| Olmesartan Action Pathway |  | Drug Action | Olmesartan / Potassium cation / Zinc |
| Olmesartan ARB Action Pathway |  | Drug Action | Glutamic acid / Olmesartan / Zinc |
| Olodaterol Action Pathway |  | Drug Action | ATP / Potassium cation / Calcium / Magnesium cation / Cyclic adenosine monophosphate / Olodaterol |
| Olopatadine H1 Antihistamine Smooth Muscle Relaxation Action Pathway |  | Drug Action | Olopatadine / Calcium / Magnesium cation |
| Olopatadine H1-Antihistamine Action |  | Drug Action | Olopatadine / Calcium |
| Olopatadine H1-Antihistamine Blood Vessel Constriction Action Pathway |  | Drug Action | Arginine / Citrulline / Sapropterin / Nitric Oxide / Olopatadine / Calcium / Magnesium cation / Mesoheme / Flavin adenine dinucleotide / Flavin mononucleotide |
| Olopatadine H1-Antihistamine Immune Response Action Pathway |  | Drug Action | Olopatadine / Calcium |
| Olopatadine Predicted Metabolism Pathway |  | Metabolic | Olopatadine / Mesoheme |
| Olsalazine Action Pathway |  | Drug Action | Glutathione / Mesalazine / Dinoprostone / Olsalazine / Calcium / Mesoheme / Prostaglandin G2 / Arachidonic Acid |
| Omadacycline Action Pathway |  | Drug Action | Omadacycline |
| Omadacycline Predicted Metabolism Pathway |  | Metabolic | Mesoheme / Omadacycline |
| Ombitasvir Action Pathway |  | Drug Action | Magnesium cation / Zinc / Ombitasvir |
| Omeprazole Action Pathway |  | Drug Action | Omeprazole / Potassium cation / Zinc |
| Omeprazole Action Pathway (old) |  | Drug Action | ATP / Omeprazole / Potassium cation / Zinc / Acetylcholine |
| Omeprazole Metabolism Pathway (old) |  | Drug Metabolism | Omeprazole |
| Ondansetron Predicted Metabolism Pathway |  | Metabolic | Ondansetron / Mesoheme |
| Ondansetron Serotonin antagonist Action Pathway |  | Drug Action | Pyridoxal phosphate / Tryptophan / Sapropterin / Ondansetron / Calcium / Iron / Oxitriptan |
| Orciprenaline Action Pathway |  | Drug Action | ATP / Orciprenaline / Potassium cation / Calcium / Magnesium cation / Cyclic adenosine monophosphate |
| Orciprenaline Predicted Metabolism Pathway |  | Metabolic | Orciprenaline / Mesoheme |
| Ornithine Aminotransferase Deficiency (OAT Deficiency) |  | Disease | Pyridoxal phosphate / Ademetionine / Arginine / Aspartic acid / Ornithine / Adenosine phosphate / Succinic acid / Glutamic acid / Glycine / Creatine / Citrulline / NADH / ATP / Proline / Sapropterin / Nitric Oxide / Mesoheme / Glycocyamine / 3,4-Dihydro-2h-Pyrrolium-5-Carboxylate / Oxogluric acid / N(5)-[(hydroxyamino)(imino)methyl]-L-ornithine / Flavin adenine dinucleotide / Flavin mononucleotide / Urea / Pyrophosphoric acid / Maleic acid / 4-Carboxy-4-Aminobutanal |
| Ornithine Aminotransferase Deficiency (OAT Deficiency) |  | Disease | Pyridoxal phosphate / Ademetionine / Arginine / Aspartic acid / Ornithine / Adenosine phosphate / Succinic acid / Glutamic acid / Glycine / Creatine / Citrulline / NADH / ATP / Proline / Sapropterin / Nitric Oxide / Mesoheme / Glycocyamine / 3,4-Dihydro-2h-Pyrrolium-5-Carboxylate / Oxogluric acid / N(5)-[(hydroxyamino)(imino)methyl]-L-ornithine / Flavin adenine dinucleotide / Flavin mononucleotide / Urea / Pyrophosphoric acid / Maleic acid / 4-Carboxy-4-Aminobutanal |
| Ornithine Transcarbamylase Deficiency (OTC Deficiency) |  | Disease | Pyridoxal phosphate / Pyruvic acid / Arginine / Aspartic acid / Ornithine / L-Glutamine / Adenosine phosphate / Glutamic acid / Citrulline / NADH / Alanine / ATP / Calcium / Oxogluric acid / Urea / Pyrophosphoric acid / Maleic acid |
| Ornithine Transcarbamylase Deficiency (OTC Deficiency) |  | Disease | Pyridoxal phosphate / Pyruvic acid / Arginine / Aspartic acid / Ornithine / L-Glutamine / Adenosine phosphate / Glutamic acid / Citrulline / NADH / Alanine / ATP / Calcium / Oxogluric acid / Urea / Pyrophosphoric acid / Maleic acid |
| Orphenadrine Drug Action |  | Drug Action | Orphenadrine / Calcium |
| Orphenadrine H1 Antihistamine Smooth Muscle Relaxation Action Pathway |  | Drug Action | Orphenadrine / Calcium / Magnesium cation |