What is the statute of limitations on criminal warrants in Maryland?

It will depend on the location and the level of the drug charge. For a felony there may be no limit. For a misdemeanor it would be something fairly short, say 2 or 3 years. But it can be tolled for certain reasons as well.

Also: Because the question states "criminal" drug possession you may also be facing

possible federal charges as well, for which there is no SOL.