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Aspirin / caffeine / dihydrocodeine Side Effects

For the Consumer

Applies to aspirin/caffeine/dihydrocodeine: oral capsule

Along with its needed effects, aspirin/caffeine/dihydrocodeine may cause some unwanted effects. Although not all of these side effects may occur, if they do occur they may need medical attention.

Check with your doctor immediately if any of the following side effects occur while taking aspirin / caffeine / dihydrocodeine:

Incidence Not Known

  • Agitation
  • anxiety
  • bleeding gums
  • bloating
  • bloody or black, tarry stools
  • bloody or cloudy urine
  • blue lips and fingernails
  • blurred vision
  • chest pain or discomfort
  • chills
  • cold sweats
  • confusion
  • constipation
  • continuing ringing or buzzing or other unexplained noise in the ears
  • cool, pale skin
  • coughing that sometimes produces a pink frothy sputum
  • dark urine
  • darkening of the skin
  • depression
  • diarrhea
  • difficult, fast, noisy breathing
  • dizziness, faintness, or lightheadedness when getting up suddenly from a lying or sitting position
  • drowsiness
  • dry mouth
  • fast, pounding, or irregular heartbeat or pulse
  • fast, slow, or irregular heartbeat
  • fever
  • flushed, dry skin
  • fruit-like breath odor
  • general tiredness and weakness
  • greatly decreased frequency of urination or amount of urine
  • headache
  • headache, sudden and severe
  • hearing loss
  • heartburn
  • increased hunger
  • increased sweating
  • increased thirst
  • increased urination
  • indigestion
  • large, hive-like swelling on the face, eyelids, lips, tongue, throat, hands, legs, feet, or genitals
  • light-colored stools
  • loss of appetite
  • loss of consciousness
  • muscle cramps, spasms, pain, weakness, or stiffness
  • muscle tremors
  • nausea
  • nervousness
  • nightmares
  • numbness and tingling of the face, lips, hands, and feet
  • overactive reflexes
  • pains in the stomach, side, or abdomen, possibly radiating to the back
  • pinpoint red spots on the skin
  • poor coordination
  • rapid, deep breathing
  • restlessness
  • seizures
  • severe stomach pain
  • shakiness
  • shivering
  • skin rash
  • slurred speech
  • stomach pain, cramping, or burning
  • sunken eyes
  • swelling in the legs, feet, or ankles
  • trembling or shaking
  • trouble with breathing
  • twitching
  • unexplained weight loss
  • unusual bleeding or bruising
  • unusual drowsiness, dullness, tiredness, weakness, or feeling of sluggishness
  • upper right abdominal pain
  • vomiting
  • vomiting of blood or material that looks like coffee grounds
  • vomiting, severe or continuous
  • weakness or heaviness of the legs
  • wrinkled skin
  • yellow eyes or skin

Get emergency help immediately if any of the following symptoms of overdose occur while taking aspirin / caffeine / dihydrocodeine:

Symptoms of Overdose

  • Extreme sleepiness
  • irregular, fast or slow, or shallow breathing

Some side effects of aspirin / caffeine / dihydrocodeine may occur that usually do not need medical attention. These side effects may go away during treatment as your body adjusts to the medicine. Also, your health care professional may be able to tell you about ways to prevent or reduce some of these side effects. Check with your health care professional if any of the following side effects continue or are bothersome or if you have any questions about them:

Incidence Not Known

  • Belching
  • clumsiness
  • low body temperature
  • sleepiness
  • weak or feeble pulse
  • weight gain

For Healthcare Professionals

Applies to aspirin / caffeine / dihydrocodeine: oral capsule


The most frequently expected adverse reactions based on the individual components include lightheadedness, dizziness, drowsiness, sedation, nausea, vomiting, constipation, pruritus and skin reactions.[Ref]



Frequency not reported: Nausea, vomiting, constipation, abdominal pain, diarrhea, dry mouth, indigestion, spasm of biliary tract


Frequency not reported: Diarrhea, nausea, stomach pain, vomiting[Ref]



Frequency not reported: Anaphylactoid reactions, hypersensitivity reactions[Ref]



Frequency not reported: Respiratory depression, cough suppression[Ref]



Frequency not reported: Confusion, physical and psychological dependence, hallucinations vivid dreams


Frequency not reported: Anxiety, anxiety neurosis, excitement, insomnia, irritability, restlessness, tenseness[Ref]



Frequency not reported: Sweating, pruritus, skin reactions


Frequency not reported: Urticaria[Ref]



Frequency not reported: Orthostatic hypotension


Frequency not reported: Extrasystoles, palpitations, tachycardia[Ref]



Frequency not reported: Adrenal insufficiency, androgen deficiency[Ref]

Chronic opioid use may influence the hypothalamic-pituitary-gonadal axis and lead to androgen deficiency; however, the causal role of opioids is unknown due to the lack of studies into the many medical, physical, lifestyle, and psychological stressors that influence gonadal hormone levels.[Ref]



Frequency not reported: Urinary retention[Ref]



Frequency not reported: Anorexia[Ref]

Nervous system


Rare (less than 0.1%): Narcosis

Frequency not reported: Lightheadedness, dizziness, drowsiness, sedation, headache


Frequency not reported: Headaches, lightheadedness, tremor


Frequency not reported: Serotonin syndrome[Ref]



Frequency not reported: Miosis


Frequency not reported: Scintillating scotoma[Ref]



Frequency not reported: Fatigue


Frequency not reported: Tinnitus[Ref]



Rare (less than 0.1%): Acute renal failure

Frequency not reported: Granulomatous interstitial nephritis


Frequency not reported: Diuresis[Ref]


1. "Product Information. Synalgos-DC (aspirin / caffeine / dihydrocodeine (ASA/caffeine/dihydrocodeine))." Sun Pharmaceutical Industries, Cranbury, NJ.

2. "Product Information. Trezix (acetaminophen/caffeine/dihydrocodeine)." WraSer Pharmaceuticals, Madison, MS.

3. US Food and Drug Administration "Opioid Pain Medicines: Drug Safety Communication - New Safety Warnings Added to Prescription Opioid Medications. Available from: URL:" ([2016, Mar 22]):

Further information

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.

Some side effects may not be reported. You may report them to the FDA.