Xanax is a prescription drug of the benzodiazepine class. Because Xanax is a depressant of the neurological system, it has a tranquilizing effect. It is metabolized and eliminated quicker than other benzodiazepines. Its half-life is 12 to 15 hours, and its effects kick in after about 15 minutes. Xanax is FDA-approved for very short-term treatment--up to eight weeks, of panic disorder.

Paradoxical Reactions

According to Robert Chew, a psychiatric-pharmacist specialist in Sacramento, paradoxical reactions occur in 5 to 10 percent of users of benzodiazepines, and they are most often seen in children and elderly individuals. Paradoxical reactions are drug reactions that occur in the absence of the intended reactions. Paradoxical reactions of Xanax include nervousness, aggressiveness, violent behavior, phobias, obsessive-compulsive disorder, suicidal intentions, hallucinations and paranoia. Paradoxical reactions can occur after short-term or long-term use.

Physical Side Effects

Physical side effects of Xanax include dry mouth, respiratory changes, dizziness, confusion, drowsiness, memory loss and ataxia, or slurred speech, according to Dr. Chew. An overdose can lead to somnolence, or extreme sleepiness, hypoventilation, impaired motor functions, fainting, coma and death. Mixing Xanax with alcohol or other neurological depressants can increase the risk of coma and death. Xanax can also cause psychomotor impairment that can result in road accidents, industrial work accidents, falls and fractures. Elderly individuals are at a higher risk of experiencing psychomotor side-effects. All of these effects can occur after short- or long-term use.

Psychological Side Effects

Short- or long-term use of Xanax can lead to personality changes such as narcissistic personality traits, carelessness and hyper-confidence. Jack Gorman, a New York psychiatrist and the author of "The Essential Guide to Psychiatric Drugs," describes these effects as frequently occurring. The explanation is that Xanax has a depressing effect on neurotransmitters in the body, which are involved in producing empathy when others get hurt, and fear in socially or physically threatening situations. When these neurotransmitters are artificially depressed, people are not as worried about real threats or harm done to others.

Tolerance

Tolerance occurs when the dosage originally prescribed no longer generates the initial effects. The risk of tolerance is greater with more potent benzodiazepines, such as Xanax. When people no longer experience the desired effects of the drug, it is tempting to increase the dosage. This quickly can lead to drug dependence. According to Dr. Gorman, addiction to Xanax can be as difficult to quit as addiction to other potent drugs.

Brain Atrophy

According to Peter Breggin, an Ithaca-based psychiatrist and author of "Toxic Psychiatry," long-term use of Xanax and other benzodiazepines can result in cognitive impairment. Breggin makes reference to a letter to the editor in the July 1989 issue of "Archives of General Psychiatry," where Isaac Marks and colleagues cite studies showing that long-term use of small doses of Xanax can lead to an enlargement of the cerebral ventricular, which is a sign of a brain atrophy.