Mydriatic Effect Research Articles

Pharmacokinetic and pharmacodynamic interactions between almorexant, a dual orexin receptor antagonist, and desipramine

Almorexant is a dual orexin receptor antagonist (DORA) with sleep-enabling effects in humans. Insomnia is often associated with mental health problems, including depression. Hence, potential interactions with antidepressants deserve attention. Desipramine was selected as a model drug because it is mainly metabolized by CYP2D6, which is inhibited by almorexant in vitro. A single-center, randomized, placebo-controlled, two-way crossover study in 20 healthy male subjects was conducted to evaluate the pharmacokinetic and pharmacodynamic interactions between almorexant and desipramine. Almorexant 200mg or matching placebo (double-blind) was administered orally once daily in the morning for 10 days, and a single oral dose of 50mg desipramine (open-label) was administered on Day 5. Almorexant increased the exposure to desipramine 3.7-fold, suggesting that almorexant is a moderate inhibitor of desipramine metabolism through inhibition of CYP2D6. Conversely, desipramine showed no relevant effects on the pharmacokinetics of almorexant. Pharmacodynamic evaluations indicated that almorexant alone reduced visuomotor coordination, postural stability, and alertness, and slightly increased calmness. Desipramine induced a reduction in subjective alertness and an increase in pupil/iris ratio. Despite the increase in exposure to desipramine, almorexant and desipramine in combination showed the same pharmacodynamic profile as almorexant alone, except for prolonging reduced alertness and preventing the miotic effect of almorexant. Co-administration also prolonged the mydriatic effect of desipramine. Overall, repeated administration of almorexant alone or with single-dose desipramine was well tolerated. The lack of a relevant interaction with antidepressants, if confirmed for other DORAs, would be a key feature for a safer class of hypnotics.

Comparative study measuring the dilatory effect of a mydriatic device (Mydriasert(®)) versus topical drops.

To compare the mydriatic efficacy of an ophthalmic insert (Mydriasert, MY) versus phenylephrine and tropicamide (PT) eye drops. Two controlled, prospective, randomized, single-blind studies were performed. In the first study, a total of 80 eyes from 40 outpatient-clinic patients were analyzed. PT drops were applied to the right eye, and a MY device was inserted in the left eye for 30min. Time until maximal pupil dilation for each eye was then assessed. In the second study, 80 eyes from 80 patients undergoing cataract surgery were analyzed. Pupil dilation was achieved using either PT drops three-times for one hour prior to surgery (40 patients), or a MY device was inserted one hour prior to surgery (40 patients). In the first study, MY achieved superior mydriasis compared to PT eye drops at 90min (9.04±1.33mm vs 8.78±1.37mm, P=0.012). However MY took longer than PT drops to achieve maximal dilation, and mydriasis was inferior in eyes with MY compared to PT drops at 30min (7.21±1.73mm vs 8.22±1.43mm, P<0.001), the two groups only becoming similar by 60min (8.85±1.44mm vs 8.71±1.27mm, P=0.236). In the second study, both MY and PT achieved similar levels of mydriasis at the beginning of surgery (8.75±0.76mm with MY vs 8.77±0.63mm with PT), and also at the end of surgery (7.96±1.06mm with MY vs 8.32±0.72mm with PT), with no significant difference between groups (P=0.08). MY was well tolerated and cardiovascular effects were not influenced by dilation method. MY could be a safe and efficacious alternative for mydriasis. The mydriatic effect of MY is as good as conventional PT eye drops after 60min, and is superior after 90min. MY also maintains good pupil dilation during cataract surgery.

Effects of different mydriatics on intraocular pressure, pupil diameter, and ruminal and intestinal motility in healthy sheep

