Side effects constipation, ileus, altered taste and mood, abnormal thinking, headache, dizziness, sedation, sweating, rash, flushing, chills, involuntary muscle contraction, bronchospasms, decreased cough, dry mouth, asthenia, malaise, circulatory and respiratory depression, cardiac and respiratory arrest, shock, apnoea, hypo, hypertension, syncope, oedema, palpitation, tachy, bradycardia, SVT, tremor, hypertonia, ureteric, biliary spasm/pain, elevated LFT’s, paraesthesia, confusion, insomnia, agitation, anxiety, delirium, dys/euphoria, hallucination, seizures, visual disturbance’s, miosis, nystagmus, anaphylaxis, hyperglycaemia, prolactin release, adrenal insufficiency, SIADH, amenorrhea, infertility, sexual/erectile dysfunction, reduced libido, hypogonadism, decreased cortisol & testosterone, urinary retention, dependence, tolerance, withdrawal, serotonin syndrome, hyperalgesia