The tired guy (listed in the credits as Molnar) was one of the clinic patients in the episode Pilot that thought he had Chronic fatigue syndrome or fibromyalgia.
He came into the clinic claiming that he thought he had chronic fatigue syndrome or fibromyalgia because he was tired a lot more than usual. House realized that he was just a hypochondriac so he decided to give him placebo treatment. He went to the pharmacy and got some Vicodin, then he emptied the bottle got change for a dollar and went to the candy machine and got a bunch of mints. He put the mints in the Vicodin bottle and gave them to the clinic patient. Later on in the episode, he came back looking for a refill.