To determine the effects of the administration of subconjunctival 1% atropine (SA), topical 1% atropine (A), 0.5% tropicamide (T), 1% homatropine (H), 10% phenylephrine (P), and 2% ibopamine (I) on intraocular pressure (IOP), pupil diameter (PD), ruminal motility (RM) and intestinal motility (IM) in sheep. Ten spayed ewes of Santa Inês breed. Six experiments were performed separately at 1-week intervals. One eye was randomly selected and received one drop of A, T, H, P, I, or subconjunctival injection of atropine at 8 a.m. On the following days, IOP and PD were evaluated every 8 h until the pupil returned to its normal diameter. Ruminal motility and intestinal motility were evaluated only within the first 13 h. The IOP did not change significantly in the treated eyes compared with the control eyes and baseline at any time point (P > 0.05). A longer-lasting pupil dilation was observed after the administration of A (96 h), SA (79 h), H (24 h), and T (24 h). Within the first 30 min after treatment, RM and IM decreased, by 78% and 82% (H), 76% and 86% (SA), 46% and 58% (A), and 62% and 70% (T) (P < 0.001), respectively, with a tendency to return to baseline values following 13 h of drug administration. Both 10% phenylephrine and 2% ibopamine did not have any effect on the parameters evaluated (P > 0.05). Topical and subconjunctival 1% atropine, 0.5% tropicamide, and 1% homatropine significantly reduced RM and IM, and induced pupil dilation but did not change IOP in eyes of healthy sheep. The sympathomimetics phenylephrine (10%) and ibopamine (2%) did not change the parameters evaluated.

On the Mydriatic Effect of Lidocaine

On the Mydriatic Effect of Lidocaine

Managing Challenges of Recalcitrant Intra-Operative Miosis during Small Incision Cataract Surgery

Reviewed current literature on causes and treatment of recalcitrant intraoperative miosis during small incision cataract surgery (SICS). A Medline, PubMed and Cochrane database internet search was conducted with reference manager 11. Google search was done using key words such as small incision cataract surgery and intraoperative miosis. Some pupils are inherently difficult to either dilate or sustain intraoperative mydriasis, e.g. intraoperative floppy iris syndrome (IFIS). Slow penetration through cornea, limited bioavailability and waning effects of routine topical mydriatics (TMs) are some setbacks that could pose daunting intraoperative challenges. Maintenance of sufficient pupillary dilatation during SICS can be important in successful completion of the operation. A poorly dilating pupil should be identified before surgery so that strategies and equipment are available to the SICS surgeon for the patient.

Posterior chamber injection of intracameral mydriatics increases the durability of the mydriatic response

To compare the mydriatic effect of intracameral mydriatics injected into the anterior or the posterior chamber in routine phacoemulsification cataract surgery. Forty-four patients planned for unilateral phacoemulsification surgery were included after informed consent. Mydriasis was achieved by injecting 150 μl of a mixture of phenylephrine 1.5% and lidocaine 1.0% at the beginning of the procedure. The patients were randomly assigned to injection into the anterior or the posterior chamber. The pupils were filmed during the procedures, and the mean pupil diameters were measured at predetermined intervals from the video recordings by an independent observer. Immediately after the injection, the pupils were larger after posterior chamber injection (3.8 ± 0.8 versus 3.1 ± 0.7 mm; p = 0.004). A similar difference was seen after the phacoemulsification (6.4 ± 0.7 versus 5.9 ± 1.0 mm; p = 0.031). The mydriatic durability was also better after posterior injection (p = 0.004-0.041). Apart from immediately after the injection, the initial mydriatic response was similar with both injection techniques, but the durability of the mydriasis was slightly better after a posterior chamber injection of ICM.

Influence of Mydriatics on Choroidal Thickness Measurement Using Enhanced Depth Imaging-OCT

To evaluate the potential influence of mydriatics on choroidal thickness measurement using enhanced depth imaging optical coherence tomography (EDI-OCT). This was a randomized, double-blind, paired-eye study. Fifty-eight healthy eyes of 29 patients were included in this study, and one eye of each subject was designated randomly as experimental and the contralateral eye as control. A single drop of Mydrin-P (tropicamide and phenylephrine; Santen Pharmaceuticals, Japan) or a single drop of unpreserved saline was administered in the respective eyes of patients three times at 5-min intervals. Choroidal thickness (CT) was measured using EDI-OCT, and changes in CT before and after the administration of the eye drops were analyzed at the subfovea and at 0.5 mm intervals (to 3.0 mm) from the fovea at nasal, temporal, superior, and inferior locations. Linear mixed-model analysis showed no significant changes in subfoveal CT after the administration of eye drops in either the mydriatics [from 313.00 ± 90.05 μm (before) to 316.34 ± 96.91 μm (after), p = 0.500] or placebo group [from 311.07 ± 96.26 μm (before) to 313.14 ± 95.46 μm (after), p = 0.248]. CT did not significantly differ within either group at other measured locations, as we moved further from the subfoveal starting point (all p > 0.05, linear mixed model). In evaluating a possible effect of mydriatics, we detected no significant difference in CT changes between the mydriatic test group and the saline placebo group at all intervals from the fovea (all p > 0.05, linear mixed model). This study demonstrates that mydriatics (Mydrin-P) have no significant influence on clinical measurement of CT, as evaluated by EDI-OCT.

