Morphine is an extremely powerful opiate analgesic drug and is the principal active agent in opium. Like other opiates, morphine acts directly on the central nervous system (CNS) to relieve pain, and at synapses of the arcuate nucleus, in particular. Side effects include impairment of mental performance, euphoria, drowsiness, lethargy, and blurred vision. It also decreases hunger, inhibits the cough reflex, and produces constipation. Morphine is highly addictive when compared to other substances, and tolerance and physical and psychological dependence develop quickly. Patients on morphine often report insomnia and nightmares.
Morphine may be given parenterally as subcutaneous, intravenous, or epidural injections. When injected, particularly intravenously, morphine produces an intense contraction sensation in the muscles and thus produces a powerful 'rush'. The military sometimes issues morphine loaded in an autoinjector.
Orally, it comes as an elixir, concentrated solution, powder (for compounding) or in tablet form. Morphine is rarely supplied in suppository form. Due to its poor oral bioavailability, oral morphine is only one-sixth to one-third of the potency of parenteral morphine. Morphine is available in extended-release capsules for chronic administration, as well as immediate-release formulations.
Morphine is used legally:
- analgesic in hospital settings for
- Pain after surgery
- Pain associated with trauma
- In the relief of severe chronic pain
- Cancer pain
- Pain from kidney stones
- As an adjunct to general anesthesia
- In epidural anesthesia
- For palliative care (i.e. to alleviate pain without curing the underlying reason for it)
- As an antitussive for severe cough
- As an antidiarrheal in chronic conditions (e.g., for diarrhea associated with AIDS)
- To relieve breathlessness in patients in respiratory failure
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