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Finding out How Morphine Interacts with other Drugs

Posted in Acute Pain, Chronic Pain, morphine

If you are using any other medications apart from Morphine let your doctor know, so that your doctor can judge how other medications are going to interact with Morphine. Let us find out how morphine interacts with other drugs

Drug interactions may change how your medications work or increase your risk for serious side effects. This document does not contain all possible drug interactions. Keep a list of all the products you use (including prescription/nonprescription drugs and herbal products) and share it with your doctor and pharmacist. Do not start, stop, or change the dosage of any medicines without your doctor’s approval.

Some products that may interact with this drug are: certain pain medications (mixed opioid agonist/antagonists such as pentazocine, nalbuphine, butorphanol), naltrexone.

The risk of serious side effects (such as slow/shallow breathing, severe drowsiness/dizziness) may be increased if this medication is used with other products that may also cause drowsiness or breathing problems. Tell your doctor or pharmacist if you are taking other products such as other opioid pain or cough relievers (such as codeine, hydrocodone), alcoholmarijuana (cannabis), drugs for sleep or anxiety (such as alprazolam, lorazepam, zolpidem), muscle relaxants (such as carisoprodolcyclobenzaprine), or antihistamines (such as cetirizine, diphenhydramine).

Check the labels on all your medicines (such as allergy or cough-and-cold products) because they may contain ingredients that cause drowsiness. Ask your pharmacist about using those products safely.

Morphine can interact with

  • Muscle relaxants
  • CNS depressants
  • MAOIs
  • PGP(P-Glycoprotein inhibitors)
  • Anticholinergics

Let your doctor know if you are using any other non prescription, prescription medications, OTC medications, dietary or nutritional supplements, recreational herbal remedies, and or illegal drugs.

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Morphine Drug Interactions

CNS depressants

The parallel use of morphine with CNS depressants comprising of tranquilizers, hypnotics, sedatives, phenothiazines, general anesthetics or other opioids and alcohol can enhance the harmful effects like respiratory depression, coma, profound sedation and even death. Patients receiving morphine and CNS depressants should be monitored for signs of hypotension, sedation and respiratory depression.

Muscle Relaxants

Morphine can increase the neuromuscular blocking activity of various muscle relaxants (skeletal) and generate high level of respiratory depression. Patients receiving muscle relaxants and morphine together should be monitored for the signs of high level of respiratory depression.


MAOIs can affect the efficiency of morphine. Patients who are given combination of an MAOI and morphine should be monitored for high level of central nervous system and respiratory depression.  MAOIs affect the morphine anxiety, respiratory depression, coma or confusion. Morphine should not be prescribed to the patients using MAOIs or stopped using the treatment at least for 14 days.


Morphine can decrease the potency of diuretics by instigating the liberation of antidiuretic hormone. Morphine can also cause urinary retention and thus resulting in sphincter spasm of bladder especially in men having enlarged prostates.


Cimetidine can affect morphine-generated respiratory depression. According to a report a patient undergoing the process of hemodialysis, when administered parallel with cimetidine and morphine reported signs of serious respiratory depression and confusion.


Anticholinergics when used simultaneously with opioid analgesics can increase the risk of severe constipation or urinary retention. Patients should be monitored for signs of decreased gastric motility and urinary retention when using morphine and Anticholinergics concurrently.

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Mixed Antagonist/Agonist and Partial Agonist- Opioid Analgesics

Mixed Antagonist/Agonist and Partial Agonist (Opioid Analgesics) can lower the efficiency of morphine or increase withdrawal symptoms. Do not use antagonist/agonist or partial analgesics with morphine.

PGP Inhibitors

PGP inhibitors can enhance the absorption of morphine to a large extent. Therefore patients using the two medications together should be monitored for central nervous system or respiratory depression.

Before you start taking morphine consult your health care provider to know about various morphine drug interactions with the medications you are using currently. The medications you are using might interact with morphine to produce harmful effects that you might not be aware of. Make a list of all other medications you are using and share the list with your doctor to avoid complications and use drug safely.

Your doctor can check for ingredients present in medication you are using and can advice you on whether morphine is safe to be used with those medications. Avoid changing your dose or stop taking morphine suddenly.

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