Tropicamide 1% Mydriatic Effect: Comparison Between Spray in Closed Eyes and Eye Drops in Open Eyes

The aim of this study was to evaluate by serial measurements, pupil mydriasis produced by topical application of tropicamide 1% using a spray in a closed eye or instillation in an open eye in adult and elderly populations. The research was done from February to April of 2011 in the Policlinica Ronaldo Gazolla, located in the Arcos da Lapa Campus of Estacio de Sá University, RJ- Brazil. It was a clinical trial, controlled and randomized, made in a series of 50 patients that were being prepared for ophthalmoscopy examination. They were submitted to eye drop administration of 1% tropicamide in an open eye and to eyelid margin vaporization in a closed eye. The eyes were chosen for the administration of drops or spray according to a pseudo-random numbers table from Excel (2007) before application. The pupil diameter was measured before instillation and after 10, 20, and 30 min in both eyes, with a millimeter ruler. Biostat 5.0 software was used for statistical calculations. Tropicamide 1% was vaporized in a group that presented the following average pupil diameters: 3 mm before the application; 4.16 mm in 10 min; 5 mm in 20 min; and 5.35 mm in 30 min. The group in which tropicamide 1% was instilled presented 2.96 mm of average pupil diameter before the application; 4.22 mm at 10 min; 5.02 mm at 20 min; and 5.44 at 30 min. The two way analysis of variance showed P<0.0001, and the Tukey test performed for comparisons among the groups showed statistical significant differences among all groups except when the measurements were done at the same time. The vaporized tropicamide 1% mydriatic effect in closed eyes was clinically equivalent to the instillation effect of eye drop in open eyes. Other mydriatic drugs sprayed in closed eyes may not have the same effect.

Effects of MDMA alone and after pretreatment with reboxetine, duloxetine, clonidine, carvedilol, and doxazosin on pupillary light reflex

Pupillometry can be used to characterize autonomic drug effects. This study was conducted to determine the autonomic effects of 3,4-methylenedioxymethamphetamine (MDMA, ecstasy), administered alone and after pretreatment with reboxetine, duloxetine, clonidine, carvedilol, and doxazosin, on pupillary function. Infrared pupillometry was performed in five placebo-controlled randomized studies. Each study included 16 healthy subjects (eight men, eight women) who received placebo-MDMA (125 mg), placebo-placebo, pretreatment-placebo, or pretreatment-MDMA using a crossover design. MDMA produced mydriasis, prolonged the latency, reduced the response to light, and shortened the recovery time. The impaired reflex response was associated with subjective, cardiostimulant, and hyperthermic drug effects and returned to normal within 6 h after MDMA administration when plasma MDMA levels were still high. Mydriasis was associated with changes in plasma MDMA concentration over time and longer-lasting. Both reboxetine and duloxetine interacted with the effects of MDMA on pupillary function. Clonidine did not significantly reduce the mydriatic effects of MDMA, although it produced miosis when administered alone. Carvedilol and doxazosin did not alter the effects of MDMA on pupillary function. The MDMA-induced prolongation of the latency to and reduction of light-induced miosis indicate indirect central parasympathetic inhibition, and the faster recovery time reflects an increased sympathomimetic action. Both norepinephrine and serotonin mediate the effects of MDMA on pupillary function. Although mydriasis is lasting and mirrors the plasma concentration-time curve of MDMA, the impairment in the reaction to light is associated with the subjective and other autonomic effects of MDMA and exhibits acute tolerance.

