As a nurse, be careful not to confuse morphine with hydromorphone or morphine sulfate with magnesium sulfate.
What Are the Uses of Morphine?
The Food and Drug Administration has approved the use of morphine sulfate for moderate to severe pain, ranging from acute to chronic. In clinical practice, morphine is most commonly used for pain management, providing relief to patients afflicted with severe pain. Clinical situations in which morphine seems to benefit greatly are the management of palliative or end-of-life care patients, active cancer treatment pain, and vaso-occlusive episode pain during sickle cell crisis.
In addition to other conditions, morphine is commonly used off-label for almost any condition that causes debilitating pain. In the emergency department, it relieves musculoskeletal pain, arthritis, abdominal pain, chest pain, and even headaches that do not respond well to first- or second-line treatment. For minor procedures where mild sedation is required, healthcare providers may combine a low dose of morphine with a low dose of a benzodiazepine like lorazepam.
Moreover, patients with active acute coronary syndrome also receive morphine in the emergency setting before proceeding to the cath lab; morphine also helps relieve pain due to myocardial infarction. It is a potent opioid with effective pain-relieving properties that lead to a decrease in the activation of the autonomic nervous system, which is desirable during an acute heart attack. Morphine can decrease heart rate, blood pressure, and venous return and stimulate histamine-mediated processes, in turn reducing myocardial oxygen demand.
Onset, Peak, and Duration of Action
The onset of action, peak, and duration of action of morphine in various dosage forms can be summarized as follows:
- The onset of action of morphine oral solution and tablets occurs in 30 minutes, the peak occurs in 1 hour, and the duration of action is 3 to 5 hours.
- When given in an extended-release tablet dosage form, the peak occurs in 3 to 4 hours, and the duration of action remains for 8 to 12 hours.
- Intravenous (IV) morphine acts rapidly; the peak occurs within half an hour, and the duration of action is 3 to 5 hours.
- When given through the intramuscular (IM) route, the onset of action occurs in 10 to 30 minutes, the peak occurs in 0.5 to 1 hour, and the duration of action is 3 to 5 hours.
- Through the epidural route, the onset of action of morphine occurs in 15 to 60 minutes, peak in 1 hour, and duration of action for 12 to 20 hours. When given subcutaneously, the onset of action occurs in 10 to 30 minutes, achieves peak in 1 to 5 hours, and duration of action for 3 to 5 hours.
- When administered rectally, the onset of action occurs in 20 to 60 minutes, peak occurs in 0.5 to 1 hour, with duration of action for 3 to 7 hours.
Morphine is variably absorbed from the gastrointestinal tract and readily absorbed after IM and subcutaneous administration, having protein binding of 20 to 35%, and is widely distributed throughout the body. Moreover, it is metabolized in the liver and primarily excreted in urine. Morphine is removed by hemodialysis and has a half-life of 2 to 4 hours, which can be increased in hepatic diseases.
Morphine crosses the placenta and is distributed in breast milk. It may prolong labor if administered in the latent phase of the first stage of labor or before 4 to 5 cm dilation has occurred. In neonates, it can cause respiratory depression if the mother receives morphine during labor. Regular use of opiates during pregnancy by the mother can cause withdrawal symptoms in the neonate, causing excessive crying, irritability, hyperactive reflexes, tremors, fever, diarrhea, vomiting, seizures, sneezing, and yawning.
Morphine, when given to children, can lead to paradoxical excitement in those younger than two years and are more susceptible to respiratory depression. When given to the elderly, paradoxical excitement may occur. It may also cause age-related renal impairment and may also increase the risk of urinary retention.
Contraindications and Precautions for Morphine
Morphine use is contraindicated in patients hypersensitive to it, those with acute or severe asthma, gastrointestinal obstruction, concurrent use of monoamine oxidase inhibitors within 14 days, known or suspected cases of paralytic ileus, and severe respiratory depression.
Exercise extreme caution with morphine use in patients with chronic obstructive pulmonary disease (COPD), hypoxia, hypercapnia, pre-existing respiratory depression, head injury, increased intracranial pressure, severe hypotension, pancreatitis, Addisons disease, biliary tract disease, morbid obesity, elderly, cardiovascular disease, adrenal insufficiency, urethral stricture, hypothyroidism, prostatic hyperplasia, patients with central nervous system (CNS) depression, debilitated patients, toxic psychosis, alcoholism, and seizure disorder.
Morphine has the following black box warnings:
- Risk of severe side effects when given through the epidural route
- Extended-release morphine intake with alcohol can increase the risk of overdose
- Risk of opioid addiction, misuse, and abuse
- Serious life-threatening respiratory depression
- Long-term use in pregnancy can cause neonatal opioid withdrawal syndrome
- Concomitant use of benzodiazepines or other CNS depressants. Their combined effects can lead to profound CNS depression, respiratory depression, coma, or even death.
How Morphine Acts?
Morphine binds to the opiate receptors in the CNS. It alters the pain perception and response to the stimuli while producing generalized CNS depression, eventually causing a decrease in pain severity. Like other opioid analgesics, morphine has an affinity for delta, kappa, and mu-opioid receptors. It produces analgesic effects by binding to the mu-opioid receptors in the central and peripheral nervous system. Moreover, it activates the descending inhibitory pathways of the CNS and causes the inhibition of nociceptive afferent neurons of the peripheral nervous system (PNS), leading to an overall reduction of nociceptive transmission.
Naltrexone is added with morphine in an Embeda preparation to prevent drug abuse or misuse by altering the formulation. Naltrexone has no effect if the capsule is chewed or crushed.
