Tropicamide

Tropicamide is an anticholinergic and a Muscarinic Receptor subtype M4-preferring antagonist .Tropicamide is an antimuscarinic drug that produces short acting mydriasis (dilation of the pupil) and cycloplegia when applied as eye drops. It is used to allow

Time-Course of Changes in Choroidal Thickness after Complete Mydriasis Induced by Compound Tropicamide in Children.[Pubmed:27622495]

PLoS One. 2016 Sep 13;11(9):e0162468.

PURPOSE: The aim of this study was to investigate the time-course of changes in choroidal thickness (ChT) following complete mydriasis induced by compound Tropicamide. METHODS: ChT was measured by OCT with the enhanced-depth imaging technique (Spectralis HRA+OCT, Heidelberg Engineering, Germany) at nine locations of the fundus: subfoveal ChT (SFChT) and ChT at 1 mm and 3 mm from the fovea in four quadrants. Mydriasis was induced with compound Tropicamide (0.5% Tropicamide plus 0.5% phenylephrine hydrochloride, three doses at 5-minute intervals). Measurements were conducted prior to the instillation and at 0, 30, and 60 min following complete mydriasis. Results at different time-points were compared using repeated-measures ANOVA to investigate the time-course of the changes. RESULTS: Thirty-nine subjects (mean age 11.9+/-2 years; 16 males and 23 females) were enrolled in the study. Compound Tropicamide resulted in a statistically significant decrease in SFChT at 0, 30, and 60 min after complete mydriasis, as compared to baseline (-5+/-4 mum, -12+/-4 mum, and -13+/-4 mum, respectively; all P<0.0001). No significant changes were detected in the parafoveal choroid except at 1 mm temporal (T1mm) and nasal (N1mm) to the fovea at 30 and 60 min (T1mm: -6+/-4 mum and -7+/-5 mum at 30 and 60 min; N1mm: -6+/-4 mum and -7+/-5 mum at 30 and 60 min, respectively; all P<0.0001). Repeated-measures ANOVA showed a significant interaction between the time after complete mydriasis and the effect of the mydriasis agent. CONCLUSIONS: Complete mydriasis induced by compound Tropicamide led to choroidal thinning, and the magnitude varied over time.

Correction: Time-Course of Changes in Choroidal Thickness after Complete Mydriasis Induced by Compound Tropicamide in Children.[Pubmed:28166303]

PLoS One. 2017 Feb 6;12(2):e0171924.

[This corrects the article DOI: 10.1371/journal.pone.0162468.].

Higher-Order Aberrations After Cyclopentolate, Tropicamide, and Artificial Tear Drops Application in Normal Eyes.[Pubmed:27749472]

Eye Contact Lens. 2018 Mar;44(2):109-112.

PURPOSE: To determine the effect of cyclopentolate, Tropicamide, and artificial tear drops on higher-order aberrations (HOAs) in normal eyes with OPD-Scan III (Nidek Inc., Tokyo, Japan). METHODS: In this study, 189 eyes of individuals aged 20 to 35 years were selected as samples. Inclusion criteria were a corrected visual acuity of 20/20 or better, a minimum size of about 5 mm for the pupil in the dark, hyperopia and myopia less than 5 D, and astigmatism less than 2 D. Moreover, participants with pathological eye problems, a history of intraocular surgery, and ocular diseases affecting the accommodation, pupil size, and corneal surface were excluded. Higher-order aberrations of the participants were assessed by the OPD-Scan III before and after cyclopentolate (Colircuss), Tropicamide (Mydrax 0.5%), and artificial tears (Tearlose) drop instillation. RESULTS: After instilling cyclopentolate drops, the mean of the total root mean square (RMS) increased from 4.580 to 6.335 D, total spherical aberration increased from 0.155 to 0.381 D, and total coma increased from 0.195 to 0.369 D; the increases were significant for total RMS and total spherical aberration, but a significant relationship was not seen with total coma. After Tropicamide, the mean aberrations of total RMS increased from 4.301 to 4.568 D, total spherical aberration increased from 0.146 to 0.160 D, and total coma increased from 0.213 to 0.230 D; the increase was only significant for total coma. On the other hand, after artificial tears, the average of all aberrations decreased in a nonsignificant manner. CONCLUSION: Most changes of mean aberrations were related to cyclopentolate drops. Tropicamide and artificial tears had the second and third rank according to their effect on mean errors. As a result, it seems that ocular accommodation is the most important impact on HOA than pupil size. However, the pupil size is the second factor for HOAs.

Early signal of diverted use of tropicamide eye drops in France.[Pubmed:28239898]

Br J Clin Pharmacol. 2017 Aug;83(8):1791-1800.

