Information Extraction (IE) from medical texts aims at the automatic recognition of entities and relations of interests. IE is based on shallow analysis and considers only sentences containing important words. Thus IE of drugs from discharge letters can identify as 'current' some past or future medication events. This article presents heuristic observations enabling to filter drugs that are taken by the patients during the hospitalization. These heuristics are based on the default PR structure and linguistic expressions signaling temporal and conditional markers. They are integrated in a system for drug extraction from hospital Patient Records (PRs) in Bulgarian language. Present evaluation results are summarized as well.