Exacerbation of akinetic seizures by atropine eye drops

Combination of 5% phenylephrine and 0.5% tropicamide eyedrops for pupil dilation in neonates is twice as effective as 0.5% tropicamide eyedrops alone

PURPOSE

Comparison of the efficacy of tropicamide eyedrops to the combination of 0.5% tropicamide and 5% phenylephrine eyedrops in order to achieve a proper dilation in premature infants undergoing screening for retinopathy of prematurity.

METHODS

A prospective, randomized, double-blind study was conducted to compare the efficacy of two mydriatic regimens: one regimen consisting of three drops of 0.5% tropicamide (TTT regimen), the other regimen consisting of one drop of 5% phenylephrine and two drops of 0.5% tropicamide (PTT regimen). Thirty premature infants were enrolled and received both mydriatic regimens: one regimen in each eye. Outcomes were pupil dilation evaluated by the percentage of pupil diameter over cornea diameter, the percentage of pupil surface over cornea surface and the quality of the eye fundus examination.

RESULTS

The percentage of pupil diameter over cornea diameter was 47.3% (±8.7) with the TTT regimen and 65.9% (±8.8) with the PTT regimen (p < 0.0001). The percentage of pupil surface over cornea surface was 23.1% (±8.3) with the TTT regimen and 43.8% (±7.3) with the PTT regimen (p < 0.0001). Thus, the pupil surface area was 1.9 times greater with the PTT than with the TTT regimen. Visualization of the retinal periphery was possible for 30 of 30 eyes dilated with the PTT regimen and for 16 of 30 eyes dilated with the TTT regimen (p < 0.0001).

CONCLUSION

The dilated pupil surface area for the combination of 5% phenylephrine and 0.5% tropicamide was almost twice that for 0.5% tropicamide eyedrops alone and provided significantly superior quality of the eye fundus examination.

Epileptic seizures induced by cycloplegic eye drops

OBJECTIVE

To assess the incidence of seizures induced by cycloplegic ophthalmic drops.

MATERIALS AND METHODS

A survey among members of the American Association for Pediatric Ophthalmology and Strabismus yielded five patients who received cycloplegic eye drops between 1998 and 2010 and who consequently developed a seizure.

RESULTS

The median age of the patients was 5 years (range 3 months to 12 years). Cyclopentolate hydrochloride 1% was the only causative agent. The seizure happened on average 12 min after the instillation of dilating eye drops. Three were generalized convulsions, and two patients had a focal seizure. Past medical history was unremarkable in four cases. In total, 16 previous cases of seizures induced by cycloplegic drugs were identified in reports published between 1890 and 2004, implicating atropine in nine reports, tropicamide and phenylephrine eye drops in one and cyclopentolate in six.

DISCUSSION

A small amount of cyclopentolate drops could induce convulsions in young children after only minutes to less than an hour, while a larger dosage of atropine over the span of several hours could cause this rare and unpredictable complication. Predisposing factors were rare and those developing the seizures were healthy subjects. Generalized seizures were much more frequent than focal convulsions.

CONCLUSIONS

Seizures after instillation of cycloplegic drops are extremely rare.

Pharmacokinetic and Pharmacodynamic Evaluations of the Zwitterionic Metabolite of a New Series of N-Substituted Soft Anticholinergics

PURPOSE

This study was conducted to evaluate the zwitterionic common metabolite of a novel series of N-substituted soft analogs of glycopyrrolate both as racemates and as 2R isomers.

METHODS

Activities were assessed using both in vitro (receptor binding assay, guinea pig ileum pA2 assay) and in vivo techniques (rabbit mydriatic response, rat cardiac effects). Pharmacokinetic characterizations in rats were also performed.

