Source: Medicines & Healthcare Products Regulatory Agency (GB) Revision Year: 2015 Publisher: The Boots Company PLC, Nottingham, NG2 3AA Trading as: BCM
Phenylephrine is a sympathomimetic agent with mainly direct effects on adrenergic receptors. It has predominantly alpha adrenergic activity and is without stimulating effects on the central nervous system. The sympathomimetic effect of phenylephrine produces vasoconstriction which in turn relieves nasal congestion.
Phenylephrine is readily absorbed after oral administration but is subject to extensive presystemic metabolism, much of which occurs in the enterocytes. As a consequence, systemic bioavailability is only about 40%. Following oral administration, peak plasma concentrations are achieved in 1-2 hours. The mean plasma half life is in the range 2-3 hours. Penetration into the brain appears to be minimal.
Following absorption, the drug is extensively metabolised in the liver. Both phenylephrine and its metabolites are excreted in the urine.
The volume of distribution is between 200 and 500 litres, but there are no data on the extent of plasma protein binding.
There are no preclinical data of relevance to the prescriber which are additional to that already included in other sections of the SPC.
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