That's actually a really thoughtful question that shows you're thinking analytically about addiction - and you're not entirely off base with your reasoning!
You're right that nicotine replacement therapy (patches, gum, etc.) works by providing the addictive substance (nicotine) in a controlled, less harmful way. The key difference is delivery method - cigarettes give you nicotine plus a rapid "hit" that reinforces the addiction cycle, while patches provide steady levels without that reinforcing spike.
However, sexual addiction is neurochemically more complex than nicotine addiction. It's not just about one chemical like dopamine - it involves multiple neurotransmitter systems (dopamine, serotonin, oxytocin, endorphins) working together in intricate ways. More importantly, it's the process and experience that creates the addictive cycle, not just the chemical reward.
There actually are some medications that affect these brain systems - things like SSRIs that modulate serotonin, or naltrexone which blocks opioid receptors - and they're sometimes used to help with compulsive sexual behaviors. But they're not "replacement therapy" in the same way nicotine patches are.
The deeper issue is that sexual addiction often involves psychological components - escapism, emotional regulation, trauma responses - that can't be addressed with a simple chemical substitute. That's why the most effective approaches tend to be behavioral, therapeutic, and spiritual rather than purely pharmaceutical.
Your analytical thinking is spot-on though - you're just dealing with a more complex system than nicotine addiction!