AIMS: Tropicamide is a mydriatic drug used as eye-drops for diagnostic or therapeutic purposes. From 2013, a diverted use by intravenous route has been suspected in Eastern Europe in opioids users. To date, no signal of misuse has been identified in France. The aims of this study were to investigate any early signals of a diverted use of Tropicamide eye drops and to collect information regarding motives for the misuse and Tropicamide-induced effects. METHODS: Information was obtained at three levels: (1) at regional level (Midi-Pyrenees area), from reimbursement data and pharmacists' reports on suspicious requests; (2) at national level: from reimbursement data and prescriptions suggesting possible abuse from the OSIAP (Ordonnances Suspectes, Indicateur d'Abus Possible) survey; and (3) at international level: from VigiBase((R)) reports and Web sources. Beta-blocker eye-drops were used as comparators. RESULTS: In France, in 2014-2015, 17 (0.91%, 95% CI [0.53-1.46%]) falsified prescriptions involving Tropicamide were identified in the OSIAP survey (compared with 0%, 95% CI [0-0.19%] for beta-blockers). Moreover, 37 other suspicious prescriptions were presented in 2015 (notified in 2016). In Midi-Pyrenees, seven patients aged 35-49 were reimbursed for 19-45 vials of 10 ml, in a year. Since September 2014, the regional Addictovigilance Centre has received 91 notifications of suspicious requests to obtain Tropicamide. In VigiBase((R)) , two cases were identified but none in France. An increased interest in Tropicamide-related Internet searches was observed from Russia and Ukraine. CONCLUSIONS: These results represent the first early warnings of a Tropicamide diverted use in France. Tropicamide abusers would seek euphoria or hallucinations. The high doses involved in intravenous administration could lead to serious complications.

Different muscarinic receptor subtypes mediating the phasic activity and basal tone of pig isolated intravesical ureter.[Pubmed:7905771]

Br J Pharmacol. 1993 Dec;110(4):1413-20.

1. We have studied the effects of muscarinic cholinoceptor agonists and specific antagonists on both phasic activity and basal tone of the isolated intravesical ureter of the pig by means of isometric techniques in vitro. 2. Acetylcholine in the presence and absence of physostigmine increased both phasic activity and basal tone of ureteral strips in a concentration-dependent manner. Moreover carbachol, methacholine and oxotremorine-M increased both contractile parameters while bethanechol and McN-A-343 evoked only increases in tone without affecting the frequency of the phasic contractions. 3. The nicotinic receptor blocker, hexamethonium (10(-6)-10(-4) M), failed to modify the contractions evoked by a single dose of carbachol (10(-5) M), whilst the muscarinic antagonist, atropine inhibited both phasic and tonic responses. 4. The muscarinic M1 (pirenzepine), M2 (AF-DX 116 and methoctramine), M3 (4-DAMP, HHSiD and p-F-HHSiD), and putative M4 receptor (Tropicamide) antagonists significantly reversed increases in both frequency of phasic activity and baseline tone induced by a submaximal dose of carbachol (10(-5) M). The pIC50 values for inhibition of the induced phasic activity were: atropine (10.16) > 4-DAMP (9.12) > HHSiD (8.22) = methoctramine (7.98) = p-F-HHSiD (7.88 > Tropicamide (7.62) = pirenzepine (7.53) = AF-DX 116 (7.45) and for inhibition of basal tone were: atropine (10.73) > 4-DAMP (9.32) > HHSiD (8.65) = pirenzepine (8.43) = p-F-HHSiD (8.38) > methoctramine (7.79) > Tropicamide (7.53) > AF-DX 116 (7.04). 5. The antagonist profile indicates that an M1 receptor mediates the tonic response while the phasic activity could involve either both M2 and M3 or an M4 muscarinic receptor. These results suggest that different muscarinic receptor subtypes mediate the phasic and tonic contractile activity induced by a submaximal concentration of carbachol in the porcine intravesical ureter.

Characterization of muscarinic M4 binding sites in rabbit lung, chicken heart, and NG108-15 cells.[Pubmed:2250662]

Mol Pharmacol. 1990 Dec;38(6):805-15.

We have carried out an extensive pharmacological characterization of muscarinic binding sites in rabbit lung and chicken heart in parallel with M1, M2, and M3 sites, [3H]Pirenzepine, a selective antagonist at M1 receptors, bound saturably and reversibly to membranes from chicken heart and rabbit lung. These binding sites were not M1 receptors, however, because the cardioselective antagonist himbacine had 10-fold higher affinity at these sites than at [3H]pirenzepine sites in rat and rabbit cortex (true M1 sites). We measured the inhibitory potency of 28 antagonists at [3H]N-methylscopolamine-labeled sites in chicken heart, rabbit lung, rat heart (M2 sites), and rat submandibular gland (M3 sites) and at M1 sites in rat cortex. The sites in rabbit lung were different from M1, M2, and M3 sites, because they had moderate to high affinity for M1-selective compounds (pirenzepine and telenzepine), M2-selective compounds (himbacine and methoctramine), and M3-selective compounds (hexahydrosiladifenidol and 4-diphenylacetoxy-N-methylpiperidine methiodide). The sites in chicken heart resembled most those in rabbit lung, with similar high affinity for secoverine, but they were not the same because Tropicamide, diphenylacetoxybutynyl dimethylamine, and [3H]-N-methylscopolamine were more potent in rabbit lung. In a further series of experiments, we compared the affinity of six of the most discriminating antagonists in membranes from rabbit lung and NG108-15 cells, a neuroblastoma-glioma cell line reported to express the muscarinic m4 receptor gene. The antagonists had very similar affinities in the two tissues, the largest discrepancy being that pirenzepine was twice as potent in rabbit lung as in NG108-15 cells. Northern blots using probes designed to discriminate between five species of muscarinic receptor RNA detected only m4 mRNA in rabbit lung. We conclude that rabbit lung contains a muscarinic M4 binding site with a quite distinctive pharmacology and that chicken heart contains a receptor with similarities to the M4 sites. This is the first report to characterize native M4 binding sites in a nonneuronal mammalian tissue.