Lower conjunctival fornix packing for mydriasis in premature infants: a randomized trial

ObjectiveTo compare the mydriatic effect of lower conjunctival fornix packing to conventional instillation of eyedrops containing 2.5% phenylephrine and 1% tropicamide in premature infants undergoing examination for retinopathy of prematurity.MethodsThe patients were randomized to receive either conventional instillation of mydriatic drops or lower conjunctival fornix packing in one eye and the alternate method in the fellow eye. For the eyes receiving lower conjunctival fornix packing (study group), one small piece of the cotton wool soaked with one drop of 2.5% phenylephrine and one drop of 1% tropicamide was packed in the lower conjunctival fornix for 15 minutes. For the eyes receiving the conventional instillation (control group), 2.5% phenylephrine and 1% tropicamide were alternately instilled every 5 minutes for two doses each. Horizontal pupil diameter was measured with a ruler in millimeters 40 minutes later.ResultsThe mean dilated pupil diameter in study group and control group were 5.76 ± 1.01 mm and 4.50 ± 1.08 mm, respectively. This difference was statistically significant (P < 0.05).ConclusionThe dilated pupil diameter after receiving the lower conjunctival fornix packing was larger than conventional instillation with a statistically significant difference. We recommended the packing method to dilate the preterm infant pupil, especially if the pupil is difficult to dilate.

Efficacy of tropicamide, homatropine, cyclopentolate, atropine and hyoscine as mydriatics in Angora goats

AIM: To document the efficacy of five commercially available mydriatics for their potential for diagnostic and therapeutic use in Angora goats. METHODS: Over 8 weeks, the mydriatic effects of 1% tropicamide, 2% homatropine, 1% cyclopentolate, 1% atropine and 0.25% hyoscine were evaluated. Given as block treatments, drugs were applied randomly to one eye of 10 Angora goats, and the contralateral eye served as a control. Vertical and horizontal pupil diameters were measured to document onset ofeffect, time to reach a difference of 5 mm in the vertical/horizontal pupil diameter between eyes, time to maximum pupillary dilation, and duration of mydriatic action. RESULTS: Onset of mydriasis for all drugs occurred within 15 minutes. Time to reach a difference of 5 mm in the vertical pupil diameter between eyes was shortest for 1% tropicamide and 0.25% hyoscine (0.5 h), then 2% homatropine and 1% atropine (0.75 h), and longest for 1% cyclopentolate (1.5 h). The maximum vertical pupillary dilation occurred earliest with 1% tropicamide and 1% atropine (2 h), followed by 0.25% hyoscine (3 h), 2% homatropine (4 h), and latest with 1% cyclopentolate (8 h). The duration of vertical dilation of the pupil was shortest with 1% tropicamide (6 h), then 2% homatropine (12 h), 1% cyclopentolate (12 h), 1% atropine (24 h), and longest for 0.25% hyoscine (96 h). The time to reach maximum horizontal dilation of the pupil in treated eyes was shortest with 1% cyclopentolate (1 h), followed by 1% tropicamide (1.5 h), 0.25% hyoscine (3 h), 2% homatropine (3.5 h), and 1% atropine (4 h). The duration of horizontal pupil dilation was shortest with 1% tropicamide (4.5 h), and longest with 0.25% hyoscine (48 h). CONCLUSION: All five mydriatics induced clinical dilation. Tropicamide (1%) had the shortest duration of effect, but gave incomplete dilation. Good dilation was achieved with 1% cyclopentolate and 2% homatropine, but took too long to reach maximum dilation for routine mydriasis. The largest vertical dilation of the pupil was achieved with 1% atropine and 0.25% hyoscine, but pupils remained dilated for more than 24 h. CLINICAL RELEVANCE: For routine mydriasis in goats, it is recommended that 1% tropicamide be used, though there may be incomplete dilation. For a longer duration of mydriasis, such as in the treatment of anterior uveitis, 1% atropine or 0.25% hyoscine would be the drugs of choice.

