Phenylephrine adverse effects

The incidence of adverse effects is high with 10% phenylephrine, but less with lower concentrations. Systemic reactions also increase with increased frequency of use and when phenylephrine is applied in a pledget. The package inserts for 10% phenylephrine in the USA and Australia require that the drug should not be used more often than once an hour. A large number of severe... 

The hypertensive and other serious adverse effects of intravenous phenylephrine and phenylephrine absorbed from eye drops can be markedly increased by intravenous or intramuscular atropine. 

Fraunfelder FT, Scafidi AF. Possible adverse effects from topical ocular 10% phenylephrine. AmJ Oph almol (1978) 85, 447-53. 

Lai Y-K. Adverse effect of intraoperative phenylephrine 10% case report. Br J Ophfftalmol... 

Cardiovascular Disease. Patients with systemic hypertension, arteriosclerosis, and other cardiovascular diseases may be at risk when high concentrations of topically administered adrenergic agonists such as phenylephrine are used. Repeated topical doses or soaked cotton pledgets placed in the conjunctival sac have been associated with adverse cardiovascular effects. Likewise, P-blockers should be avoided or used cautiously in patients with congestive heart disease, severe bradycardia, and high-grade atrioventricular block. Topical P-blockers, however, may be used safely in patients with cardiac pacemakers. 

Thyroid Disease. Elevated blood pressure or other adverse cardiovascular effects can result when patients with Graves disease receive adrenergic agonists with vasopressor activity. This is due to the increased catecholamine activity associated with hyperthyroidism. The primary agent to be avoided or used cautiously is topically applied phenylephrine for pupillary dilation. 

Ocular Effects. Local adverse events can include transient pain, lacrimation, and keratitis (see Table 8-2). Phenylephrine eyedrops have also been reported to cause allergic dermatoconjunctivitis, resulting in a scalded appearance aroimd the eye. 

Patients taking certain systemic medications are also more sensitive to the pressor effects of phenylephrine. In individuals taking atropine, the pressor effect of phenylephrine is augmented, and tachycardia can occur. Tricyclic antidepressants and monoamine oxidase (MAO) inhibitors also potentiate the cardiovascular effects of topical phenylephrine. The concomitant use of phenylephrine is contraindicated with these agents, even up to 21 days after cessation of MAO inhibitor therapy. Similarly, patients taking reserpine, guanethidine, or methyldopa are at increased risk for adverse pressor effects from topical phenylephrine because of denervation hypersensitivity accompanying the chemical sympathectomy. 

Because of the premature infent s small body mass and less mature cardiovascular and cerebrovascular status, prudence dictates using the lowest concentration yet the most effective combination of mydriatics for pupillary dilation. A combination of 2.5% phenylephrine and 0.5% to 1.0% tropicamide provides sufficient mydriasis without adverse cardiovascular effects in preterm infents.The use of tropicamide alone, however, does not generally produce a sufficient mydriasis in premature infants. Adding cyclopentolate to the tropicamide regimen improves mydriasis but may contribute to elevated blood pressure and heart rate. Moreover, because of possible gastric secretory inhibition in preterm infants, the concentration of cyclopentolate should be limited to 0.25%. A commercially available combination of 1% phenylephrine and... 

Because of its risk of adverse pressor effects, the 10% concentration of topical phenylephrine should be avoided for pupillary dilation, especially in patients with cardiac disease, systemic hypertension, aneurysms, and advanced arteriosclerosis. However, mild hypertension is not necessarily a contraindication to the use of the 2.5% concentration phenylephrine. 

Fraunfelder FW, Fraunfelder FT, Jensvold B. Adverse systemic effects from pledgets of topical ocular phenylephrine 10%. Am J Ophthalmol 2002 134(4) 624-5. 

Catecholamine vasopressors may result in adverse peripheral vasoconstrictive, metabolic, and dysrhythmogenic effects that limit or outweigh their positive effects on the central circulation. Norepinephrine, phenylephrine, and epinephrine can produce a lactic acidosis secondary to excessive constriction in peripheral arterioles. 

The pressor effects of intravenous infusions of noradrenaline were increased four to eightfold, of adrenaline two to fourfold, and of phenylephrine two to threefold in 4 healthy subjects who had been taking imipramine 75 mg daily for 5 days. There were no noticeable or consistent changes in their response to isoprenaline (isoproterenol). However, in a study of possible adverse interactions between imipramine and isoprenaline, although no abnormalities of heart rhythm were seen, one out of the 4 healthy subjects studied showed potentiation of isoprenaline- induced tachycardia. ... 

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