Antidepressant pill. Finger holding a tablet of amitriptyline. Amitriptyline is a member of the tricyclic antidepressant (TCA) group of drugs. These work by increasing the levels of the neurotransmitters serotonin and norepinephrine in the brain. Amitriptyline is also used to treat bedwetting and chronic pain. As with many TCAs, it can produce unpleasant side effects, including dry mouth, drowsiness, irregular heartbeat and low blood pressure. Side effects often force the patient to lower their dosage; this 10 milligram tablet is a small dose. TCAs are becoming less popular than selective serotonin reuptake inhibitors, such as Prozac, which are less toxic.