Antidepressants increase risk of suicidal thinking and behavior in children, adolescents, and young adults (18-24 years of age) with major depressive disorder and other psychiatric disorders. Protriptyline is FDA approved for treatment of depression in adolescents. May aggravate aggressive behavior or worsen psychosis in some patients or precipitate shift to mania or hypomania in bipolar disorder. Monotherapy in bipolar disorder should be avoided. Protriptyline not FDA approved for treatment of bipolar depression. May cause anticholinergic effects (use with caution in decreased gastrointestinal motility, paralytic ileus, urinary retention, benign prostatic hypertrophy, xerostomia, or visual problems). TCAs may rarely cause bone marrow suppression. May cause orthostatic hypotension (use with caution in cerebrovascular disease, cardiovascular disease, hypovolemia, or concurrent medication use which may predispose to hypotension/bradycardia). May cause sedation. Use with caution in history of cardiovascular disease (including previous myocardial infarction, stroke, tachycardia, or conduction abnormalities), in diabetes mellitus (may alter glucose regulation), in hepatic impairment, and in renal impairment. Use with caution in risk of seizures, including patients with history of seizures, head trauma, brain damage, alcoholism, or concurrent therapy with medications which may lower seizure threshold, and in hyperthyroidism or patients receiving thyroid supplementation due to concerns of pro-arrhythmogenesis. Hyperpyrexia observed with TCAs in combination with anticholinergics and/or neuroleptics, particularly during hot weather. Effects may be potentiated when used with other sedative drugs or ethanol. Use with caution in the elderly. Discontinuation recommended prior to elective surgery requiring general anesthesia. Therapy should not be abruptly discontinued in patients receiving high doses for prolonged periods. May increase risks associated with electroconvulsive therapy.