Phenylpropanolamine Aminophylline

Amphetamine and cocaine also increase noradrenaline release and a number of drugs with mainly noradrenergic actions can also cause a hyperactive delirium. These include ephedrine, phenylpropanolamine, aminophylline, maprotiline and monoamine oxidase inhibitors (Hollister, 1986). 

Clinically important, potentially hazardous interactions with alprazolam, aminophylline, amphetamines, astemizole, dextroamphetamine, diethylpropion, duloxetine, isocarboxazid, linezolid, MAO inhibitors, mazindol, methadone, methamphetamine, phendimetrazine, phenelzine, phentermine, phenylpropanolamine, pseudoephedrine, ramelteon, ropivacaine, selegiline, sibutramine, St John s wort, sumatriptan, sympathomimetics, tacrine, tizanidine, tramadol, tranylcypromine, trazodone, troleandomycin, tryptophan, zolmitriptan... 

In 8 healthy subjects a single 150-mg oral dose of phenylpropanolamine decreased the clearance of theophylline (given as a single 4-mg/kg intravenous dose of aminophylline 1 hour after the phenylpropanolamine) by 50%. Such a large reduction in clearance would be expeeted to result in some increase in serum theophylline levels, but so far no studies of this potentially clinically important interaction seem to have been earried out in patients. Be alert for evidence of toxicity if both drugs are used. More study is needed. See also Pseudoephedrine and related drugs + Caffeine , p.1276. 

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