Drug Interactions
Morphine, when given with alcohol or other CNS depressant drugs, such as gabapentin, zolpidem, lorazepam, and others, can lead to increased CNS effects, leading to respiratory depression and hypotension. With monoamine oxidase inhibitors (MAOIs), such as selegiline and phenelzine, morphine administration can lead to serotonin syndrome- a life-threatening condition. If you have to administer any of these drugs together, the dosage of morphine may need to be reduced to one-fourth of the usual dose.
Herbal drugs with sedative effects, such as kava, valerian, and chamomile, can lead to increased sedative effects with morphine and also cause increased CNS depression.
Morphine may increase serum amylase and lipase. Therefore, those levels need to be monitored with ongoing morphine therapy.
Administration and Handling
Morphine can be given undiluted. To reconstitute an IV injection, it may be diluted in sterile water for injection of 0.9% sodium chloride (NaCl) to a final concentration of 1 to 2 mg/ml. For continuous IV infusion, dilute the solution to a concentration of 0.1 to 1 mg/ml in dextrose water and give it through a controlled infusion device.
Always administer morphine slowly. Rapid IV administration of morphine can increase the risk of severe adverse reactions such as apnea, chest wall rigidity, peripheral circulatory collapse, cardiac arrest, and anaphylactoid reaction.
Store the vials at room temperature. For IM and subcutaneous administration, rotate injection sites and administer very slowly. Patients with circulatory impairment experience an increased risk of overdosage because of delayed absorption of repeated administration.
For oral administration, morphine can be given without regard to food. You can mix the liquid form of morphine with fruit juices for improved taste and better patient compliance. Do not crush, break, dissolve, or divide the extended-release capsules or tablets. With Avinza or Kadian administration, you may mix applesauce before administration.
Moreover, for administration of morphine through the rectal route, moisten the suppository well with cold water before inserting the well into the rectum. If it is too soft, chill the suppository for 30 minutes in the refrigerator or run cold water over it before administration.
Side Effects
Morphine can cause various side effects such as dizziness, confusion, sedation, euphoria, dysphoria, a floating feeling, headache, unusual dreams, hallucinations, diplopia, blurred vision, miosis, bradycardia, hypotension, adrenal insufficiency, constipation, nausea, vomiting, urinary retention, itching, flushing, and sweating.
The most problematic adverse effect of morphine therapy is physical and psychological dependence and tolerance, which causes difficulty in drug withdrawal.
Nursing Considerations
Assess the type, location, and intensity of pain one hour after oral, IM, and subcutaneous administration and 20 minutes after IV administration. When titrating the morphine dose, increase it by 25 to 50% until there is a 50% reduction in the patients pain rating on a numerical or visual analog scale, or the patient reports satisfactory pain relief. For short-acting morphine, a repeat dose can be administered with ease at the time of peak if the previous dose was ineffective and the side effects are minimal.
Patients receiving a continuous infusion should get an additional bolus every 15 to 30 minutes as needed for breakthrough pain. The bolus dose is often set concerning the amount of drug infused each hour by continuous infusion. Moreover, those receiving extended-release morphine may require additional short-acting doses for breakthrough pain. The dosage of short-acting opioids should be equivalent to 10 to 20% of 24 hours total and given every two hours as required. When changing the route of administration of one opioid drug to another, consider using an equianalgesic chart that helps you calculate the exact dose.
Be high alert to assess the patients level of consciousness, blood pressure, pulse, and respiration before and periodically with morphine administration. If the respiratory rate is ten breaths per minute, assess the level of sedation. Physical stimulation may be sufficient to prevent significant hypoventilation. Decrease subsequent doses by 25 to 50% if the patient remains deeply sedated with a low respiratory rate. Initial drowsiness will continue to diminish with continued morphine use. Keep a keen eye on the senior population with morphine administration because the elderly population is more sensitive to the effects of opioids and is at risk of developing respiratory depression and other opioid-related complications. Children are also sensitive to the effects of opioid analgesics and may experience respiratory complications, excitability, and restlessness more frequently.
Long-term use of opioids can lead to physical and psychological dependence on the drug. However, that should not prevent them from getting adequate analgesia. Many patients who receive morphine for analgesic effects do not develop psychological dependencies, and progressively increased doses of morphine are required to achieve adequate pain control in long-term therapy.
Monitor the patient's bowel function daily. Take measures to prevent constipation with increased fluid intake and administer laxatives to the patient. Also, administer stimulant laxatives routinely if opioid use is for more than 2 to 3 days.
Assess the patient for risk of opioid addiction, abuse, or misuse before its administration. Drug abuse or misuse by crushing, chewing, snorting extended-release preparations, or injecting dissolved products will lead to uncontrolled delivery of morphine, which can result in morphine overdose and death. Naloxone is the antidote to treat opioid overdose or to treat respiratory depression or coma.
The Bottom Line
Morphine is a Schedule II opioid agonist that, when given for a long time, can cause physical and psychological dependence. However, it remains an essential agent for analgesia, often for postoperative patients or those with cancer-associated pain. Compel your patients to attend follow-up visits when receiving morphine therapy, report any adverse effects to you promptly, and do not combine any over-the-counter CNS depressant with it unless the prescriber allows.
About the Author:
Mariya Rizwan is an experienced pharmacist who has been working as a medical writer for four years. Her passion lies in crafting articles on topics ranging from Pharmacology, General Medicine, Pathology to Pharmacognosy.
Mariya is an independent contributor to CEUfast's Nursing Blog Program. Please note that the views, thoughts, and opinions expressed in this blog post are solely of the independent contributor and do not necessarily represent those of CEUfast. This blog post is not medical advice. Always consult with your personal healthcare provider for any health-related questions or concerns.
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