| Orphenadrine H1-Antihistamine Blood Vessel Constriction Action Pathway |  | Drug Action | Arginine / Citrulline / Sapropterin / Nitric Oxide / Orphenadrine / Calcium / Magnesium cation / Mesoheme / Flavin adenine dinucleotide / Flavin mononucleotide |
| Orphenadrine H1-Antihistamine Immune Response Action Pathway |  | Drug Action | Orphenadrine / Calcium |
| Orphenadrine NMDA Antagonist Action Pathway |  | Drug Action | L-Glutamine / Glutamic acid / Orphenadrine / Calcium |
| Oseltamivir Action Pathway |  | Drug Action | Oseltamivir / Calcium |
| Osilodrostat Drug Metabolism |  | Metabolic | Osilodrostat |
| Oteracil Drug Metabolism |  | Metabolic | Oteracil |
| Oteseconazole Action Pathway |  | Drug Action | Formic acid / Mesoheme / Ergosterol / Oteseconazole |
| Oxaliplatin Drug Metabolism |  | Metabolic | Oxaliplatin |
| Oxamniquine Predicted Metabolism Pathway |  | Metabolic | Oxamniquine / Mesoheme |
| Oxandrolone Drug Metabolism |  | Metabolic | Oxandrolone |
| Oxaprozin Action Pathway |  | Drug Action | Glutamic acid / Glutathione / Dinoprostone / Oxaprozin / Calcium / Magnesium cation / Zinc / Prostaglandin D2 / Mesoheme / Prostaglandin G2 / Arachidonic Acid |
| Oxaprozin NSAID Action Pathway |  | Drug Action | Glutathione / Dinoprostone / Oxaprozin / Calcium / Mesoheme / Prostaglandin G2 / Arachidonic Acid |
| Oxatomide H1 Antihistamine Smooth Muscle Relaxation Action Pathway |  | Drug Action | Calcium / Magnesium cation / Oxatomide |
| Oxatomide H1-Antihistamine Action |  | Drug Action | Calcium / Oxatomide |
| Oxatomide H1-Antihistamine Blood Vessel Constriction Action Pathway |  | Drug Action | Arginine / Citrulline / Sapropterin / Nitric Oxide / Calcium / Magnesium cation / Mesoheme / Flavin adenine dinucleotide / Flavin mononucleotide / Oxatomide |
| Oxatomide H1-Antihistamine Immune Response Action Pathway |  | Drug Action | Calcium / Oxatomide |
| Oxazepam Action Pathway |  | Drug Action | Pyridoxal phosphate / Glutamic acid / ATP / Oxazepam / Calcium / Magnesium cation / Cyclic adenosine monophosphate / gamma-Aminobutyric acid / Pyrophosphoric acid |
| Oxcarbazepine Action Pathway (New) |  | Drug Action | Oxcarbazepine / Potassium cation / Calcium |
| Oxiconazole Action Pathway |  | Drug Action | Oxiconazole / Formic acid / Mesoheme / Ergosterol |
| Oxiconazole Drug Metabolism |  | Metabolic | Oxiconazole |
| Oxidation of Branched-Chain Fatty Acids |  | Metabolic | Ascorbic acid / Succinic acid / ATP / Levocarnitine / Magnesium cation / Iron / Oxogluric acid / Pyrophosphoric acid |
| Oxidronic acid Drug Metabolism |  | Metabolic | Oxidronic acid |
| Oxomemazine H1-Antihistamine Action |  | Drug Action | Calcium / Oxomemazine |
| Oxprenolol Action Pathway |  | Drug Action | ATP / Potassium cation / Calcium / Oxprenolol |
| Oxprenolol B1-Adrenergic Cardiac Muscle Relaxation Action Pathway |  | Drug Action | ATP / Calcium / Oxprenolol |