Patients taking tricyclic antidepressants show a grossly exaggerated response (hy- pertension, cardiac arrhythmias, etc.) to
parenteral noradrenaline (norepinephrine), adrenaline (
epinephrine), and to a lesser extent, to phenylephrine.
It has been suggested that these drugs should be introduced cautiously until the full effects are known. Anecdotal evidence suggests that local anaesthetics containing these vasoconstrictors are commonly used in patients taking tricyclic antidepressants with no problems. However there have been a few case reports of adverse effects occurring during dental treatment. Felypressin may be a safe alternative. The effects of phenylephrine given orally or as nasal drops does not appear to have been studied.