The use of topical nalbuphine in different concentrations to control pain after photorefractive keratectomy

PURPOSE

This is a randomized controlled study aiming to evaluate the safety and efficacy of two different concentrations of topical nalbuphine hydrochloride, when used to relieve pain in the first days following photorefractive keratectomy (PRK).

METHODS

This is a prospective double blinded randomized clinical trial that included 189 patients who had PRK for correction of low and moderate refractive errors. Patients were randomly assigned to three groups according to the eye drops given to relieve pain in the first three postoperative days; the first group received topical nalbuphine with a concentration of 2 mg/ml (Group A = 64 patients), the second group received topical nalbuphine in a concentration of 1 mg/ml (Group B = 69 patients) and the third group received topical artificial tears only (Group C = 56 patients).The patients were asked to rate their pain daily using a numeric rating scale and to record the number of drops instillation times/day. The time needed for complete epithelial healing, best-corrected visual acuity (BCVA) and spherical equivalent after three months were recorded in each group.

RESULTS

In the first three days, there was a statistically significant difference in pain score among the three groups with lower values in the two topical nalbuphine groups when compared with the control group receiving artificial tears. Moreover, the higher concentration group showed significantly lower pain score and less number of drops used /day in comparison with the lower concentration group.There were no statistically significant differences in epithelial healing time, BCVA and spherical equivalent after three months among the three groups.

CONCLUSION

The use of topical nalbuphine is effective in relieving pain in the first few days following PRK and this pain relief is not associated with any compromise regarding epithelial healing nor refractive outcome. The pain control with 2 mg/ml concentration is significantly higher than that with 1 mg/ml concentration of nalbuphine. Trial registration numberISRCTN21394752 https://doi.org/10.1186/ISRCTN21394752 The trial is retrospectively registered in ISRCTN registry at March 08, 2021.

Evaluation of corneal anaesthesia after the application of topical 0.5% bupivacaine, 2% lidocaine and 0.4% oxybuprocaine in normal horses

OBJECTIVE

To compare the corneal anaesthetic effect of 0.5% bupivacaine, 2% lidocaine and 0.4% oxybuprocaine on normal equine eyes.

STUDY DESIGN

Prospective, blinded crossover study.

ANIMALS

A group of 10 clinically healthy horses.

METHODS

Corneal sensitivity was determined in each eye by measuring corneal touch threshold (CTT). The study had three phases. Each subject was randomly given one of the three treatments followed by a 72 hour washout period. Every horse received all treatments. Baseline CTT was recorded prior to anaesthetic instillation (T0) then CTT was measured 5 and 10 minutes after (T1 and T2, respectively), then 20 to 90 minutes (T3 to T10) at 10 minute intervals. CTT data were compared among treatments at each time point using the Friedman test p < 0.05.

RESULTS

Median (range) baseline CTT was 51.3 (25.0-60.0) mm for bupivacaine, 50.0 (40.0-55.0) mm for oxybuprocaine and 55.0 (30.0-60.0) mm for lidocaine. All treatments caused a significant decrease in CTT at T1. The lowest CTT was observed at T3 with bupivacaine and oxybuprocaine treatments. Median CTTs at this time point were 18.7 (5.0-25.0) mm and 28.7 (25.0-40.0) mm, respectively. The lowest CTT with lidocaine treatment was 28.7 (20.0-50.0) mm at T6 (50 minutes). At T3, CTT was significantly lower with the bupivacaine treatment compared with oxybuprocaine and lidocaine treatments (p < 0.0074). There was no significant difference in CTT values between T1 and T6 for bupivacaine, between T1 and T7 for lidocaine, and between T1 and T8 for oxybuprocaine. Duration of the maximum effect was 45 minutes for the bupivacaine, 55 minutes for the lidocaine and 65 minutes for the oxybuprocaine treatment.

CONCLUSIONS AND CLINICAL RELEVANCE

Administration of a 0.5% injectable solution of bupivacaine or a 2% lidocaine had similar anaesthetic effect to the commonly used oxybuprocaine. Therefore, they might be used as alternatives for corneal anaesthesia.

Retrobulbar lidocaine injection via the supraorbital fossa is safe in adult horses but produces regionally variable periocular anaesthesia

BACKGROUND

Injection techniques for retrobulbar anaesthesia are published in horses, but neither safety nor anaesthetic efficacy and duration have been evaluated objectively in vivo.

OBJECTIVE

To characterise the safety and efficacy of one published technique for retrobulbar anaesthesia.

STUDY DESIGN

Randomised, controlled descriptive experiment.

