Morphine also releases histamine from mast cells leading to local effects such as urticaria and pruritis at the site of injection or systemic effects such as bronchospasm and hypotension.
The immune system is depressed by long term opioid use.
Morphine is slowly and erratically absorbed.
nausea and vomiting (particularly in initial stages)
difficulty with micturition
ureteric or biliary spasm
decreased libido or potency
larger doses produce respiratory depression, hypotension, and muscle rigidity
Opioids (narcotic analgesics) cause coma, respiratory depression, and pinpoint pupils in overdose. The specific antidote naloxone is indicated if there is coma or bradypnoea.
acute respiratory depression
risk of paralytic ileus
raised intracranial pressure or head injury (affects pupillary responses vital for neurological assessment)
avoid injection in phaeochromocytoma (risk of pressor response to histamine release)
pregnancy & breast-feeding
asthma (avoid during attack) and decreased respiratory reserve
may precipitate coma in hepatic impairment (reduce dose or avoid but many such patients tolerate well)
reduce dose or avoid in renal impairment, elderly and debilitated,
dependence (severe withdrawal symptoms if withdrawn abruptly)
use of cough suppressants containing opioid analgesics not generally recommended in children and should be avoided altogether in those under at least 1 year