This value set has an inline code system http://hl7.org/fhir/v3/substanceAdminSubstitution, which defines the following codes:
| Lvl | Code | Display | Definition | 
| 1 | _ActSubstanceAdminSubstitutionCode  | ActSubstanceAdminSubstitutionCode | Description: Substitution occurred or is permitted with another product that may potentially have different ingredients, but having the same biological and therapeutic effects. | 
| 2 |   E  | equivalent | Description: Substitution occurred or is permitted with another bioequivalent and therapeutically equivalent product. | 
| 3 |     EC  | equivalent composition | Description: 
                         
                        Substitution occurred or is permitted with another product that is a: 
                        
                           pharmaceutical alternative containing the same active ingredient but is formulated with different salt, ester
                           pharmaceutical equivalent that has the same active ingredient, strength, dosage form and route of administration
                        
                        
                           Examples: 
                         
                        
                           
                              Pharmaceutical alternative: Erythromycin Ethylsuccinate for Erythromycin Stearate
                           
                              Pharmaceutical equivalent: Lisonpril for Zestril | 
| 4 |       BC  | brand composition | Description: 
                         
                        Substitution occurred or is permitted between equivalent Brands but not Generics 
                        
                           Examples: 
                         
                        
                           Zestril  for Prinivil
                           Coumadin for Jantoven | 
| 4 |       G  | generic composition | Description: Substitution occurred or is permitted between equivalent Generics but not Brands 
                        
                           Examples: 
                         
                        
                           Lisnopril (Lupin Corp) for Lisnopril (Wockhardt Corp) | 
| 3 |     TE  | therapeutic alternative | Description: Substitution occurred or is permitted with another product having the same therapeutic objective and safety profile. 
                        
                           Examples: 
                         
                        
                           ranitidine for Tagamet | 
| 4 |       TB  | therapeutic brand | Description: Substitution occurred or is permitted between therapeutically equivalent Brands but not Generics >
                           Examples: 
                         
                        
                           Zantac for Tagamet | 
| 4 |       TG  | therapeutic generic | Description: Substitution occurred or is permitted between therapeutically equivalent Generics but not Brands >
                           Examples: 
                         
                        
                           Ranitidine  for cimetidine | 
| 2 |   F  | formulary | Description: This substitution was performed or is permitted based on formulary guidelines. | 
| 2 |   N  | none | No substitution occurred or is permitted. |