METHODS

Unilateral retrobulbar injection with 10 mL lidocaine (2%) was performed in eight sedated adult mares. Contralateral eyes served as untreated controls. Neurophthalmic parameters, intraocular pressure (IOP), and corneal and periocular sensation were measured awake, post-sedation and at periodic time points for 24 hours following injection. Adverse effects were documented.

RESULTS

Injection of 10 mL lidocaine significantly increased IOP for up to 2 hours (P < .05) maximally at 30 min (mean [95% CI]: 6.0 [2.7, 9.2] mm Hg, P < .001). Six of the eight treated eyes developed mild to moderate reversible chemosis for 2 to 24 hours. One eye developed severe chemosis and superficial corneal ulceration at 24 and 48 hours following injection respectively. Corneal sensitivity significantly decreased for 6 hours (P < .05), maximally at 10 min (-44.4 [-34.6, -54.1] mm, P < .001). Periocular sensitivity (measured as increase in applied force) significantly decreased dorsally and medially for up to 2 hours (maximal at 2 hours (367.1 [238.5, 495.7] g, P < .001, and at 30 min: 345.8 [202.6, 488.9] g, P < .001) respectively). Ventral and lateral sensitivity were not effectively decreased beyond 30 min. Optic nerve function was not consistently reduced following injection.

MAIN LIMITATIONS

Investigators were not masked to the treated eye.

CONCLUSIONS

Retrobulbar injection using 10 mL lidocaine is safe in normal eyes of adult horses, but carries risk in structurally compromised or glaucomatous eyes due to transient IOP increase. Reversible chemosis commonly develops 2-4h following injection, and may be severe in some horses with risk for corneal ulceration. Corneal anaesthesia is rapid and prolonged, but all periocular regions are not consistently anaesthetised. Retrobulbar injection should be combined with other local anaesthetic injections for eyelid surgeries or enucleations.

Analgesic effect of topical and subconjunctival morphine in dogs after phacoemulsification: A pilot study

OBJECTIVE

To determine the efficacy of a single treatment of topical and subconjunctival 0.1% preservative-free morphine sulfate (PFMS) in providing analgesia following phacoemulsification in dogs.

ANIMALS STUDIED

Ten diabetic and ten non-diabetic client-owned dogs treated with bilateral phacoemulsification.

PROCEDURES

A prospective, randomized, masked, negative-controlled clinical trial was performed. All dogs received topical (0.2 mL) and subconjunctival (0.1 mL) 0.1% PFMS in one eye following phacoemulsification. The other eye received an equal volume and mode of administration of balanced salt solution (BSS). Ophthalmic examination, blinking rates, tearing, conjunctival hyperemia, aqueous flare, and central corneal esthesiometry (CCE) were evaluated in all eyes 1 day prior to surgery and at 4, 24, and 48 hours after surgery. Complete physical examination, ocular ultrasound, electroretinogram, hemogram, and serum biochemistry panel were performed in all dogs prior to phacoemulsification. All dogs received the standard of care treatment before and after surgery, including uniform anesthetic protocol.

RESULTS

Baseline ophthalmic exams were unremarkable, except for the presence of cataracts, in all dogs. The mean CCE (±SD) at 4 hours post-operatively was 1.76 ± 1.27 g/mm² and 1.85 ± 1.5 g/mm² for the negative control and PFMS groups, respectively. There were no statistical differences in blepharospasm, conjunctival hyperemia, tearing, aqueous flare, blinking rates, CCE, or intraocular pressure (IOP) between the treatment groups for any of the time points for the non-diabetic and diabetic dogs, or for all dogs combined (P > .05).

CONCLUSIONS

Topical and subconjunctival 0.1% PFMS did not affect the evaluated parameters after phacoemulsification in the study dogs at the timepoints assessed.

Pharmacokinetic evaluation and safety of topical 1% morphine sulfate application on the healthy equine eye

OBJECTIVE

To determine if corneal epithelial cell integrity is detrimentally affected by short-term administration of 1.0% morphine sulfate. Additionally, we sought to determine if topical 1.0% morphine applied to the equine cornea would result in ocular or systemic absorption.

ANIMAL STUDIED

Six healthy horses.

PROCEDURE

Morphine sulfate (1.0%) was applied topically to one eye every four hours for 72 h before horses were euthanized. Serum samples were collected at varying time points during the study and aqueous and vitreous humor were collected immediately after euthanasia. Morphine quantification in serum, aqueous, and vitreous humor was performed by ELISA. Treated and control corneas were submitted for histopathology. Horses were monitored for adverse ocular and systemic effects throughout the study period.

