Phenylephrine pharmacokinetics

Pharmacokinetics Phenylephrine is irregularly absorbed from and readily metabolized in the GI tract. After IV administration, a pressor effect occurs almost immediately and persists for 15-20 minutes. After IM administration, a pressor effect occurs within 10-15 minutes and persists for 50 minutes to 1 hour. After oral inhalation of phenylephrine in combination with isoproterenol, pulmonary effects occur within a few minutes and persist for about 3 hours. The pharmacologic effects of phenylephrine are terminated at least partially bythe uptake of the drug into the tissues. Phenylephrine is metabolized in the liver and intestine by the enzyme monoamine oxidase (MAO). The metabolites and their route and rate of excretion have not been identified. 

Chien DS, Schoenwald RD. Ocular pharmacokinetics and pharmacodynamics of phenylephrine and phenylephrine oxazoli-dine in rabbit eyes. Pharm Res 1990 7 476-483. 

Hypotension not responsive to intravenous fluids should be managed with vasopressors, such as dopamine, norepinephrine, epinephrine, and/or phenylephrine. If seizures occur, benzodiazepines should be administered. Due to their pharmacokinetic characteristics, moderate volume of distribution, and low protein binding, procainamide and NAPA may be removed via hemodialysis and hemoperfu-sion. Both procainamide and NAPA serum concentrations should be obtained. Normal therapeutic ranges are procainamide, 3-14pgml NAPA, 12-35 pg ml Measurement of electrolytes, renal function tests, and arterial blood gases should be considered. 

Example Pseudoephedrine hydrochloride (Actifed, Sudafed), phenylpropanolamine (Allerest, Dimetapp), phenylephrine HCK (Neo-Synephrine, Sinex), and pseudoephedrine (Actifed, Sudafed) frequently combined with an antihistamine, analgesic, or antitussive (anticough) in oral cold remedies Route Tablet, capsule, liquid Pregnancy category C Pharmacokinetic Absorbed by the GI tract, metabolized in liver and excreted in urine. Not removed by hemodialysis... 

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