Effect of topical application of 0.5% proparacaine on corneal culture results from 33 dogs, 12 cats, and 19 horses with spontaneously arising ulcerative keratitis.

OBJECTIVE: To investigate the effect of topically applied proparacaine on bacterial and fungal culture results and to compare cytologic and culture results in patients with ulcerative keratitis. PROCEDURE: Corneal samples were collected from 33 dogs, 19 horses, and 12 cats with spontaneously arising ulcerative keratitis. Samples for bacterial (dogs, cats, horses) and fungal (horses) cultures were collected prior to and following application of 0.5% proparacaine or saline. All patients then received a topical anesthetic, and samples were collected for cytology. Frequency of cultivatable bacteria before (Swab 1) and after (Swab 2) application of proparacaine or saline was compared using Fisher's exact test. Homogeneity of culture and cytology results was assessed using McNemar's test. RESULTS: No difference was detected in number of animals from which bacteria were isolated from Swab 1 or Swab 2 for proparacaine (21/37 and 17/37, respectively) or saline (10/27 and 12/27, respectively). Small numbers prevented analysis of fungal culture results in horses between Swab 1 and Swab 2 for proparacaine (2/12 and 1/12, respectively) or saline (both, 1/8). Bacteria were isolated from 10 of 20 horses and detected cytologically in 3 of these; fungi were isolated from 3 of 20 horses and detected cytologically in 2 of these. Bacteria were detected more frequently using culture (31/64) than cytology (19/64). CONCLUSION: Proparacaine did not significantly alter bacterial or fungal culture results in cats, dogs, or horses; however, clinical significance warrants investigation. Culture and cytology provided complementary data; both should be performed to maximize organism detection in patients with ulcerative keratitis.

Comparison of Proparacaine, Tetracaine, and Oxybuprocaine in Corneal Sensitivity Measurement.

Purpose: This study aimed to determine the onset and duration of action of 3 commercially available topical anesthetic solutions in Brazil, using the Cochet-Bonnet esthesiometer (Luneau®, Paris, France) and to quantitatively assess patient-reported discomfort during application. Methods: A prospective, randomized, masked, and double-blind study was conducted, involving 40 eyes from 21 patients. Patients were administered each one of the topical anesthetics weekly, and corneal sensitivity was measured using the Cochet-Bonnet esthesiometer's corneal touch threshold (CTT). Patients rated the burning sensation using a visual analogue scale (VAS). Results: Among the 21 patients (42.9% male), with a mean age of 31.95 years (±standard deviation = 10.17, range = 22.0-58.0), corneal sensitivity significantly decreased 30 s after application, returning to baseline after 30 min for all groups (P < 0.0001). Significant differences in CTT were observed at 5 min, with proparacaine exhibiting a superior anesthetic effect (P = 0.0003), at 10 min, where tetracaine displayed the most substantial anesthetic effect (P = 0.0135), and at 20 min, where tetracaine demonstrated the highest anesthetic efficacy (P < 0.0001). VAS scores indicated the most intense burning sensation with tetracaine (P < 0.0001). Men reported experiencing more discomfort during instillation compared with women (P = 0.0168). Conclusions: Proparacaine exhibited the fastest onset of action among the 3 topical anesthetics and provided a more comfortable eye sensation during instillation. However, tetracaine demonstrated the longest duration of action despite causing more discomfort.

Effect of topical anesthesia on evaluation of corneal sensitivity and intraocular pressure in rats and dogs.

OBJECTIVE: To determine the effect of 0.5% proparacaine in tonometry by evaluating corneal touch threshold (CTT) and intraocular pressure (IOP). ANIMAL STUDIED: Nine rats (18 eyes, Sprague-Dawley) and 10 dogs (20 eyes, Beagle) PROCEDURES: The IOP and CTT were measured in each eye before and after topical anesthesia with 0.5% proparacaine. The IOP was evaluated using Tonopen for dogs and Tonolab for rats. The corneal sensitivity was evaluated by CTT through a Cochet-Bonnet aesthesiometer. RESULTS: The mean IOP was not significantly changed in rats or dogs before and after topical anesthesia. However, after application of proparacaine, CTT was significantly increased in both animal groups compared with that before application of proparacaine. CONCLUSION: From this study, topical anesthesia was found to significantly lower the corneal sensitivity but have little effect on IOP measurements. In ophthalmologic examination, topical anesthesia can be used to reduce corneal sensation without an effect on IOP.

