His Addictive Savior by Leo Rivers

Beneath the harsh ER lights, Dr. Samuel Grant discovers an irresistible need: to save young heroin addict Noah Turner and claim him.
Sam tries to resist temptation.
But Noah’s desire for a ‘Daddy’ awakens his craving to dominate a much younger man.
A forbidden connection sparks as they dive into an intoxicating and addictive relationship. Sam’s connection with Noah turns into a seductive power exchange that feeds both their desires.
Until all of that is threatened by Noah’s past. When Noah’s former dealer comes knocking, Sam’s protective instincts roar to life. He becomes his savior, willing to risk his career and his reputation to keep what he’s found.