscopy

We describe a case of severe anticholinergic intoxication following the topical instillation of tropicamide-containing eyedrops. Tropicamide is a short-acting atropine-like derivative and has been regarded as an effective and safe mydriatic. Half an hour after routine fundoscopy, a 62-year-old man experienced two generalized seizures with respiratory arrest and required intubation and mechanical ventilation. The patient was treated with physostigmine and made a full recovery.

Systemic and ocular absorption and antagonist activity of topically applied cyclopentolate in man

Ocular and systemic absorption and antagonist activity of topical 1% cyclopentolate were studied in 11 elderly patients undergoing extracapsular cataract extraction, and in 8 healthy female volunteers. The patients received two 35 microl drops of cyclopentolate unilaterally and the healthy volunteers one 30 microl drop bilaterally to the lower conjunctival cul-de-sac of the eye. The drug concentrations were measured with radioreceptor assay and receptor occupancies with radiooccupancy assay using isolated rat brain muscarinic cholinoceptors. In the patient group, cyclopentolate concentrations in aqueous humour were approximately 3000 times higher than those in plasma. Muscarinic cholinoceptors were occupied totally (more than 99.9%) by aqueous humour and 3-18% by plasma taken at 55-125 min. after the drug application. In healthy volunteers peak plasma concentration of cyclopentolate, 2.06+/-0.86 (mean+/-S.D.) nM, occurred at 53 min., maximum receptor occupancy being 5.9+/-2.1%. The maximum pupillary dilatation occured at 30 min. after the drug application. At the same time the near point of vision was extended to more than 50 cm in all subjects. After topical application plasma receptor occupancy was not high enough to cause any significant changes in heart rate and in PQ time. None of the subjects experienced subjectively or objectively adverse effects to be attributed to cyclopentolate.