Stimulation of adrenergic β‐receptors enhances mydriasis in a porcine eye model

AbstractPurpose In order to achieve an improved mydriasis in human eyes during cataract surgery, the effect of intracameral phenylephrine was compared to the combination of isoprenaline plus phenylephrine, to epinephrine alone and to a negative control, in a porcine eye model.Methods A total of eighty‐nine eyes from newly slaughtered pigs were acquired and randomly split into four groups. In order to gain miosis all eyes received 2.0 mg of acetylcholine intracamerally, and after 60 seconds the eyes were injected with 0.15 ml 0.3% isoprenaline and 0.15 ml 3.0% phenylephrine sequentially with a 90‐second interval (n=21), the same substances in the reverse order (n=22), 0.15 ml of 0.025% epinephrine (n=20), or 0.15 ml of saline solution (n=26). The diameter of the pupils were measured every 15 seconds, and compared using Student’s t‐test.Results Phenylephrine injected after isoprenaline had a significantly (p&lt;0.01) larger mydriatic effect than epinephrine. The mydriatic effect of phenylephrine, however, was significantly (p&lt;0.05) smaller than that or epinephrine without the isoprenaline pretreatment. Isoprenaline also exhibited a small mydriatic effect of its own.Conclusion This study shows that the β‐receptor has a role in the dilation of the pupil, here demonstrated with the β‐receptor stimulator isoprenaline which augments the mydriatic effect of intracamerally injected phenylephrine. The superior mydriatic effects of a nonspecific adrenergic stimulator such as epinephrine in compare to the specific α1‐receptor stimulator phenylephrine may be explained by this β‐receptor mediated mydriasis.

DIOXATRINE, A POTENT AND SPECIFIC RUMENAL ULCER-PREVENTING AGENT IN RATS.

Abstract When rats are starved with free access to a 20% glucose solution, extensive rumenal ulcers are found in almost all animals at the end of the third week. The formation of these ulcers may be inhibited by dissolving adequate amounts of two anti-acetylcholine agents in the glucose solution. A minimum of about 8 mg/kg of atropine sulphate daily is required for significant activity. Submaximal mydriatic effects are observed after oral administration of this dose. Dioxatrine, a tertiary amine of novel structure, inhibited ulcer formation at dose levels devoid of significant mydriatic activity. Dioxatrine prevents experimental ulcers in rats in one twentieth the dose of atropine.

The central and peripheral activities of anti-acetylcholine drugs. Some concepts of practical relevance.

Abstract Five procedures have been used to compare the pharmacological effects and time-activity profiles of anti-acetylcholine drugs in the central and peripheral nervous system (ens, pns). In particular, the potencies of optically pure enantiomers of anti-acetylcholine drugs which contain an asymmetric centre have been determined. The following four observations are made which are of relevance to all studies of anti-acetylcholine drugs. (1) Times to onset of activity of anti-acetylcholine drugs in three in vivo tests and the duration of action in one in vivo test are shown to increase as affinity constants, determined in vitro, increase. (2) Below a dose of ca 0.03 μmol kg−1no anti-acetylcholine drug produces maximum mydriatic effects and all anti-acetylcholine drugs which have log affinity constant values &amp;gt;9.49 produce maximal effects at approximately this dose. (3) The receptor with which anti-acetylcholine drugs interact is essentially the same in the eye, salivary gland and ens of the mouse, the guinea-pig ileum, and in the cat ens. (4) For any anti-acetylcholine drug the time to onset of effects in the ens is similar to the time of onset of effects in the pns and appears to depend on the affinity constant rather than on the partition properties of the drug. The practical and theoretical significance of these and other observations are discussed.

Stimulation of adrenergic β-receptors enhances mydriasis in a porcine eye model

To compare the mydriatic effect of intracamerally injected isoprenaline plus phenylephrine to phenylephrine alone and to epinephrine in a porcine eye model, aiming to eventually find the best combination of adrenergic substances for surgical mydriasis in humans. In this study, we used 89 intact eyes from newly slaughtered pigs, pretreated with 2.0 mg of intracameral acetylcholine. After waiting 60 seconds for miosis to develop, 0.15 ml 0.3% isoprenaline and 0.15 ml 3.0% phenylephrine were injected sequentially with a 90-second interval in 21 eyes. In another 22 eyes, the same substances were given in the reverse order. In 20 eyes, 0.15 ml of 0.025% epinephrine was injected, and as a negative control 0.15 ml of balanced salt solution was injected in 26 eyes. The pupils were filmed during the treatments, and the mean pupil diameters were measured every 15 seconds from the video recordings. Phenylephrine injected after isoprenaline had a larger mydriatic effect than epinephrine (p < 0.01). Without isoprenaline pretreatment, the mydriatic effect of phenylephrine was significantly smaller than that of epinephrine (p < 0.05). Isoprenaline also exhibited a small mydriatic effect of its own. The β-receptor stimulator isoprenaline enhances the mydriatic effect of intracameral phenylephrine, indicating a role for the β-receptor in the mydriatic response. Mydriasis mediated by β-receptors may explain why nonspecific adrenergic stimulators such as epinine and epinephrine can have larger mydriatic effects than the specific α(1)-receptor stimulator phenylephrine.

