For example, substances like alcohol and benzodiazepines can involve severe physical withdrawal symptoms while cocaine results in mostly psychological symptoms. Physiological changes caused by cocaine withdrawal include vivid and unpleasant dreams, insomnia, hypersomnia, anger, increased appetite, weight gain, psychomotor retardation, agitation, depression, and anxiety. According to a study done by Gawin and Kleber in 1986, there are three phases in the withdrawal process. They observed the behavior of 30 cocaine-dependent individuals. Phase one, the crash, is characterized by acute dysphoria, irritability and anxiety, increased desire for sleep, exhaustion, increased appetite, decreased craving to use. Phase two, withdrawal, is characterized by increasing craving to use, poor concentration, some irritability and some lethargy, which persisted for up to 10 weeks. Lastly, phase three is characterized by the intermittent craving to use in the context of external cues. Cocaine and its metabolites are eliminated from the body by 3 days. There are not any FDA-approved medications that specifically help treat cocaine withdrawal, however, there are some useful medications that could possibly help individuals overcome their addiction. One example is propranolol. Propranolol is a beta blocker that has been approved to treat hypertension, angina, anxiety, and other related psychological problems. Buprenorphine and naltrexone are two substances that act as an effective treatment in the earlier stages of withdrawal. Pathophysiology
Cocaine pharmacodynamics involve multiple complex mechanisms. Although it has a short half-life (~ 1 hour), cocaine metabolites, which rise in concentrations several hours after cocaine ingestion, persist in circulation for up to 24 hours, and may cause delayed or recurrent coronary vasoconstriction.
Pathology
The histology of lichen nitidus is significant for a "...localized granulomatous lymphohistiocytic infiltrate in an expanded dermal papilla with thinning of overlying epidermis and downward extension of the rete ridges at the lateral margin of the infiltrate, producing a typical claw clutching a ball picture...."

Treatment
Generally, lichen nitidus is asymptomatic and self-limited; therefore, no treatment is required. However, if persistent pruritus is present, or the appearance “...interferes with daily activities or outlook...” topical glucocorticoids may be tried. If the disease process is symptomatic, generalized and extensive, oral glucocorticoids may be indicated. Other reported treatments include PUVA, UVA/UVB phototherapy, astemizole, acitretin, and etretinate. When appears with sun/humidity; air conditioning (cool dry air) reduces swelling and discomfort. History
Felix Pinkus first described the condition in 1907. See also
Lichen planus
List of cutaneous conditions

References
External links

Lichen Nitidus at DermNet photo library