The in vitro effects of proxymetacaine, fluorescein, and fusidic acid on real-time PCR assays used for the diagnosis of Feline herpesvirus 1 and Chlamydophila felis infections.

PURPOSE: To investigate the possible inhibition of qPCR assays used for the diagnosis of ocular infections in cats by proxymetacaine, fluorescein, and fusidic acid, which are commonly used in veterinary ophthalmology. METHODS: Fluorescein, proxymetacaine, and fusidic acid were tested for possible inhibition of a triplex qPCR assay designed to detect Chlamydophila felis, Feline herpesvirus 1 (FHV-1), and the feline 28S ribosomal DNA (28S rDNA) gene by comparing threshold cycle (C(t) ) values of samples with and without the three products. A second experiment was carried out to measure the effects of various dilutions of fusidic acid. RESULTS: No statistically significant differences were detected between the C. felis, FHV-1, and 28S rDNA C(t) values with and without proxymetacaine or fluorescein. However, there was a statistically significant increase in FHV-1 (P < 0.01), C. felis (P < 0.01), and 28S rDNA (P < 0.05) C(t) values when fusidic acid was used. When dilutions of fusidic acid were tested, the results revealed that only the 1:2 dilution caused a statistically significant increase (P < 0.01) in the FHV-1 Ct values. CONCLUSION: Proxymetacaine and fluorescein did not interfere with our qPCR assays for the detection of C. felis and FHV-1. The presence of fusidic acid caused a small inhibitory effect of doubtful clinical significance. In vivo studies are required to establish the clinical relevance of this study and to confirm our findings.

Assessing the Clinical Requirement of 2.5% Phenylephrine for Diagnostic Pupil Examination.

Purpose: To evaluate whether the standard dilating drop regimen consisting of phenylephrine, tropicamide, and proparacaine produces clinically significant improvement in pupil size compared to tropicamide and proparacaine during diagnostic eye examination. Methods: Sixty-three adult patients at Washington University School of Medicine Eye Clinic were enrolled in this prospective, randomized trial. Each patient received one of two dilating drop regimens: phenylephrine + tropicamide + proparacaine (PE+T+PP), which is considered the standard therapy, or tropicamide + proparacaine (T+PP). Main outcome measures were the proportion of pupils able to achieve successful clinical examination without need for additional dilating drops and change in predilation to postdilation pupil size. Comparisons were made using McNemar's test, repeated measures analysis of variance, and Fisher's test to determine whether PE is a necessary component of the standard eye examination. Results: There were no statistically significant differences between the PE+T+PP and T+PE treatment groups in predilation to postdilation changes in average resting pupil size (1.58 ± 0.66 and 2.61 ± 0.79; P = 0.57) or constricted pupil size (2.52 ± 0.93 and 3.56 ± 0.96; P = 0.15). There was no statistically significant difference between patients who obtained a successful dilated pupil examination between those receiving PE+T+PP and those receiving T+PP as determined by the examining physicians (Fisher's, P = 0.67). Conclusion: The addition of phenylephrine to tropicamide and proparacaine did not improve pupillary dilation size or ability to conduct a clinical examination. A single dilating agent using tropicamide should be considered in clinical practice.

The effect of propoxycaine.HCl on the physical properties of neuronal membranes.

