| Ranitidine H2 Anti-Histamine Action Pathway |  | Drug Action | ATP / Ranitidine / Potassium cation / Magnesium cation / Zinc / Cyclic adenosine monophosphate |
| Ranolazine Action Pathway |  | Drug Action | Ranolazine / Potassium cation / Calcium / Cyclic adenosine monophosphate |
| Rapacuronium Predicted Metabolism Pathway |  | Metabolic | Mesoheme / Rapacuronium |
| Ras Signaling Pathway |  | Signaling | Magnesium cation / Zinc |
| Rasagiline Action Pathway |  | Drug Action | Pyridoxal phosphate / Ademetionine / Tyrosine / ATP / Sapropterin / Dopamine / Levodopa / Rasagiline / Magnesium cation / Iron / Cyclic adenosine monophosphate / Flavin adenine dinucleotide / Pyrophosphoric acid |
| Rebamipide Predicted Metabolism Pathway |  | Metabolic | Mesoheme / Rebamipide |
| Refsum Disease |  | Disease | Ascorbic acid / Succinic acid / NADH / ATP / Magnesium cation / Iron / Oxogluric acid / Pyrophosphoric acid |
| Refsum Disease |  | Disease | Ascorbic acid / Succinic acid / NADH / ATP / Magnesium cation / Iron / Oxogluric acid / Pyrophosphoric acid |
| Regadenoson Drug Metabolism |  | Metabolic | Regadenoson |
| Regorafenib Action Pathway |  | Drug Action | Calcium / Regorafenib |
| Regulation of Lipolysis |  | Signaling | Adenosine phosphate / ATP / Norepinephrine / Adenosine / Epinephrine / Dinoprostone / Magnesium cation / Cyclic adenosine monophosphate / Palmitic Acid / Glycerin / Arachidonic Acid / Corticosterone |
| Relaxin IV Signaling Pathway |  | Signaling | Calcium / Magnesium cation / Cyclic adenosine monophosphate |
| Remdesivir Action Pathway |  | Drug Action | Magnesium cation / Pyrophosphoric acid / Remdesivir |
| Remdesivir Predicted Metabolism Pathway |  | Metabolic | Mesoheme / Remdesivir |
| Remifentanil Action Pathway |  | Drug Action | ATP / Norepinephrine / Remifentanil / Dopamine / Potassium cation / Calcium |
| Remifentanil Opioid Analgesic Action Pathway |  | Drug Action | ATP / Remifentanil / Calcium / Magnesium cation / Cyclic adenosine monophosphate / gamma-Aminobutyric acid / Pyrophosphoric acid / Sar9, Met (O2)11-Substance P |
| Remifentanil Opioid Anasthetic Action Pathway |  | Drug Action | ATP / Remifentanil / Calcium / Magnesium cation / Dihydrocodeine / Cyclic adenosine monophosphate / gamma-Aminobutyric acid / Pyrophosphoric acid |
| Remifentanil Predicted Metabolism Pathway |  | Metabolic | Remifentanil / Mesoheme |
| Remimazolam Action Pathway |  | Drug Action | Pyridoxal phosphate / Glutamic acid / ATP / Calcium / Magnesium cation / Cyclic adenosine monophosphate / gamma-Aminobutyric acid / Pyrophosphoric acid |
| Remoxipride Mechanism of Action Action Pathway |  | Drug Action | Pyridoxal phosphate / Tyrosine / Sapropterin / Remoxipride / Dopamine / Levodopa / Calcium / Iron |
| Repaglinide Action Pathway |  | Drug Action | ATP / Repaglinide / Potassium cation / Calcium |
| Repaglinide Action Pathway (New) |  | Drug Action | ATP / Repaglinide / Potassium cation / Calcium |
| Rescinnamine Action Pathway |  | Drug Action | Rescinnamine / Potassium cation / Zinc |
| Reteplase Action Pathway |  | Drug Action | Reteplase / Phylloquinone / Calcium |
| Reteplase Action Pathway (new) |  | Drug Action | Reteplase / Calcium |