Final answer:
Fluoxetine, also known as Prozac, is the most likely drug to be used in treating OCD and related disorders such as hair pulling and nail biting.
Step-by-step explanation:
The drug that is MOST likely to be used in treating OCD and related disorders such as hair pulling and nail biting is fluoxetine. Fluoxetine, also known as Prozac, is a selective serotonin reuptake inhibitor (SSRI) that increases the levels of serotonin in the central nervous system. SSRIs, including fluoxetine, have been found to be useful in the treatment of obsessive-compulsive disorders.