like methylphenidate (Ritalin, Focalin, Concerta), and amphetamine (Adderall, Attentin, Dexedrine, Vyvanse). ADHD is thought to be caused by an insufficiency of dopamine and norepinephrine activity in the prefrontal cortex of the brain. Most of the TCAs inhibit the reuptake of norepinephrine, though not dopamine, and as a result, they show some efficacy in remedying the disorder. Notably, the TCAs are more effective in treating the behavioral aspects of ADHD than the cognitive deficits, as they help limit hyperactivity and impulsivity, but have little to no benefits on attention. Chronic pain The TCAs show efficacy in the clinical treatment of a number of different types of chronic pain, notably neuralgia or neuropathic pain and fibromyalgia. The precise mechanism of action in explanation of their analgesic efficacy is unclear, but it is thought that they indirectly modulate the opioid system in the brain downstream via serotonergic and noradrenergic neuromodulation, among other properties. They are also effective in migraine prophylaxis, though not in the instant relief of an acute migraine attack. They may also be effective to prevent chronic tension headaches. Side effects Many side effects may be related to the antimuscarinic properties of the TCAs. Such side effects are relatively common and may include dry mouth, dry nose, blurry vision, lowered gastrointestinal motility or constipation, urinary retention, cognitive and/or memory impairment, and increased body temperature. Other side effects may include drowsiness, anxiety, emotional blunting (apathy/anhedonia), confusion, restlessness, dizziness, akathisia, hypersensitivity, changes in appetite and weight, sweating, muscle twitches, weakness, nausea and vomiting, hypotension, tachycardia, and rarely, irregular heart rhythms. Twitching, hallucinations, delirium and coma are also some of the toxic effects caused by overdose. Rhabdomyolysis or muscle breakdown has been rarely reported with this class of drugs as well. Tolerance to these adverse effects of these drugs often develops if treatment is continued. Side effects may also be less troublesome if treatment is initiated with low doses and then gradually increased, although this may also delay the beneficial effects. TCAs can behave like class 1A antiarrhythmics, as such, they can theoretically terminate ventricular fibrillation, decrease cardiac contractility and increase collateral blood circulation to ischemic heart muscle. Naturally, in overdose, they can be cardiotoxic, prolonging heart rhythms and increasing myocardial irritability. New research has also revealed compelling evidence of a link between long-term use of anticholinergic medications like TCAs and dementia. Although many studies have investigated this link, this was the first study