Phenylephrine ocular applications

Systemic reactions to 2.5% phenylephrine after topical ocular application to an intact eye have rarely been reported in adults. However, an acute rise in systolic blood pressure occurred in a 1-year-old child after the instillation of 0.5 ml of 2.5% phenylephrine during nasolacrimal duct probing. 

Phenylephrine is seldom given systemically but is still commonly used as a mydriatic for both diagnostic and therapeutic purposes. Ocular application of phenylephrine 10% in pledget form is used to produce hemostasis in laser-assisted in-situ keratomileusis (LASIK) surgery and other ophthalmic surgical procedures. Phenylephrine is in some countries available in a non-prescription concentration of 0.12% for use as an ocular decongestant. Phenylephrine (up to 10 mg intramuscularly) has similar properties and uses to other alpha-adrenoceptor agonists. 

Systemic Effects. Ocular administration of phenylephrine has been reported to induce acute hypertension (see Table 8-2). Sixty patients were studied after three applications of the 10% solution in each eye at 10-minute intervals.Thirty minutes after the last drop, systolic elevations of 10 to 40 mm Hg and diastolic elevations of 10 to 30 mm Hg occurred in all subjects. In each case pulse rate decreased 10 to 20 beats per minute. In contrast to these observations, however, other investigators reported a lack of systemic vasopressor response with the 10% concentration. 

Data collected by the National Registry of Drug-Induced Ocular Side Effects suggest that, in the general population, a group of patients may have certain risk factors for side effects from topical ocular 10% phenylephrine. Of 15 patients with myocardial infercts, 11 died after topical application of 10% phenylephrine. The average age of these patients was 71 years, and nine individuals had a history of cardiovascular disease. 

The synthetic adrenergic agonists—phenylephrine, naphazoline, oxymetazoline, and tetrahydrozoline—are available as ocular decongestants (Table 13-2). After topical application to the eye, constriction of conjimcti-val blood vessels occurs at drug concentration levels that generally do not cause pupillary dilation. These agents provide only palliative therapy, because they have no effect on the conjimctival response to antigen. 

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See also in sourсe #XX -- [ ]

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