Like ephedrine, pseudoephedrine also has an indirect effect by releasing norepinephrine from its storage sites. Also, drainage of sinus secretions is increased, and obstructed eustachian ostia may be opened. Oral administration of pseudoephedrine usually produces negligible effects on blood pressure. Pseudoephedrine may increase irritability of the heart muscle and may affect ventricular conduction, especially with high doses administered to patients with preexisting cardiac disease. Nasal decongestion may persist for 8 hours following oral administration of 60 mg and up to 12 hours following 120 mg of the drug in extended-release capsules.
Pseudoephedrine is presumed to cross the placenta as well as the blood brain barrier.
Pseudoephedrine may also be distributed into breast milk. Pseudoephedrine is incompletely metabolized in the liver to norpseudoephedrine, the primary active metabolite of the parent. The rate of urinary excretion is accelerated upon urinary acidification to a pH near 5. Upon alkalination of the urine to a pH of approximately 8, some of the drug is reabsorbed into the kidney tubule and the rate of urinary excretion is slowed. Since pseudoephedrine is a sympathomimetic and vasoconstrictor, it should be used cautiously in patients with uncontrolled hypertension.