Phenylephrine side effects

Mecfianism of Action Phenylephrine HCl is an alpha-receptor sympathetic agonist used in local ocular disorders because of its vasoconstrictor and mydriatic action. It exhibits rapid and moderately prolonged action, and it produces little rebound vasodilatation. Systemic side effects are uncommon. Therapeutic Effect Vasoconstriction and pupil dilation. 

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. 

Based on data submitted to the National Registry of Drug-Induced Ocular Side Effects and those acquired by other investigators, the following guidelines for the clinical use of 10% phenylephrine are suggested ... 

Brown MM, Brown GC, Spaeth GL. Lack of side effects from topically administered 10% phenylephrine eyedrops. Arch Ophthalmol 1980 98 487-488. 

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. 

Hempel S, Senn P, Pakdaman F, Schmid MK, Suppiger M, Schipper I. Einfluss der Pupillenerweiterung mit Phenylephrin 5% auf das perioperative Kreislaufverhalten. [Perioperative circulatory side effects of topical 5% phenylephrine for mydriasis.] Khn Monatsbl Augenheilkd 1999 215(5) 298-304. 

Clinicians have used both vasoconstrictors and vasodilators in the treatment of priapism. Vasoconstrictors, such as phenylephrine or epinephrine, are thought to work by forcing blood out of the corpus cavernosum into the venous return. Epinephrine use has been associated with increases in heart rate and blood pressure. In one prospective nonrandomized unblinded study, aspiration followed by intrapenile irrigation with epinephrine was effective and well tolerated. In that study, as much blood as possible was aspirated from the corpus cavernosum, and the area was irrigated with a 1 1,000,000 solution of epinephrine. The priapism resolved in 37 of the 39 occasions in which it was nsed. The therapy was well tolerated with no serious immediate or long-term side effects. On two occasions, a small intrapenile hematoma formed after treatment. 

The client should avoid using any over-the-counter sinus and cold medications containing pseudoephedrine and phenylephrine, which may accentuate the side effects of epinephrine. 

Treatment with injections into the corpus caver-nosum of alpha adrenergic receptor agonists after aspiration would be the next therapy after terbutaline. Phenylephrine, 10 cc, which corresponds to a dose of 200 ig, is injected into the penis after aspiration. Frequent blood pressure measurements and preferably ECG monitoring are required throughout, and failure to respond may require a second injection of 200 ig and a final dose of 500 pg. Alternatively, epinephrine can be injected in 1-3-cc boluses up to 10 cc (O Brien et al. 1989). Methylene blue has been shown to be useful as an alternative to alpha agonists, with a mechanism felt to be related to inhibition of cyclic GMP, which in turn inhibits smooth muscle relaxation (Steers and Selby 1991). Intracavernosal injection with 50 mg of methylene blue is followed by aspiration and penile compression for 5 min. Transient penile burning and blue discoloration lasting for about 3 days were the reported side effects (Martinez Portillo et al. 2001). 

They are sometimes used to bring about weight loss, but they can cause chemical dependency. Benzedrine and Neo-Synephrine (phenylephrine) are used in medications to reduce respiratory congestion from colds, hay fever, and asthma. Sometimes, benzedrine is taken to combat the desire to sleep, but it has side effects. Methedrine is used to treat depression and in the illegal form is known as speed or crank. The prefix meth means that there is one more CH3 — group on the nitrogen atom. 

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