RESULTS

All horses developed mild mucoid ocular discharge in the treated eye. One horse developed a fever during treatment. Morphine was detected in the aqueous humor of the treated eye for all horses with mean ± standard deviation of 165.18 ng/mL ± 87.69 ng/mL. Morphine was detected in vitreous humor of the treated eye of 5 of 6 horses with mean ± standard deviation of 4.87 ± 4.46 ng/mL. Morphine was detected in the serum of 5 of 6 horses at varying time points. Maximum systemic concentration reached in a single horse was 6.98 ng/mL. Corneal histopathology revealed no difference in microscopic appearance between morphine-treated and control corneas.

CONCLUSIONS

Topical administration of 1.0% morphine sulfate did not appear to cause any significant ocular or systemic adverse effects. Topical ophthalmic morphine application resulted in both ocular and systemic absorption.

Effects of 0.2% brimonidine and 0.2% brimonidine-0.5% timolol on intraocular pressure and pupil size in normal equine eyes

BACKGROUND

Brimonidine is an α₂ -adrenergic agonist that decreases aqueous humour production and may increase uveoscleral outflow. It has not been evaluated in normal or glaucomatous equine eyes.

OBJECTIVES

To evaluate the efficacy and safety of brimonidine in lowering intraocular pressure (IOP), alone and in conjunction with timolol, as a treatment for equine glaucoma by comparing IOP in normal equine eyes treated with brimonidine and brimonidine-timolol, respectively, with IOP in control eyes.

STUDY DESIGN

A balanced crossover design with 16 horses receiving one of two treatments, brimonidine and brimonidine-timolol, during each of two 10-day study phases, was used. Four horses were randomly assigned to each of four combinations of treated eye (right or left) and drug order within the two 10-day study phases (brimonidine first or brimonidine-timolol first).

METHODS

Pupil size and conjunctival hyperaemia were assessed twice per day and IOP was measured three times per day using rebound tonometry in both eyes of 16 normal horses throughout two 10-day study periods (brimonidine and brimonidine-timolol) separated by an 18-day washout period. One eye of each horse was treated with brimonidine or brimonidine-timolol and the opposite eye was treated with balanced salt solution (BSS).

RESULTS

There were no adverse effects and no significant changes in pupil size in normal equine eyes treated with brimonidine or brimonidine-timolol. Average IOP in normal equine eyes treated with brimonidine (25.6 mmHg) was statistically higher than in eyes treated with brimonidine-timolol (24.6 mmHg) or BSS (24.5 mmHg). However, IOP differences were of ≤1 mmHg and thus not clinically important.

MAIN LIMITATIONS

Horses with normal eyes may not be as sensitive to the IOP-lowering effects of treatment as horses with glaucoma.

CONCLUSIONS

Brimonidine and brimonidine-timolol are well tolerated in normal horses but do not decrease IOP.

Degree of corneal anaesthesia after topical application of 0.4% oxybuprocaine hydrochloride and 0.5% proparacaine hydrochloride ophthalmic solution in clinically normal cattle

OBJECTIVES

The use of corneal anaesthesia is necessary for a range of clinical purposes. Therefore, we assessed and compared the efficacy of corneal anaesthesia after application of 0.4% oxybuprocaine hydrochloride and 0.5% proparacaine hydrochloride ophthalmic solution in clinically normal cattle.

METHODS

The 24 clinically normal cows were allocated into two groups. Cows in group 1 (n = 12) received 0.2 mL of 0.4% oxybuprocaine hydrochloride with fluorescein ophthalmic solution in one eye and 0.2 mL of sterile saline (0.9% NaCl) with fluorescein in the contralateral eye (control). Group 2 (n = 12) received 0.2 mL of 0.4% oxybuprocaine hydrochloride with fluorescein ophthalmic solution in one eye and 0.2 mL of 0.5% proparacaine hydrochloride with fluorescein in the contralateral eye (control). In each group, corneal touch threshold was determined by Cochet-Bonnet aesthesiometer for both eyes immediately prior to topical administration of solutions, at 1 min and 5 min after administration of topical solutions and every 5 min thereafter for a total of 75 min.

RESULTS

Significant corneal anaesthesia was noted immediately following topical application of both oxybuprocaine and proparacaine as compared with controls, with maximal corneal anaesthesia noted 1 min after administration. Both oxybuprocaine and proparacaine produced significant corneal anaesthesia for the duration of the 75-min study. Neither oxybuprocaine hydrochloride nor proparacaine hydrochloride treatment resulted in visible adverse effects.

CONCLUSION

There are limited data available demonstrating the efficacy and duration of corneal anaesthetic agents in cattle. Both oxybuprocaine hydrochloride and proparacaine hydrochloride should be considered practical options for providing corneal anaesthesia in cattle in a clinical setting.