A Comparison of Pupil Dilation and Induction of Corneal Endothelial Apoptosis by Intracameral 1% Lidocaine Versus 1:100,000 Epinephrine in Rabbits

The aim of this study was to evaluate the mydriatic effects of intracameral 1% lidocaine compared with 1:100,000 epinephrine and the effect on endothelial apoptosis in rabbits. Forty eyes of 20 New Zealand white rabbits were divided into 2 equal groups. In the first group, 1 eye was injected intracamerally with 1% lidocaine (lidocaine eyes) and the fellow eye with 1:100,000 epinephrine (epinephrine eyes). In the second group, 1 eye was injected with balanced salt solution (BSS eye) and the fellow eye was instilled with 1% tropicamide (mydriatics eye). Specular microscopy, transmission electron microscopy, scanning electron microscopy, and TdT-mediated dUTP nick-end labeling staining were performed 1 day postinjection. Both the full-dilation time and pupil diameters of the lidocaine and epinephrine eyes were not significantly different (P > 0.05). The endothelial cytoplasmic vacuolizations were increased and microprojections were diminished in the epinephrine eyes compared with the mydriatics, BSS, and lidocaine eyes (P < 0.05). Apoptosis was demonstrated in only epinephrine eyes, with an index of 5%. In rabbits, the intracameral injections of preservative-free 1% lidocaine may be used as an adjunctive method with topical mydriatics in cataract surgery, as like 1:100,000 epinephrine. The intracameral 1% lidocaine may induce less microstructural alterations to the corneal endothelial cells than 1:100,000 epinephrine.

Mydriatic effect of topically applied rocuronium bromide in tawny owls (Strix aluco): comparison between two protocols

To evaluate the mydriatic efficacy of a neuromuscular blocking agent (rocuronium bromide) applied topically to only one eye of nocturnal birds of prey and to assess for any general and/or local adverse effects due to its use. Animal studied Twelve healthy adult tawny owls (Strix aluco) were randomly divided in two groups. Six birds (Group 1) received a single dose of 0.35 mg of rocuronium bromide. The second group of subjects (Group 2) received two doses of 0.35 mg of rocuronium bromide (total 0.70 mg/eye). In both groups, the curariform agent was instilled topically. Pupil diameter was measured with a pupillary gauge in 10 min intervals for a total of 100 min and then every 20 min for a total of 240 min. The assessment of the pupillary light reflex was performed using a standard light source during pupillary size recording. Maximal pupillary diameter was 11.5 ± 0.3 mm for Group 1 and 11.0 ± 0.6 mm for Group 2 and no statistically significant differences were detected among the two groups. The maximal pupillary diameter was achieved at T80 for Group 1, and at T60 for Group 2. A complete fundus examination was possible on all treated eyes of subjects of both groups. The drug did not cause any noticeable adverse effects in any of the examined birds. Results of the present study suggest that a single topical administration of 0.35 mg of rocuronium bromide to the eyes of healthy tawny owls results in sufficient mydriasis to allow for a complete examination of the fundus.

Synthesis and pharmacological effects of new,N-substituted soft anticholinergics based on glycopyrrolate

