Table 1.

Effects of opioids on different organ systems.

System	Effects
Gastrointestinal	Constipation, xerostomia, nausea, vomiting, delayed gastric emptying, gastro-oesophageal reflux, constriction of the sphincter of Oddi
Neurological	Analgesia, delirium, hallucinations, sedation, myoclonus, hyperalgesia, seizures, headaches, euphoria, dysphoria, tolerance, dependency
Cardiovascular	Bradycardia, hypotension
Pulmonary	Respiratory depression, decreased cough reflex, non-cardiogenic pulmonary oedema
Urological	Urine retention, decreased urine production, altered renal function
Endocrinological	Hypogonadism, sexual dysfunction, osteoporosis
Immunological	Decreased neutrophil, macrophage, natural killer cell, T cell function and cytokine dysregulation

Adapted with permission from Boland, J.W. Clin. Med. 2013, 13, 149–151 [9].