indication

For the treatment of nasal congestion, control of urinary incontinence, priapism and obesity.

pharmacology

Phenylpropanolamine (PPA), a sympathomimetic agent structurally similar to pseudoephedrine, is used to treat nasal congestion. Phenylpropanolamine is found in appetite suppressant formulations and with guaifenesinin in cough-cold formulations. In 2000, the FDA requested that all drug companies discontinue marketing products containing phenylpropanolamine, due to an increased risk of hemorrhagic stroke in women who used phenylpropanolamine.

mechanism of action

Phenylpropanolamine acts directly on alpha- and, to a lesser degree, beta-adrenergic receptors in the mucosa of the respiratory tract. Stimulation of alpha-adrenergic receptors produces vasoconstriction, reduces tissue hyperemia, edema, and nasal congestion, and increases nasal airway patency. PPA indirectly stimulates beta-receptors, producing tachycardia and a positive inotropic effect.

toxicity

May induce ventricular extrasystoles and short paroxysms of ventricular tachycardia, a sensation of fullness in the head and tingling of the extremities; LD₅₀=1490mg/kg (orally in rat)

biotransformation

Hepatic

absorption

Reduced bioavailability (about 38%) from gastrointestinal tract because of first pass metabolism by monoamine oxidase in the stomach and liver.

half life

2.1 to 3.4 hours.

drug interactions

Acetophenazine: Decreased anorexic effect, may increase psychotic symptoms

Alseroxylon: Increased arterial pressure

Amitriptyline: The tricyclic antidepressant, amitriptyline, increases the sympathomimetic effect of phenylpropanolamine.

Amoxapine: The tricyclic antidepressant, amoxapine, increases the sympathomimetic effect of phenylpropanolamine.

Bromocriptine: The sympathomimetic, phenylpropanolamine, increases the toxicity of bromocriptine.

Chlorpromazine: Decreased anorexic effect, may increase psychotic symptoms

Clomipramine: The tricyclic antidepressant, clomipramine, increases the sympathomimetic effect of phenylpropanolamine.

Deserpidine: Increased arterial pressure

Desipramine: The tricyclic antidepressant, desipramine, increases the sympathomimetic effect of phenylpropanolamine.

Doxepin: The tricyclic antidepressant, doxepin, increases the sympathomimetic effect of phenylpropanolamine.

Ethopropazine: Decreased anorexic effect, may increase psychotic symptoms

Fluoxetine: Risk of serotoninergic syndrome

Fluphenazine: Decreased anorexic effect, may increase psychotic symptoms

Fluvoxamine: Risk of serotoninergic syndrome

Guanethidine: Phenylpropanolamine may decrease the effect of guanethidine.

Imipramine: The tricyclic antidepressant, imipramine, increases the sympathomimetic effect of phenylpropanolamine.

Isocarboxazid: Increased arterial pressure

Linezolid: Possible increase of arterial pressure

Mesoridazine: Decreased anorexic effect, may increase psychotic symptoms

Methdilazine: Decreased anorexic effect, may increase psychotic symptoms

Methotrimeprazine: Decreased anorexic effect, may increase psychotic symptoms

Methyldopa: Increased arterial pressure

Midodrine: Increased arterial pressure

Moclobemide: Moclobemide increases the sympathomimetic effect of phenylpropanolamine.

Nortriptyline: The tricyclic antidepressant, nortriptyline, increases the sympathomimetic effect of phenylpropanolamine.

Pargyline: Increased arterial pressure

Paroxetine: Risk of serotoninergic syndrome

Perphenazine: Decreased anorexic effect, may increase psychotic symptoms

Phenelzine: Increased arterial pressure

Prochlorperazine: Decreased anorexic effect, may increase psychotic symptoms.

Promazine: Decreased anorexic effect, may increase psychotic symptoms

Promethazine: Decreased anorexic effect, may increase psychotic symptoms.

Propericiazine: Decreased anorexic effect, may increase psychotic symptoms.

Propiomazine: Decreased anorexic effect, may increase psychotic symptoms

Protriptyline: The tricyclic antidepressant, protriptyline, increases the sympathomimetic effect of phenylpropanolamine.

Rasagiline: Increased arterial pressure

Reserpine: Increased arterial pressure

Thiethylperazine: Decreased anorexic effect, may increase psychotic symptoms

Thioridazine: Decreased anorexic effect, may increase psychotic symptoms

Tranylcypromine: Increased arterial pressure

Trifluoperazine: Decreased anorexic effect, may increase psychotic symptoms

Triflupromazine: Decreased anorexic effect, may increase psychotic symptoms

Trimeprazine: Decreased anorexic effect, may increase psychotic symptoms

Trimipramine: The tricyclic antidepressant, trimipramine, increases the sympathomimetic effect of phenylpropanolamine.

Venlafaxine: Risk of serotoninergic syndrome