To reduce the possibility of systemic side-effects in locally administered anticholinergics, two new N-substituted glycopyrrolate analogues designed using soft drug design approaches have been synthesized and evaluated in vitro and in vivo. Because stereospecificity is known to be important at muscarinic receptors, the new compounds SGM and SGE also have been prepared as their pure 2R isomers, 2R-SGM and 2R-SGE, by starting from optically pure (-)-cyclopentylmandelic acid, and the corresponding isomers were indeed found to be more active. The new soft glycopyrrolates were chemically more stable under acidic conditions, and the ethyl esters SGE were more stable than the methyl esters SGM. The new compounds were also found to be quite susceptible to extrahepatic metabolism, having half-lives of 20-30 min in rat plasma (in vitro), consistent with their soft nature. Binding studies at human muscarinic receptors (M(1)-M(4)) and guinea-pig ileum assays found 2R-SGM and 2R-SGE to have potencies somewhat less than, but close to, those of glycopyrrolate and N-methylscopolamine. They caused pupil dilation in rabbit eyes, but their mydriatic effects lasted for considerably less time than that of glycopyrrolate, and they did not induce dilation of the pupil in the contralateral, water-treated eyes, indicating that, in agreement with their soft nature, they are locally active, but safe and with a low potential to cause systemic side-effects.

Efficacy of 2% Ibopamine on the Dilation of Patients with Pseudoexfoliation Syndrome

To compare the mydriatic effects of 2% ibopamine and collyrium containing 10% phenylephrine + 0.5% tropicamide and to study the associated drug in patients with ocular pseudoexfoliation (PEX) syndrome. This was a prospective, comparative, interventional clinical study. The study group consisted of 20 patients with ocular PEX syndrome. Intervention procedures included administration of 10% phenylephrine-0.5% tropicamide versus 2% ibopamine versus 2% ibopamine followed by the combination drug. Main outcome measurement was mydriatic efficacy measured in terms of mean pupil diameter. Adverse effects on intraocular pressure (IOP) were measured with a Goldmann applanation tonometer. Mean premedication pupil diameters in all patients were less than 3.5 mm. Instillation of 10% phenylephrine-0.5% tropicamide caused significantly greater mydriasis than 2% ibopamine (pupil diameters: 6.17 mm, SD=1.14 versus 5.33 mm, SD=1.34; p<0.001). Combined use of both collyria significantly increased mydriasis (7.19 mm; SD=0.69) compared with that induced by either of the products alone (p<0.001). Inadequate mydriasis (pupil diameters < 5.5 mm) was observed in 2 patients after administration of 10% phenylephrine-0.5% tropicamide and in 10 following instillation of 2% ibopamine, but the addition of 10% phenylephrine -0.5% tropicamide to ibopamine-treated eyes resulted in adequate dilation in all cases. IOP increases of 4 mmHg over baseline values were observed in 12 (60%) patients after 2% ibopamine. In patients with ocular PEX, instillation of 2% ibopamine exerts a significant additive effect on mydriasis induced with 10% phenylephrine-0.5% tropicamide with only minimal increases in IOP.

Evaluation of the mydriatic effect of intracameral lidocaine hydrochloride injection in eyes of clinically normal dogs

OBJECTIVE-To evaluate the mydriatic effect of intracameral injection of preservative-free 1% and 2% lidocaine hydrochloride solutions and determine the onset and duration of mydriasis according to the concentration and volume of lidocaine administered in healthy dogs. ANIMALS-5 healthy adult Beagles weighing 7 to 10 kg, with no apparent ocular disease. PROCEDURES-A double-blind randomized 9-session crossover trial was designed. Both eyes were assigned to 9 treatments with a minimum 7-day washout period between treatments: 0.1, 0.2, and 0.3 mL of 2% lidocaine solution; 0.1, 0.2, and 0.3 mL of 1% lidocaine solution; and 0.1, 0.2, and 0.3 mL of balanced salt solution. Dogs were anesthetized, and the allocated treatment was injected intracamerally after aspiration of the same volume of aqueous humor from the anterior chamber of each eye. Two perpendicular pupil diameters were measured. Intraocular pressure, heart rate, respiratory rate, ECG readings, and end-tidal partial pressure of CO(2) were monitored. RESULTS-Intracameral injection of 1% or 2% lidocaine solutions in volumes of 0.1 to 0.3 mL induced a significant degree of mydriasis, and the effect was maintained for 74 to 142 minutes. Lidocaine injection had no significant effect on intraocular pressure, heart rate, respiratory rate, ECG readings, or end-tidal partial pressure of CO(2). CONCLUSIONS AND CLINICAL RELEVANCE-Intracameral lidocaine injection in healthy dogs induced mydriasis, the timing of which was affected by concentration and volume of lidocaine. This technique could serve as an alternative to topically administered mydriatics for intraocular surgery in dogs.