Is masturbation considered prohibited, even once in a lifetime, by analogy with the rule "that which intoxifies in large amounts is also prohibited in small amounts" applied to alcohol?

Prohibited acts share a common origin in legal prohibition and interdiction, even if they differ in rank and gravity of offense. A person who commits a sin once is not equal to one who commits it multiple times. So, whoever masturbates once bears its sin, unless he repents, and his sin is not equal to that of one who does so more than once. For "unto all shall be degrees for what they did. And your Lord is not unaware of what they do."