Synalgos-DC Side Effects Center

Last updated on RxList: 9/1/2022
Synalgos-DC Side Effects Center

Medical Editor: John P. Cunha, DO, FACOEP

What Is Synalgos-DC?

Synalgos-DC (aspirin, caffeine, and dihydrocodeine bitartrate) is a combination of an analgesic, a narcotic pain reliever, and caffeine, which increases the effects of aspirin, used to treat moderate to moderately severe pain.

What Are Side Effects of Synalgos-DC?

Common side effects of Synalgos-DC include:

  • lightheadedness
  • dizziness
  • drowsiness
  • sedation
  • nausea
  • vomiting
  • constipation
  • itching or rash
  • other skin reactions
  • shaking
  • anxiety
  • agitation
  • sleep problems (insomnia), or
  • ringing in your ears

Tell your doctor if you have serious side effects effects of Synalgos-DC including:

Seek medical care or call 911 at once if you have the following serious side effects:

  • Serious eye symptoms such as sudden vision loss, blurred vision, tunnel vision, eye pain or swelling, or seeing halos around lights;
  • Serious heart symptoms such as fast, irregular, or pounding heartbeats; fluttering in your chest; shortness of breath; and sudden dizziness, lightheartedness, or passing out;
  • Severe headache, confusion, slurred speech, arm or leg weakness, trouble walking, loss of coordination, feeling unsteady, very stiff muscles, high fever, profuse sweating, or tremors.

This document does not contain all possible side effects and others may occur. Check with your physician for additional information about side effects.

Dosage for Synalgos-DC

The usual adult dose of Synalgos-DC is two capsules every 4 hours as needed for pain.

What Drugs, Substances, or Supplements Interact with Synalgos-DC?

Synalgos-DC may interact with other CNS depressants, anticoagulants, and uricosuric agents. Tell your doctor all medications and supplements you use.

Synalgos-DC During Pregnancy or Breastfeeding

Synalgos-DC is not recommended for use during pregnancy. It may harm a fetus and interfere with normal labor/delivery. Dihydrocodeine passes into breast milk and can have adverse effects on nursing infants. Aspirin and caffeine are also excreted in breast milk in small amounts. Consult your doctor before breastfeeding. Withdrawal symptoms may occur if you suddenly stop taking this medication.

Additional Information

Our Synalgos-DC (aspirin, caffeine, and dihydrocodeine bitartrate) Side Effects Drug Center provides a comprehensive view of available drug information on the potential side effects when taking this medication.

This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.


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Get emergency medical help if you have signs of an allergic reaction: hives; difficult breathing; swelling of your face, lips, tongue, or throat.

Opioid medicine can slow or stop your breathing, and death may occur. A person caring for you should seek emergency medical attention if you have slow breathing with long pauses, blue colored lips, or if you are hard to wake up.

Aspirin may cause stomach or intestinal bleeding, which can be fatal. This can occur without warning while you are taking this medicine.

Call your doctor at once if you have:

  • noisy breathing, sighing, shallow breathing, breathing that stops during sleep;
  • a light-headed feeling, like you might pass out;
  • little or no urination;
  • symptoms of stomach bleeding--bloody or tarry stools, coughing up blood or vomit that looks like coffee grounds; or
  • low cortisol levels-- nausea, vomiting, loss of appetite, dizziness, worsening tiredness or weakness.

Seek medical attention right away if you have symptoms of serotonin syndrome, such as: agitation, hallucinations, fever, sweating, shivering, fast heart rate, muscle stiffness, twitching, loss of coordination, nausea, vomiting, or diarrhea.

Serious side effects may be more likely in older adults and those who are overweight, malnourished, or debilitated.

Long-term use of opioid medication may affect fertility (ability to have children) in men or women. It is not known whether opioid effects on fertility are permanent.

Common side effects may include:

  • dizziness, drowsiness;
  • nausea, vomiting, constipation; or
  • itching, mild rash.

This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.


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The following serious adverse reactions are described, or described in greater detail, in other sections:

The following adverse reactions associated with the use of SYNALGOS-DC 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.

Many adverse reactions due to aspirin ingestion are dose-related. The following is a list of adverse reactions that have been reported in the literature [see WARNINGS AND PRECAUTIONS].

Body as a Whole: Fever, hypothermia, thirst.

Cardiovascular: Dysrhythmias, hypotension, tachycardia.

Central Nervous System: Agitation, cerebral edema, coma, confusion, dizziness, headache, subdural or intracranial hemorrhage, lethargy, seizures.

Fluid and Electrolyte: Dehydration, hyperkalemia, metabolic acidosis, respiratory alkalosis.

Gastrointestinal: Dyspepsia, GI bleeding, ulceration and perforation, nausea, vomiting, transient elevations of hepatic enzymes, hepatitis, Reye's syndrome, pancreatitis.

Hematologic: Prolongation of the prothrombin time, disseminated intravascular coagulation, coagulopathy, thrombocytopenia.

Hypersensitivity: Acute anaphylaxis, angioedema, asthma, bronchospasm, laryngeal edema, urticaria.

Musculoskeletal: Rhabdomyolysis.

Metabolism: Hypoglycemia (in children), hyperglycemia.

Reproductive: Prolonged pregnancy and labor, stillbirths, lower birth weight infants, antepartum and postpartum bleeding.

Respiratory: Hyperpnea, pulmonary edema, tachypnea.

Special Senses: Hearing loss, tinnitus. Patients with high frequency hearing loss may have difficulty perceiving tinnitus. In these patients, tinnitus cannot be used as a clinical indicator of salicylism.

Urogenital: Interstitial nephritis, papillary necrosis, proteinuria, renal insufficiency and failure.

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 SYNALGOS-DC.

Androgen Deficiency: Cases of androgen deficiency have occurred with chronic use of opioids [see CLINICAL PHARMACOLOGY].

Read the entire FDA prescribing information for Synalgos-DC (Aspirin, Caffeine, and Dihydrocodeine Bitartrate Capsules, USP)

© Synalgos-DC Patient Information is supplied by Cerner Multum, Inc. and Synalgos-DC Consumer information is supplied by First Databank, Inc., used under license and subject to their respective copyrights.

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