Among patients able to successfully initiate injectable naltrexone, long-term rates were similar  Another concern is that while methadone and buprenorphine patients maintain high drug tolerance in the event of return to street drug use, naltrexone allows tolerance to fade, leading to risk of overdose in people who relapse and thus higher mortality. Guidelines from the World Health Organization cite evidence of superiority in reducing mortality and retaining patients in care with opioid agonists (methadone or buprenorphine), concluding that most patients should be advised to use agonists rather than antagonists like naltrexone.A 2011 review found insufficient evidence to determine the effect of naltrexone taken by mouth in opioid dependence. While some do well with this formulation, it must be taken daily, and a person whose cravings become overwhelming can obtain opioid intoxication simply by skipping a dose. Due to this issue, the usefulness of oral naltrexone in opioid use disorders is limited by the low retention in treatment. Naltrexone by mouth remains an ideal treatment for a small number of people with opioid use, usually those with a stable social situation and motivation. With additional contingency management support, naltrexone may be effective in a broader population. Others
Naltrexone is not useful for quitting smoking. Naltrexone has also been under investigation for reducing behavioral addictions such as gambling or kleptomania as well as compulsive sexual behaviors in both offenders and non-offenders (e.g. compulsive porn viewing and masturbation). The results were promising.
Skin-bleaching products that inhibit pigmentation or cosmetic creams containing the ingredients alpha hydroxy acids or retinoids are known to be effective. Liver spots can also be frozen off with liquid nitrogen; that is, via cryosurgery. See also
Freckle
Lentigo
List of cutaneous conditions

References
External links
 Media related to Solar lentigo at Wikimedia Commons