| Drugs | Constipation mechanism |
| Opioid analgesics | |
| Inhibition of peristalsis which prolong intestinal transit, causing increased absorption of water and electrolytes and lower response of defection. | |
| Antidepressive | Especially tricyclic antidepressants, due to anticholinergic effects. |
| Antimicrobial | Peripheral neuropathies. |
| Antiparkinson | Anticholinergic effects. |
| Antiepileptic | Anticholinergic and dopaminergic effects. |
| Antineoplastic | Peripheral neuropathies. (In few times can change intestinal innervation). |
| Antipsychotic | Anticholinergic effects. |
| Antihypertensive | Reducing smooth muscle contractility. |