Fluorescent probe techniques were used to evaluate the effect of propoxycaine.HCl on the physical properties (transbilayer asymmetric lateral and rotational mobilities, annular lipid fluidity and protein distribution) of synaptosomal plasma membrane vesicles (SPMVs) isolated from bovine cerebral cortex. An experimental procedure was used based on selective quenching of both 1,3-di(1-pyrenyl)propane (Py-3-Py) and 1,6-diphenyl-1,3,5-hexatriene (DPH) by trinitrophenyl groups, and radiationless energy transfer (RET) from the tryptophans of membrane proteins to Py-3-Py. Propoxycaine.HCl increased the bulk lateral and rotational mobilities, and annular lipid fluidity in SPMVs lipid bilayers, and had a greater fluidizing effect on the inner monolayer than that of the outer monolayer. The magnitude of increasing effect on annular lipid fluidity in SPMVs lipid bilayer induced by propoxycaine.HCl was significantly far greater than magnitude of increasing effect of the drug on the lateral and rotational mobilities of SPMVs lipid bilayer. It also caused membrane proteins to cluster. These effects of propoxycaine.HCl on neuronal membranes may be responsible for some, though not all, of the local anesthetic actions of propoxycaine.HCl.

Evaluation of duration of corneal anesthesia induced with ophthalmic 0.5% proparacaine hydrochloride by use of a Cochet-Bonnet aesthesiometer in clinically normal horses.

OBJECTIVE: To measure duration of corneal anesthesia and time and degree of maximal anesthetic effect of 0.5% proparacaine hydrochloride by use of a Cochet-Bonnet aesthesiometer in horses. ANIMALS: 10 clinically normal adult horses. PROCEDURES: Baseline corneal touch threshold (CTT) was measured in millimeters for 1 randomly selected eye of each horse by use of the aesthesiometer by applying the filament to the cornea at maximum length (60 mm) and decreasing in 5-mm increments until a consistent blink response was elicited. Following baseline CTT measurement, 0.2 mL of 0.5% proparacaine hydrochloride was instilled in the selected eye. The CTT was measured within 1 minute following proparacaine administration and every 5 minutes thereafter for 60 minutes. A mixed-model ANOVA with tested eye varying between subjects and measurement time varying within subject was used to test for main effects and any interaction between these factors. A contrast between means of baseline and each subsequent CTT identified the duration of corneal anesthesia as the time at which there was no difference from baseline. Maximal anesthetic effect occurred at the time with the lowest mean CTT. RESULTS: Duration of corneal anesthesia achieved by use of proparacaine was 25 minutes, and maximal anesthetic effect occurred within 5 minutes, although CTT never went to 0 in any horse at any time. CONCLUSIONS AND CLINICAL RELEVANCE: Duration of corneal anesthesia in horses was shorter than in dogs, and degree of maximal effect was less than in cats and dogs, most likely because of increased sensitivity of the equine cornea, compared with corneal sensitivity in those species.

Proparacaine-Induced Mydriasis During Strabismus Surgery.

AIM: To evaluate the mydriatic effect of proparacaine hydrochloride (PH) in children undergoing strabismus surgery under general anesthesia (GA). METHODS: This was a pilot, prospective, non-randomized, self-controlled interventional study. Nine children with esotropia or exotropia undergoing horizontal muscle squint surgery under GA at a tertiary eye care center were included. The six Group 1 patients underwent both eye surgeries, while the three Group 2 patients underwent single eye surgery. PH was instilled in one eye of Group 1 patients and both eyes of Group 2 patients. Change in pupil diameter (PD) was analyzed as the main outcome measure. RESULTS: Mean age of the patients was 4.67 ± 2.64 years. In the study eyes, mean average baseline PD was 1.59 ± 0.40 mm (range: 1.06-2.37), while postoperative average PD was 3.99 ± 1.34 mm (range: 1.79-6.02). The mean baseline PC had increased from 5.51 ± 1.09 mm to 12.6 ± 3.58 mm at the end of the surgery. PD and PC increased in all of the study eyes while no change in PD or PC was seen in the control eyes of either of the groups. The dilated pupil was skewed horizontally towards the muscle being operated upon in all of the study eyes. CONCLUSIONS: PH has a mydriatic effect of its own. It penetrates through the bare sclera and leads on to skewed dilation of the pupil. Surgeons should consider this effect while judging pupil alignment at the end of the surgery.

