Brown, Houston's first-round draft pick in 2008, said he "unknowingly took a supplement tainted with a banned substance." He would not identify the supplement, but acknowledged that he was "naive" for even trying it.
"Definitely not worth it at all," Brown said. "I didn't gain anything out of it, and I lost a lot. Definitely a life lesson."
The Texans (4-2) have a bye this week and went through a light morning workout on Tuesday. Coach Gary Kubiak expects Brown to start Houston's next game, at Indianapolis on Nov. 1.
Brown is the second Texan to return from a four-game suspension this season for violating the league's policy on performance-enhancing substances. Linebacker Brian Cushing sat out the first four games after a positive test for HCG. Cushing says he never took the drug, and said its presence in his body was the result of "overtrained athlete syndrome."
Brown said Cushing offered helpful advice during his suspension.
"He said it would definitely make me a stronger person," Brown said. "He told me when I came back, be ready to go and the team was doing good and just be able to pick up where we left off and be ready to go forward. That's something that really helped me out."
Brown stayed in Houston during his suspension, and worked out six times a week with a personal trainer. He watched all four games he sat out, and agonized over the time he was missing with his team.
"It was devastating," Brown said. "You get used to coming in here every day and practicing. You kind of take that for granted."
Brown said he also worried about the damage he caused to his own reputation. He hopes that he become a poster child in the Texans' locker room for the risks of using performance-enhancing substances.
"We're all responsible. This is our profession," Brown said. "Anything you put in your body, you have to make sure it follows the NFL guidelines. I was being a little bit naive, and it got me.
"I haven't really been into supplements in my professional career, or even my collegiate career," said Brown, who played at Virginia Tech. "I didn't want to let my teammates down. I let my fans down and my family down. I feel like this is my chance to redeem myself."
Brown made 34 consecutive starts before he was suspended. He said he needs to brush up on his fundamentals this week and said the bye helps him, even though the team won't practice in pads again until Monday.
"I'm sure some people will get away for this bye week," he said. "I'll be here, working on my body and getting my techniques back and making my movements more fluid."
Rashad Butler started at left tackle in Brown's absence, and held his own against two of the league's top pass rushers, Dallas' DeMarcus Ware and the New York Giants' Osi Umenyiora.
The Texans have allowed 16 sacks this season, but Kubiak praised Butler's work. Butler has never started a game in five seasons before taking over Brown's spot in the Sept. 26 game against the Cowboys.
"He helped himself as a pro," Kubiak said. "He went in there and I think he did a good job. He can always do better. Our football team was still able to function offensively and we didn't have to game plan everything to go help him on a regular basis, so I'm proud of the job he did."