Complex sentence: It is the active metabolite of phenacetin, once popular as an analgesic and antipyretic in its own right, but unlike phenacetin and its combinations, paracetamol is not considered carcinogenic at therapeutic doses.
Split into simpler sentences: It is the active metabolite of phenacetin, once popular as an analgesic and antipyretic in its own right. However, unlike phenacetin and its combinations, paracetamol is not considered carcinogenic at therapeutic doses.