Effects of topical ophthalmic application of 0.5% proparacaine hydrochloride on aerobic bacterial culture results for naturally occurring infected corneal ulcers in dogs.

OBJECTIVE To evaluate the effects of topical ophthalmic application of 0.5% proparacaine hydrochloride solution (PHCL; containing 0.01% benzalkonium chloride as preservative) on aerobic bacterial culture results for naturally occurring infected corneal ulcers in dogs. DESIGN Clinical trial. ANIMALS 25 client-owned dogs with infected corneal ulcers (24 unilaterally affected and 1 bilaterally affected; only 1 eye included/dog) examined between June 2008 and May 2011. PROCEDURES Swab samples for aerobic bacterial culture were collected from the periphery of each corneal ulcer before and approximately 1 minute after topical ophthalmic application of 1 drop of PHCL. Numbers of aerobic bacterial species isolated from affected eyes were compared between sample collection points and between other variables (ie, side [left or right] of affected eye, prior treatments, and patient age, sex, and neuter status). RESULTS There was no significant difference between numbers of aerobic bacterial species isolated per eye or overall aerobic bacterial culture results (positive or negative) before versus after PHCL application. Similarly, prior treatment had no significant effect on aerobic bacterial culture results for samples collected at either point. The most commonly isolated bacteria before and after PHCL application were Staphylococcus spp (40% and 48%, respectively), followed by Streptococcus spp (23% and 22%, respectively). CONCLUSIONS AND CLINICAL RELEVANCE Topical ophthalmic application of PHCL did not significantly affect aerobic bacterial culture results for naturally occurring infected corneal ulcers in dogs as assessed in this study. Therefore, topical ophthalmic PHCL application could be useful in clinical settings prior to sample collection to relieve patient discomfort and to aid in sample acquisition without compromising aerobic bacterial culture results.

Duration of corneal anesthesia following topical administration of 0.5% proparacaine hydrochloride solution in clinically normal cats.

OBJECTIVE: To determine duration of corneal anesthesia following topical administration of 0.5% proparacaine hydrochloride solution in domestic shorthair (DSH) cats. ANIMALS: 20 clinically normal DSH cats. PROCEDURES: Baseline corneal touch threshold (CCT) was established by use of a Cochet-Bonnet aesthesiometer. Treatment consisted of a single 50-microL topical application of an ophthalmic preparation of 0.5% proparacaine solution to a randomly selected eye of each cat. The corneal touch threshold was assessed 1 and 5 minutes after application to the cornea and at 5- minute intervals thereafter for 60 minutes. RESULTS: Corneal sensitivity, as determined by Cochet-Bonnet aesthesiometry, was significantly reduced from baseline for 25 minutes following topical administration of ophthalmic proparacaine. Maximal anesthetic effect lasted 5 minutes. CONCLUSIONS AND CLINICAL RELEVANCE: As determined by Cochet-Bonnet aesthesiometry, duration of anesthetic effects on the cornea induced by a single topical application of an ophthalmic preparation of 0.5% proparacaine solution in DSH cats is considerably shorter than the reported duration of corneal anesthesia in dogs.

Duration of effect and effect of multiple doses of topical ophthalmic 0.5% proparacaine hydrochloride in clinically normal dogs.

OBJECTIVE: To determine the duration of effect and the effect of multiple doses of topical ophthalmic application of 0.5% proparacaine hydrochloride on corneal sensitivity in clinically normal dogs. ANIMALS: 8 clinically normal dogs. PROCEDURE: Dogs were randomly allocated to treatment order in a 2 x 2 (period X treatment) crossover study. Treatments consisted of topical application of ophthalmic 0.5% proparacaine (1 drop or 2 drops at a 1-minute interval); treatments were applied to both eyes. A Cochet-Bonnet aesthesiometer was used to determine corneal touch threshold (CTT) before corneal application, 1 and 5 minutes after corneal application, and at 5-minute intervals thereafter for 90 minutes. RESULTS: The CTT value before treatment differed significantly from CTT values after treatment until 45 minutes after application in the 1-drop group and until 55 minutes after application in the 2-drop group. As determined by use of the Cochet-Bonnet aesthesiometer, a significantly greater anesthetic effect was detected for the 2-drop treatment, compared with the effect for the 1-drop treatment, at 30, 35, 40, 45, 50, and 55 minutes after application. Maximal anesthetic effect lasted for 15 minutes for the 1-drop treatment and 25 minutes for the 2-drop treatment. CONCLUSIONS AND CLINICAL RELEVANCE: Duration of corneal anesthetic effect induced by topical ophthalmic application of 0.5% proparacaine in dogs of this study is considerably longer than that reported elsewhere. Serial application of doses of 0.5% proparacaine increases the duration and magnitude of corneal anesthetic effects.

