If a patient is taking tricyclic antidepressants, which should be avoided?

• A. Vasoconstrictors
• B. Antibiotics
• C. Antacids
• D. Antihistamines

Answer: (A)

When a patient is taking a tricyclic antidepressant, avoid vasoconstrictors because these drugs can trigger an exaggerated stress response. TCAs block the reuptake of norepinephrine, leaving more of this neurotransmitter available at nerve endings. Vasoconstrictors used in local anesthesia (like epinephrine and related agents) increase catecholamine activity and stimulate adrenergic receptors. Put together, the combination can cause a dangerous rise in blood pressure and heart rate, with risk of arrhythmias or myocardial ischemia, especially in those with underlying heart problems. Other drug classes may have interactions, but the risk with vasoconstrictors is the most clinically significant in this context.