| Code | Display | Definition |
| anatomical | Anatomical Class | Classification by anatomical main group or body system on which the medication acts (e.g., cardiovascular system, alimentary tract). Codes may be drawn from any suitable coding system, such as the anatomical levels of WHO ATC. |
| therapeutic | Therapeutic Class | Classification based on the therapeutic use of the medication (e.g., antihypertensive, analgesic). |
| pharmacologic | Pharmacologic Class | Classification based on the pharmacologic action of the medication (e.g., beta-blocker, ACE inhibitor). |
| moa | Mechanism of Action | Classification based on the mechanism by which the medication exerts its effect. |
| chemical | Chemical Structure Class | Classification based on the chemical structure of the medication (e.g., benzodiazepine, statin). |
| regulatory | Regulatory Classification | Classification assigned by a regulatory authority (e.g., prescription-only, orphan drug designation, biosimilar status). |
| controlled-substance | Controlled Substance Schedule | Classification under a controlled-substance scheduling scheme (e.g., DEA schedules, narcotic/psychotropic classification). |
| legal-status | Legal/Marketing Status | Classification by legal or marketing status (e.g., prescription-only, over-the-counter, behind-the-counter). |
| reimbursement | Reimbursement/Formulary Class | Classification used for reimbursement or formulary management (e.g., tier, formulary group). |
| essential-medicines | Essential Medicines List | Inclusion on a public-health essential-medicines list (e.g., the WHO Model List of Essential Medicines). |