Effect of topical anesthesia on episcleral venous pressure in normal human subjects.

PURPOSE: Topical anesthetics can reduce episcleral venous pressure (EVP) and IOP in rabbits. In this study, we investigated the effect of topical anesthesia on EVP in normal human subjects. METHODS: We included in this study 30 eyes of 15 healthy volunteers who were habitual soft contact lens wearers. The EVP was measured before and at 5 and 10 minutes after instillation of topical proparacaine 0.5% in one eye. The EVP was measured by using a custom objective venomanometer. We compared EVP at 5 and 10 minutes after proparacaine to EVP before instilling proparacaine. RESULTS: There was no significant difference between EVP in eyes receiving topical anesthetic at 5 or 10 minutes (7.2 ± 2.2 and 7.6 ± 2.7 mm Hg, respectively; mean ± SD) compared to contralateral eyes (6.9 ± 2.5 and 7.3 ± 2.6 mm Hg, respectively; P > 0.10). As well, EVP was not significantly different 5 or 10 minutes after topical anesthesia compared to baseline in either the eyes receiving anesthetic or the contralateral eyes (all P > 0.10; minimum detectable difference, 1.4-1.9 mm Hg, α = 0.05, ß = 0.20, n = 30 eyes). CONCLUSIONS: The EVP in human eyes is not affected significantly by topical anesthetics.

Corneal sensitivity following lacrimal gland excision in the rat.

PURPOSE: Dry eye disease (DED) produces ocular pain and irritation, yet a detailed characterization of ocular sensitivity in a preclinical model of DED is lacking. The aim of the present study was to assess nociceptive behaviors in an aqueous tear deficiency model of DED in the rat. METHODS: Spontaneous blinking, corneal mechanical thresholds, and eye wipe behaviors elicited by hypertonic saline (5.0 M) were examined over a period of 8 weeks following the unilateral excision of either the exorbital lacrimal gland or of the exorbital and infraorbital lacrimal glands, and in sham surgery controls. The effect of topical proparacaine on spontaneous blinking and of systemic morphine (0.5-3.0 mg/kg, subcutaneous [SC]) on spontaneous blinking and eye wipe responses were also examined. RESULTS: Lacrimal gland excision resulted in mechanical hypersensitivity and an increase in spontaneous blinking in the ipsilateral eye over an 8-week period that was more pronounced after infra- and exorbital gland excision. The time spent eye wiping was also enhanced in response to hypertonic saline (5.0 M) at both 1- and 8-week time-points, but only in infra- and exorbital gland excised animals. Morphine attenuated spontaneous blinking, and the response to hypertonic saline in dry eye animals and topical proparacaine application reduced spontaneous blinking down to control levels. CONCLUSIONS: These results indicate that aqueous tear deficiency produces hypersensitivity in the rat cornea. In addition, the increase in spontaneous blinks and their reduction by morphine and topical anesthesia indicate the presence of persistent irritation elicited by the activation of corneal nociceptors.

Comparison of proteins in lacrimal gland fluid secreted in response to different stimuli.