Degree and duration of corneal anesthesia after topical application of 0.4% oxybuprocaine hydrochloride ophthalmic solution in ophthalmically normal dogs

OBJECTIVE

To assess the anesthetic efficacy and local tolerance of topically applied 0.4% oxybuprocaine ophthalmic solution to in dogs and compare its effects with those of 1% tetracaine solution.

ANIMALS

34 ophthalmically normal Beagles.

PROCEDURES

Dogs were assigned to 2 groups, and baseline corneal touch threshold (CTT) was measured bilaterally with a Cochet-Bonnet aesthesiometer. Dogs of group 1 (n = 22) received a single drop of 0.4% oxybuprocaine ophthalmic solution in one eye and saline (0.9% NaCl) solution (control treatment) in the contralateral eye. Dogs of group 2 (n = 12) received a single drop of 0.4% oxybuprocaine ophthalmic solution in one eye and 1% tetracaine ophthalmic solution in the contralateral eye. The CTT of each eye was measured 1 and 5 minutes after topical application and then at 5-minute intervals until 75 minutes after topical application.

RESULTS

CTT changes over time differed significantly between oxybuprocaine-treated and control eyes. After instillation of oxybuprocaine, maximal corneal anesthesia (CTT = 0) was achieved within 1 minute, and CTT was significantly decreased from 1 to 45 minutes, compared with the baseline value. No significant difference in onset, depth, and duration of corneal anesthesia was found between oxybuprocaine-treated and tetracaine-treated eyes. Conjunctival hyperemia and chemosis were detected more frequently in tetracaine-treated eyes than in oxybuprocaine-treated eyes.

CONCLUSIONS AND CLINICAL RELEVANCE

Topical application of oxybuprocaine and tetracaine similarly reduced corneal sensitivity in dogs, but oxybuprocaine was less irritating to the conjunctiva than was tetracaine.

Analysis of the transport of and cytotoxic effects for nalbuphine solution in corneal cells

OBJECTIVE

To assess the in vitro effects of various nalbuphine concentrations on viability and wound healing ability of corneal cells and potential drug transport through the corneal epithelium.

SAMPLE

Cultured canine and human corneal epithelial cells (CECs) and cultured canine corneal stromal fibroblasts.

PROCEDURES

CECs and stromal fibroblasts were exposed to nalbuphine (concentration of solutions ranged from 0% to 1.2%) for up to 30 minutes, and viability was assessed with a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. A standard scratch test technique was used. Wound healing of CECs and stromal fibroblasts was evaluated following treatment with nalbuphine solutions < 0.1%. Liquid chromatography-mass spectrometry-mass spectrometry analysis was used to evaluate drug transport across a monolayer and a multilayer of human CECs.

RESULTS

A progressive decrease in viability was detected in canine CECs for all nalbuphine treatment groups, whereas treatment with only 0.5% or 1.2% nalbuphine significantly reduced corneal stromal fibroblast viability, compared with results for control cells. Within 24 hours, treatment with 0.1% nalbuphine solution significantly altered the healing rate of both canine CECs and stromal fibroblasts. Continuous increases in transport rates of nalbuphine were detected with time for both the monolayer and multilayer of human CECs.

CONCLUSIONS AND CLINICAL RELEVANCE

In vitro, nalbuphine potentially could penetrate through corneal tissue, but it may cause damage to the corneal epithelium and stromal fibroblasts. Therefore, nalbuphine potentially may impair corneal wound healing.

Effect of topical administration of 0.8% nalbuphine on the cornea in dogs after phacoemulsification

It is suggested that topical application of opioids may provide localized analgesia without delay in corneal wound healing. This study was designed to evaluate the effect of topical application of 0.8% nalbuphine on post-operative ocular pain in dogs. Twelve eyes from 11 dogs undergoing phacoemulsification cataract surgery were divided into a nalbuphine group (n=6) and saline group (n=6). Postoperatively, the nalbuphine group received 0.1 ml of topical 0.8% alkalinized nalbuphine (pH 5.6) every 8 hr, and the saline group received 0.1 ml of topical saline (pH 5.9) as a placebo. All dogs received systemic postoperative pain managements with oral tramadol (4 mg/kg) and prednisolone (0.5 mg/kg) every 8 hr. All dogs received pre- and post-ophthalmic examinations. Pain was scored in the dogs using a pain scoring system modified from the University of Melbourne pain scale at 15, 30 and 60 min following the topical treatment on days 1 and 2 (24 and 48 hr after surgery). Eye blink frequency and corneal touch threshold (CTT) were recorded at the same time. There was no statistical difference in the pain score between groups. Significant decreases in CTT, blepharospasm and eye blink frequency were observed after the topical nalbuphine treatment. This indicated that topical application of 0.8% nalbuphine solution can produce a rapid reduction of corneal discomfort in dogs.