Narcissism is a personality disorder and every disorder has a clinical cure.
Indeed, rarcissism is a personality disorder. And it will not be called a disorder if it has no clinical cure. Then again, it does not take a professional psychologist to know how to handle these emotional vampires. If friends and family members properly deal with narcissists, life will become easier to both the narcissist and the people around.
Dealing with narcissism is no different from dealing with addictions. Narcissists are addicted to attention so much that they will feel ill without it. Addiction, in general, is cured by a gradual reduction of supply. At first, give the attention that the narcissist needs then reduce it little by little.
Addiction to dangerous elements requires total elimination of the supply. Attention, however, is not a dangerous element but an emotional necessity. Keep gradually reducing the attention given to the narcissist until the attention is balanced. Also, unlike dealing with addiction to dangerous elements, narcissists must not be aware of it.