Cyclopentolate systemic effects

Central Nervous System Disorders. Clinicians should be cautious when using topically applied central nervous system stimulants such as cyclopentolate. High concentrations of these drugs in normal children, and occasionally in adults, have resulted in transient central nervous system effects. The use of topical P-blockers for treatment of glaucoma has been associated with central nervous system side effects, including depression, fatigue, weakness, confusion, memory loss, headaches, and anxiety. 

Systemic Effects. Systemic cyclopentolate toxicity is dose related and evolves in a manner similar to atropine toxicity. Compared with atropine, however, cyclopentolate causes more CNS effects. 

The answer is c. (Hardman, pp 156-158.) A wide variety of clinical conditions are treated with antimuscarinic drugs. Dicyclomine hydrochloride and methscopolamine bromide are used to reduce Gl motility, although side effects—dryness of the mouth, loss of visual accommodation, and difficulty in urination—may limit their acceptance by patients. Cyclopentolate hydrochloride is used in ophthalmology for its mydriatic and cycloplegic properties during refraction of the eye. Trihexyphenidyl hydrochloride is one of the important antimuscarinic compounds used in the treatment of parkinsonism. For bronchodilation in patients with bronchial asthma and other bronchospastic diseases, ipratropium bromide is used by inhalation. Systemic adverse reactions are low because the actions are largely confined to the mouth and airways. 

Because increased susceptibility to the side effects of cyclopentolate has been reported in infents, yoimg children, and children with spastic paralysis or brain damage, use of concentrations higher than 0.5% is not recommended in these patients. The potential for systemic absorption of cyclopentolate, as of other topically appUed ocular drugs, may be reduced with nasolacrimal occlusion. 

Tropicamide, like atropine, cyclopentolate, and scopolamine, enters the systemic circulation rapidly. After applying two 40-ml drops of 0.5% tropicamide to one eye in eight patients, peak plasma concentrations were reached in 5 to 30 minutes but were variable (1.3 to 5.2 ng/ml).A mean peak concentration of 2.8 ng/ml was measured at 5 minutes. Despite the rapid systemic absorption, tropicamide has a low affinity for systemic muscarinic receptors.Thus adverse systemic reactions to tropicamide are quite rare. Two studies observed no significant adverse reactions associated with the use of tropicamide in 3,851 drug applications in patients undergoing ophthalmoscopy with either 0.5% or 1% tropicamide.The only reported effects were mild and transient transient changes in lOP on the order of 4 to 12 mm occurred in seven patients, and one individual experienced a transient intermittent esotropia. 

To facilitate the application of mydriatics in neonates and infants, a single-instillation solution may be prepared by combining 3.75 ml cyclopentolate 2% with 7.5 ml tropicamide 1% and 3.75 ml phenylephrine 10%.The final solution contains 0.5% cyclopentolate, 0.5% tropicamide, and 2.5% phenylephrine.This combination produces no major side effects and provides an effective pupillary dilation. Alternatively, equal amounts of 1% tropicamide and 2.5% phenylephrine may be mixed together to yield a single combination solution with final concentrations of 0.5% tropicamide and 1.25% phenylephrine. This too should produce adequate pupillary dilation with no major side effects. Again, these solutions can also be applied as a spray. Cyclopentolate, tropicamide, and phenylephrine administered in microdrops (mean drop volume, 5.6 micro liters, as opposed to commercially available standard drops) have the same efficacy with a decreased risk for systemic side effects. 

The effect of antimuscarinic agents on the eye is mydriasis, cycloplegia and reduction of lacrimal secretions. These effects are desirable in ophthalmic examination of non-compliant patients (e.g. children) but considered to be side effects (blurred vision, dry [sandy] eye) in the systemic use of these agents. Cyclopentolate and tropicamide... 

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