RESULTS

The metabolite was highly water-soluble and very stable in buffer solutions as well as in rat biological media. Following i.v. administration in rats, it was very rapidly eliminated, mainly through renal excretion with a half-life of about 10 min. Receptor binding and guinea pig ileum assays indicated this metabolite as more than 1 order of magnitude less active than its parent soft drugs or glycopyrrolate. Moderate M3/M2 muscarinic receptor subtype selectivity was observed, further reducing the likelihood of cardiac side effects. The metabolite showed to some extent mydriatic effect and protective effect against carbachol-induced bradycardia, but of much shorter durations than glycopyrrolate; it had, however, no effect on resting heart rate.

CONCLUSIONS

N-Substituted zwitterionic metabolites retain some, but only considerably reduced activity of their parent quaternary ammonium ester soft anticholinergic drugs, and they are very rapidly eliminated from the systemic circulation. They are suitable for their assigned role within the framework of inactive metabolite-based soft anticholinergic design.

Design, pharmacokinetic, and pharmacodynamic evaluation of a new class of soft anticholinergics

PURPOSE

To design and evaluate a new class of soft anticholinergics with subtype selectivity.

METHODS

A new class of soft anticholinergics was designed based on the "inactive metabolite" approach. Four compounds were synthesized. The potency and soft nature of the compounds were evaluated by receptor binding, cardiac, and mydriatic studies. Stability and pharmacokinetic studies were also performed on these newly synthesized soft anticholinergics.

RESULTS

Receptor binding studies of the soft anticholinergics on cloned muscarinic receptors indicated pKi values in the range of 7.5 to 8.9. Two compounds, 9a and 13a, of the series showed muscarinic subtype receptor selectivity (M3/M2). In mydriatic studies, 13a and 13b showed shorter duration of action in the treated eyes than tropicamide. In the control eyes, significant dilation of pupils was found only in rabbits treated with atropine and tropicamide, indicating that the soft anticholinergics lack systemic effects because of their facile hydrolytic deactivation. Consistent with their soft nature, this new class of soft anticholinergics displayed much shorter cardiovascular effects in the carbachol-induced bradycardia (10 to 15 min) in rats than atropine (> 60 min). Stability and pharmacokinetic studies suggested that the new soft anticholinergics were rapidly eliminated from plasma (systemic circulation) after i.v. administration.

CONCLUSIONS

A new class of anticholinergics was designed and synthesized, and the PK/PD evaluation confirmed they were potent "soft" anticholinergics; two of them showed muscarinic receptor subtype selectivity (M3/M2).

Eye drops--the hidden poison

Eye drops are very commonly prescribed but their potential for systemic absorption and serious toxicity may be forgotten. This paper examines patterns of prescription of eye drops in Scotland by general practitioners. A review of the serious systemic features and toxicity, and their management, of commonly used eye drops is undertaken. Practical recommendations for the monitoring of such effects in clinical practice are made.

Soft drugs--XVI. Design, evaluation and transdermal penetration of novel soft anticholinergics based on methatropine

Atropine has been reported to produce unwanted systemic side effects on topical administration into the eye. The same problem could arise when atropine is used topically as a suppressant of eccrine sweating. In this study, the principles of soft drug design were applied to methatropine. A hypothetical carboxylate metabolite of methatropine was reactivated by esterification with cyclic and alicyclic alcohols to yield a series of compounds (3a-g). In vitro evaluation by guinea pig ileum assay indicated that the compounds are potent anticholinergics and the lead carboxylate metabolite is about 60 times less potent than the most active compound of the series. The activity was found to decrease with the increasing side chain length. The n-octanol/water partition coefficients were found to be directly dependent on the chain length for the compounds made with straight chain alcohols. The transdermal permeability coefficients across the hairless mice skin were found to be directly dependent on the partition coefficients. The soft drugs are found to metabolize extensively during the penetration process compared to the unmetabolizable nature of methatropine. The soft drugs reported in this study will probably be able to elicit a local action at the site of application but will probably be metabolized rapidly in the systemic circulation, thereby avoiding the systemic side effects with a consequent increase in the therapeutic index.