To determine if different stimuli cause secretion of different proteins in lacrimal gland fluid (LGF), rabbits were anesthetized and LGF collected under baseline conditions (with the local anesthetic proparacaine), with ocular reflexes present, and in response to arterial injection of the cholinergic agonist acetylcholine (ACh) or the peptide vasoactive intestinal peptide (VIP). Proteins in LGF were separated by nondenatured gradient polyacrylamide gel electrophoresis. Except for minor differences, the number, the approximate molecular weights, and the amounts were the same in LGF secreted in response to four different stimuli. We concluded that the different stimuli caused protein release either from the same secretory cells or from different populations of secretory cells with the same secretory proteins.

Eosinophil chemotaxis and anterior uveitis from topical dimaprit and nordimaprit.

Topical application of the H2-histamine receptor agonist, dimaprit (S-[4-N,N-dimethylaminopropyl]isothiourea), produced eosinophil chemotaxis into the anterior segment of rabbit eyes only when an H2-antagonist was co-administered. Nordimaprit (S-[4-N,N-dimethylaminoethyl]isothiourea), a structural homologue of dimaprit that lacked activity at histamine receptors, produced eosinophil chemotaxis whether or not an H2-antagonist was co-administered. Onset of eosinophil chemotaxis began after 2 or more days of treatment, and was accompanied by corneal edema, opacification, and ocular inflammation. There was no concurrent eosinophilia in the peripheral blood or in the conjunctiva. The response occurred in pigmented and albino rabbit eyes, and was facilitated by prior co-administration of proparacaine eye drops. Another dimaprit homologue without activity at histamine receptors, homodimaprit (S-[4-N,N-dimethylaminobutyl]isothiourea), did not produce eosinophil chemotaxis when applied topically, nor did the H2-agonists impromidine, histamine, or 4-methylhistamine, whether co-administered with an H2-antagonist or not. It was concluded that dimaprit and nordimaprit produced a selective eosinophil chemotaxis unrelated to H1- and H2-histamine receptor activity. However, the H2-agonist activity of dimaprit appeared to inhibit this response unless neutralized by an H2-antagonist. Topical application of dimaprit with an H2-antagonist or nordimaprit alone may allow large numbers of non-degranulated eosinophils, free of other cell types, to be harvested from the aqueous humor.

Schirmer test after topical anesthesia and the tear meniscus height in normal eyes.

The height of the inferior tear meniscus was measured in 86 normal eyes. A value greater than 0.1 mm was obtained in 93% of the eyes that were studied. However, attempts to correlate meniscus height with subsequent Schirmer test results showed that these measurements varied randomly. Schirmer tests that were conducted on 265 eyes without instillation of 0.5% proparacaine hydrochloride and on 466 eyes with proparacaine showed that topical anesthesia reduced mean test values by 40%. When proparacaine was used prior to testing, no decrease in tear production with advancing age was demonstrated, nor were results significantly different in males and females. Schirmer test values, ranging from 0 to 3 mm, were obtained in 15% of the normal volunteers when the test was performed after instillation of topical anesthesia and after blotting of the tear lake from the inferior cul-de-sac.

Schirmer's test. A closer look.

In 50 normal subjects, results of kinetics studies of Schirmer's test demonstrated nonlinear wetting with an initial rapid phase of wetting followed by a progressive reduction in rate. This initial rapid phase of wetting indicated a reflex secretion of tears. In the majority of subjects, topical anesthesia with 0.5% proparacaine hydrochloride dampened the initial reflex secretion but could not completely suppress it. The data indicated that Schirmer's test with anesthesia was not capable of measuring a basic tear secretion independent of reflex components.

The reinforcing properties of procaine, chloroprocaine and proparacaine in rhesus monkeys.

