The following serious adverse reactions are described, or described in greater detail, in other sections:
The following adverse reactions associated with the use of morphine were identified in clinical studies or postmarketing reports. Because some of these reactions were reported voluntarily from a population of uncertain size, it is not always possible to reliably estimate their frequency or establish a causal relationship to drug exposure.
Serious adverse reactions associated with Morphine Sulfate Injection included respiratory depression, apnea, and to a lesser degree, circulatory depression, respiratory arrest, shock, and cardiac arrest. Rarely, anaphylactoid reactions have been reported when morphine or other phenanthrene alkaloids of opium are administered intravenously.
The most frequently observed adverse reactions included sedation, lightheadedness, dizziness, nausea, vomiting, constipation, and diaphoresis.
Lightheadedness, dizziness, sedation, nausea, vomiting and sweating seem to be more prominent in ambulatory patients and in those who are not suffering from severe pain. In such individuals, lower doses are advisable.
Other possible adverse reactions included:
CNS – Euphoria, dysphoria, weakness, headache, agitation, tremor, uncoordinated muscle movements, visual disturbances, transient hallucinations, disorientation, delirium, somnolence, drowsiness, miosis, pinpoint pupils, coma, insomnia, impairment of mental and physical performance, mental clouding, lethargy, anxiety, fear, psychic dependence, mood changes, confusion.
Gastrointestinal – Constipation, biliary tract spasm, dry mouth, anorexia. Patients with chronic ulcerative colitis may experience increased colonic motility; toxic dilatation has been reported in patients with acute ulcerative colitis.
Cardiovascular – Tachycardia, bradycardia, palpitation, faintness, syncope, orthostatic hypotension, peripheral circulatory collapse, hypotension, phlebitis following intravenous injection.
Genitourinary – Oliguria and urinary retention or hesitancy; an antidiuretic effect has been reported; ureteral spasm and spasm of vesical sphincters, reduced libido and/or potency.
Allergic – Pruritus, urticaria, skin rashes, edema, and (rarely) hemorrhagic urticaria. Flare over the vein with intravenous injection may occur. Anaphylactoid reactions have been reported following intravenous administration. An isolated case of thrombocytopenia has been reported to be induced by morphine.
Other – Opioid-induced histamine release may be responsible for the flushing of the face, diaphoresis, and pruritus often seen with these drugs. Wheals and urticaria at the site of injection are probably related to histamine release. Local tissue irritation, pain, and induration have been reported following repeated subcutaneous injection. Morphine may alter temperature regulation in susceptible individuals and will depress the cough reflex.
Serotonin syndrome: Cases of serotonin syndrome, a potentially life-threatening condition, have been reported during concomitant use of opioids with serotonergic drugs.
Adrenal insufficiency: Cases of adrenal insufficiency have been reported with opioid use, more often following greater than one month of use.
Anaphylaxis: Anaphylaxis has been reported with ingredients contained in Morphine Sulfate Injection.
Androgen deficiency: Cases of androgen deficiency have occurred with chronic use of opioids (see CLINICAL PHARMACOLOGY).
Chat online with Pfizer Medical Information regarding your inquiry on a Pfizer medicine.
*Contact Medical Information. 8AM-9PM ET Monday to Friday; excluding holidays.
Submit a medical question for Pfizer prescription products.
To report an adverse event related to the Pfizer-BioNTech COVID-19 Vaccine, and you are
not part of a clinical trial* for this product, click the link below to submit your
*If you are involved in a clinical trial for this product, adverse
events should be reported to your coordinating study site.
If you cannot use the above website, or would like to report an adverse event related
to a different Pfizer product, please call Pfizer Safety at
You may also contact the U.S. Food and Drug Administration (FDA) directly to report
adverse events or product quality concerns either online at