Atropine toxicity

Stepwise candidate drug screening for myopia control by using zebrafish, mouse, and Golden Syrian Hamster myopia models

Background

We developed a preclinical protocol for the screening of candidate drugs able to control myopia and prevent its progression. The protocol uses zebrafish, C57BL/6 mice, and golden Syrian hamster models of myopia.

Methods

A morpholino (MO) targeting the zebrafish lumican gene (zlum) was injected into single-cell zebrafish embryos, causing excessive expansion of the sclera. A library of 640 compounds with 2 matrix metalloproteinase (MMP) inhibitors (marimastat and batimastat), which have the potential to modulate scleral remodelling, was screened to identify candidates for mitigating scleral diameter expansion in zlum-MO-injected embryos. The myopia-prevention ability of compounds discovered to have superior potency to inhibit scleral expansion was validated over 4 weeks in 4-week-old C57BL/6 mice and 3-week-old golden Syrian hamsters with form-deprivation myopia (FDM). Changes in the refractive error and axial length were investigated. Scleral thickness, morphology of collagen fibrils in the posterior sclera, messenger RNA (mRNA) expressions, and protein levels of transforming growth factor-β2 (TGF-β2), tissue inhibitor of metalloproteinase-2 (TIMP-2), MMP-2, MMP-7, MMP-9, and collagen, type I, alpha 1 (collagen Iα1) were investigated in C57BL/6 mice, and MMP-2, MMP-9, and MMP activity assays were conducted in these mice.

Findings

In the zebrafish experiment, atropine, marimastat, batimastat, doxycycline, and minocycline were the drugs that most effectively reduced expansion of scleral equatorial diameter. After 28-day treatment in diffuser-wearing mice and 21-day treatment in lid-sutured hamsters, myopic shift and axial elongation were significantly mitigated by eye drops containing 1% atropine, 50 µM marimastat, 5 µM batimastat, or 200 µM doxycycline. MMP-2 mRNA expression in mouse sclera was lower after treatment with atropine, marimastat, batimastat, or doxycycline. The protein levels and activity of MMP-2 and MMP-7 were significantly reduced after treatment with atropine, marimastat, batimastat, doxycycline, and minocycline. Furthermore, scleral thickness and collagen fibril diameter were not lower after treatment with atropine, marimastat, batimastat, or doxycycline than those of occluded eyes.

Interpretation

Stepwise drug screening in a range of models from zlum-MO-injected zebrafish to rodent FDM models identified effective compounds for preclinical myopia control or prevention. On the basis of the 640 compounds that were screened, MMP inhibitors may offer alternatives for clinical trials.

Funding

This research was supported by grants from Taiwan's Ministry of Science and Technology and Ministry of Health and Welfare.

Adrenaline is effective in reversing the inadequate heart rate response in atropine treated organophosphorus and carbamate poisoning

BACKGROUND

In acute organophosphorus (OP) or carbamate poisoning, some patients require high dose atropine to counteract the effects on heart rate (HR) and blood pressure (BP). This study describes the factors associated with high dose atropine therapy and the use of adrenaline to reverse the inadequate HR response to atropine.

METHODS

Consecutive patients admitted to the intensive care unit (ICU) were prospectively recruited. Demographic data, treatment and outcomes of patients who failed to achieve target HR (100/min) or systolic BP >90 mm Hg with either a cumulative atropine dose of 100-mg within 6-h following admission or an infusion of 30 mg/h for at least 3-h were compared with patients who achieved the targets. Factors associated with high dose atropine therapy were explored using logistic regression analysis and expressed as odds ratio (OR) with 95% confidence intervals (CIs).

RESULTS

Of the 181 patients admitted with OP or carbamate poisoning, 155 patients fulfilled inclusion criteria. The mean (SD) age was 35.7 (15.8) years; admission APACHE-II score was 14.6 (7.5). Heart rate and/or BP target was not achieved in 13.6%. In these patients, target HR was achieved after adding adrenaline infusion at 2-4 μg/min. Ventilation duration (11.6 ± 6.3 vs. 8.4 ± 6.9 days, p = 0.05) and ICU stay (12.3 ± 5.8 vs. 8.9 ± 5.8 days, p = 0.01) were longer in patients requiring high dose atropine when compared with others. On multivariate logistic regression analysis, shorter time to presentation to hospital (p = 0.04) was associated with need for high dose atropine. Overall mortality was 9% and similar in both groups (p = 0.41).