Responding was maintained under a fixed ratio 10 schedule of intravenous cocaine (six monkeys) or pentobarbital (two monkeys) delivery during a daily 3 h session. When responding was stable, intravenous doses of procaine (0.05--3.2 mg/kg), chloroprocaine (0.05--3.2 mg/kg), proparacaine (0.01--0.4 mg/kg), or saline were substituted for the cocaine or pentobarbital for six to ten sessions. Between each substitution, responding was again maintained by cocaine or pentobarbital. Procaine and chloroprocaine maintained rates of responding exceeding saline levels in all monkeys tested, with maximum rates generated by 0.2 mg/kg. Daily intake in mg/kg increased 3--10 times a dose was increased from 0.1 to 3.2 mg/kg per infusion. Within each session, there were periods of continuous responding resulting in multiple infusions, separated by intervals of no responding of varying duration. Nevertheless, the number of infusions occurring in each of the six 30 min periods was relatively constant for both drugs. Responding maintained by proparacaine was similar or slightly above that maintained by saline except at one dose (0.025 mg/kg) in one monkey. No signs of toxicity were observed with any of the drugs. These results indicate that procaine and chloroprocaine are strong positive reinforcers but that proparacaine has minimal reinforcing properties.

Voltage-dependent sodium channels in synaptoneurosomes: studies with 22Na+ influx and [3H]saxitoxin and [3H]batrachotoxinin-A 20-alpha-benzoate binding. Effects of proparacaine isothiocyanate.

22Na+ influx and binding of [3H]saxitoxin ([3H]STX) and [3H]batrachotoxin-A 20-alpha-benzoate ([3H]BTX-B) were studied in guinea pig cerebral synaptoneurosomes. STX and tetrodotoxin (TTX) completely blocked the stimulation of sodium influx induced by 1 microM BTX. The IC50 values for STX and TTX closely matched the Ki values for inhibition of [3H]STX binding, suggesting that the sites labelled by [3H]STX are associated with a population of BTX-sensitive channels. BTX induced a dose-dependent stimulation of sodium influx in synaptoneurosomes (EC50 280 nM). The potency of BTX for stimulation of sodium influx was increased (EC50 24 nM) in the presence of 0.6 microgram/ml scorpion venom without any change in maximal influx. In contrast, specific binding of [3H]BTX-B to synaptoneurosomes was minimal in the absence of scorpion venom, but it was increased several fold in the presence of 60 micrograms/ml scorpion venom. With proparacaine isothiocyanate (PROPRIT), an irreversible local anesthetic, the inhibition of [3H]BTX-B binding by PROPRIT did not occur in parallel with an inhibition of sodium influx induced by BTX. Preincubation of synaptoneurosomes with 10 microM PROPRIT for 10 min resulted in approximately 70% inhibition of [3H]BTX-B binding in the presence of scorpion venom. Such preincubation did not alter BTX-induced sodium uptake in synaptoneurosomes. Preincubations of synaptoneurosomes with 100 microM PROPRIT for 10 min completely inhibited [3H]BTX-B binding, and under these conditions BTX-induced sodium influx was reduced only by 50%. The results indicate that virtual elimination of binding sites labeled by [3H]BTX-B in the presence of scorpion venom by PROPRIT has little effect on sodium influx induced by BTX.(ABSTRACT TRUNCATED AT 250 WORDS)

Pupillary dilatation with single eyedrop mydriatic combinations.

We studied the mydiatic effect of three solutions containing a combination of two mydriatic drugs in 80 adult patients. The solutions tested were cyclopentolate HCl 0.5% with phenylephrine 2.5%, tropicamide 0.5% with phenylephrine 2.5%, and tropicamide 1.0% with phenylephrine 2.5%. We evaluated the effect of prior instillation of proparacaine 0.5% eyedrops. All three mydriatic combination solutions evaluated produced pupillary dilatation of about 7 mm within 60 minutes. Additional pupillary dilatation of 1 mm occurred when proparacaine was instilled before the mydriatic combination eyedrop. Mydriasis was resistant to bright light during indirect ophthalmoscopy in all patients. Pupils of younger patients dilated better than those of older patients, but sex and iris color were factors in the amount of pupillary dilatation obtained. Wide and sustained pupillary dilatation can be obtained for satisfactory indirect ophthalmoscopy by the instillation of one drop of proparacaine solution followed by a single drop of any of the three mydriatic combination solutions evaluated. By eliminating the need for multiple instillations of drugs, the use of a single eyedrop mydriatic combination is convenient in terms of time saved and also lessens the change of systemic drug toxicity.