The main and absolute contraindication to using<unk>  is the concurrent use of adrenergic receptor antagonists; combined, they cause a severe drop in blood pressure and fainting. Alcohol causes an increased frequency of orthostatic hypotension (a sudden drop in blood pressure when getting up), and can also increase the chances of pneumonia and heart attacks. Dopamine antagonists, by their nature of competing for sites at dopamine receptors, reduce the effectiveness of the agonistic<unk> . IV administration of<unk>  is highly discouraged, as it can crystallize in the veins and create a blood clot (thrombus) and block a pulmonary artery (pulmonary embolism).
Apomorphine
Desomorphine
Tripelennamine
Droperidol
Tropisetron
Amfepramone
Benzatropine
Bremazocine