CONCLUSIONS

High dose atropine therapy is required in a subset of patients with OP and carbamate poisoning and was associated with longer ventilation duration and ICU stay. Adrenaline infusion improved hemodynamics in these patients.

Atropine toxicity caused by erroneous intranasal administration in a pediatric patient: case report

A 28-month-old boy mistakenly received intranasal atropine sulfate instead of Otrivin (xylometazoline hydrochloride) for the treatment of adenoid hypertrophy. Later on, he came to the emergency department with anticholinergic manifestations after the administration of multiple drops. The child presented with a tonic-clonic seizure lasting for a few minutes, followed by a brief loss of consciousness, vomiting, agitation, and irritability, all of which were stabilized by a dose of intravenous lorazepam. Subsequently, he was admitted to the pediatric intensive care unit for observation. Afterwards, he developed agitation and unsteady gait, both of which resolved after receiving neostigmine. Eventually, the child became asymptomatic and was discharged home. To the best of our knowledge, only one similar case has been reported in the literature. SIMILAR CASES PUBLISHED: 1.

Acute methaemoglobinaemia initially treated as organophosphate poisoning leading to atropine toxicity

A case of unknown compound poisoning is presented. It was initially treated as organophosphate poisoning with lack of response. A timely diagnosis of acute methaemoglobinaemia and iatrogenic atropine toxicity was made based on clinical evaluation. Treatment of methaemoglobinaemia using oral methylene blue and of atropine toxicity with supportive measures could save the patient.

Exacerbation of akinetic seizures by atropine eye drops

A case is reported where atropine sulphate eye drops increased the frequency of fits in a child suffering regular akinetic seizures. This increase was marked and observed during two separate courses of eye drops. This is discussed with reference to previous reports of central nervous toxicity after the use of topical atropine sulphate.

Cycloplegic refraction in children: single-dose-atropinization versus three-day-atropinization

A new scheme for refractive measurements under atropine cycloplegia was tested in 90 strabismic children aged two to several years. Refraction was determined by an autorefractor (CANON R 10) 90 minutes after application of two drops of atropine (0.5% atropine children < 2 1/2 years; 1.0% atropine children > 2 1/2 years) and compared with the results after 3 days of receiving 1 atropine eyedrop 3 times daily. In 86.5% the spherical equivalents differ not more than 1.0 diopter (p = 0.05); the correlation was 0.99. Astigmatic corrections were in agreement in 95.5%, the axis of cylinders in 93.0% (p = 0.05); the correlations were 0.95 and 0.97. The residual accommodation 90 minutes after 2 drops of atropine was not more than 1 diopter in all children. The additional cycloplegic effect of the three-day-atropinization was only 0.5 diopters. This new type of application allows a more rapid and less toxic assessment of refraction than the usual three-day-atropinization.

Systemic atropine administration during cardiac arrest does not cause fixed and dilated pupils

OBJECTIVES

Systemic administration of atropine during CPR may postpone brain death determination because of its reputed ability to produce fixed and dilated pupils. We studied the effect of atropine administered in the usual doses as an adjunct to endotracheal intubation and for cardiac arrest to determine if it would interfere with neurological assessment.

DESIGN

Two groups of children were studied. Group 1 consisted of 28 patients who received atropine (0.03 +/- 0.003 mg/kg) prior to endotracheal intubation. Group 2 consisted of 21 patients previously without evidence of brainstem disease who suffered a witnessed arrest and had prompt return of spontaneous circulation and received an atropine dose of 0.03 +/- 0.01 mg/kg.

RESULTS

In group 1, pupillary size averaged 4.02 +/- 0.78 mm before and 4.75 mm +/- .84 mm after atropine (P less than .001). In group 2, the pupillary examination was conducted 30 minutes after return of spontaneous circulation. The pupillary diameter was 4.80 +/- 0.91 mm. All pupils were reactive to light in both groups.

CONCLUSION

Atropine administration in conventional dose causes slight pupillary dilation but does not abolish pupillary light reactivity.

Anaphylactic reaction after atropine

A 38-year-old woman developed symptoms of anaphylactic shock after intravenous atropine and required adrenaline to maintain perfusion pressure. A strongly positive response was obtained on intradermal testing. The Prausnitz-Kuestner test was also positive, which indicated the presence of drug specific IgE antibodies. No response was obtained after hyoscine.