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Level 4
  
R - Respiratory systemR01 - Nasal preparationsR01B - Nasal decongestants for systemic useR01BA - Sympathomimetics
  
R01BA01 - PhenylpropanolamineR01BA02 - PseudoephedrineR01BA03 - PhenylephrineR01BA51 - Phenylpropanolamine, combinationsR01BA52 - Pseudoephedrine, combinationsR01BA53 - Phenylephrine, combinations
  
 
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