Does competitive gaming have anti-doping regulations?

Doping is a big issue in competitive sports such as baseball, cycling, etc. As such, sports athletes must complete drug tests and risk disqualification (or worse) if they are discovered to be using drugs. However, some exemptions are made with regards to prescribed medication for specific conditions.

Does competitive gaming, or eSports, follow the same guidelines? Do these tournaments have the same anti-doping regulations along with exemptions for extenuating circumstances such as medical conditions?

It depends. While most of the competitive gaming leagues I checked out don't mention anything about drug testing explicitly, the International eSports Federation (IeSF) has partnered with the World Anti-doping Agency (WADA), prohibiting a whole standardized myriad of performance-enhancing drugs, testing winners and random other players for them. There is a process through the World Anti-doping Agency for exemptions, which essentially requires the WADA to explicitly approve of someone using a drug in competition because they have a medical condition.

There is a very strict process for therapeutic exemptions, however. A TUE is granted if and only if an athlete absolutely needs to take the prohibited substance for medical reasons, the prohibited substance doesn't provide any additional enhancement of performance other than what would be expected by an athlete returning to normal health, there is no alternative, and the necessity of use isn't a consequence of dependence. Adderall, typically associated with performance enhancement for video games, does not meet any of these criteria.

Other leagues have rules governing showing up to events intoxicated or clearly under the influence of drugs, if not explicitly, in the "tournament officials reserve the right to disqualify any player at any time for any reason" clause.

The most obvious answer to this query is "It depends". Each event has its own rules and most (if not all) events have a proviso about having the rights to make judgement calls about a given event even if it falls outside the scope of the provided rules.

That said, the best approach would be to scrutinize the rules behind some of the most renowned LAN events. Dreamhack's relevant ruling regarding drugs is as such:

1.4 Alcohol and drugs in any form do not belong and are not allowed to be taken onto DreamHack premises. People intoxicated and/or under the influence of drugs/other non-allowed substances will not be allowed on the premises, at any time. People found intoxicated and/or on drugs will be shown off the premises. Smoking is strictly forbidden indoors and is only allowed in designated area outside. Electronic cigarettes is not allowed to use inside of DreamHack.

Nothing in the rules as written directly addresses penalties or other actions levied against players specifically, though this does speak to a firm "no, don't do it" attitude at the event. Furthermore, this does not address paraphernalia, under which a crack pipe, bong, etc. would fall by most peoples' definition. Nothing in the rules as written provides a definite answer with regard to drug paraphernalia, but an educated reading in tandem with the "we reserve the rights to have final say in any situation not addressed by the rules" proviso leads me to believe that the right call is to leave that stuff in the hotel room.

No mention of prescription medication is made anywhere within its rules, and as such it is assumed from a prima facie reading that this rule is intended primarily for the prohibition of "overtly intoxicated" behavior more than any animus towards medication or drugs in general. Much like a lack of mention of prescription medication, no mention of testing or penalties aside from eviction from the event (presumably temporarily) is made in any of the rules as they apply to competitors at Dreamhack's various tournaments.

A cursory reading of the player-specific rules of most LAN tournaments, such as Starladder and others, is roughly similar, and alludes such that the same mindset is likely applicable elsewhere.