Having unambiguous standard names for each drug (standardization of drug nomenclature) is important because a drug may be sold by many different brand names, or a branded medication may contain more than one drug. For example, the branded medications Celexa, Celapram and Citrol all contain the same active ingredient: citalopram; and the antibiotic widely known by the brand name Bactrim contains two active ingredients: trimethoprim and sulfamethoxazole. This combination of two antibiotic agents in one tablet has been available as a generic for decades, but the brand names Bactrim and Septra are still in common use.