Synalgos-DC Side Effects

Generic name: aspirin / caffeine / dihydrocodeine

Medically reviewed by Drugs.com. Last updated on Apr 24, 2025.

Note: This document provides detailed information about Synalgos-DC Side Effects associated with aspirin / caffeine / dihydrocodeine. Some dosage forms listed on this page may not apply specifically to the brand name Synalgos-DC.

Applies to aspirin / caffeine / dihydrocodeine: oral capsule.

Precautions

It is very important that your doctor check your progress while you are using this medicine. This will allow your doctor to see if the medicine is working properly and to decide if you should continue to take it.

This medicine will add to the effects of alcohol and other CNS depressants (medicines that can make you drowsy or less alert). Some examples of CNS depressants are antihistamines or medicine for allergies or colds; sedatives, tranquilizers, or sleeping medicine; other prescription pain medicine or narcotics; medicine for seizures or barbiturates; muscle relaxants; or anesthetics, including some dental anesthetics. Check with your doctor before taking any of these medicines while you are using this medicine.

This medicine may be habit-forming. If you feel that the medicine is not working as well, do not use more than your prescribed dose. Call your doctor for instructions.

This medicine may make you dizzy, drowsy, or lightheaded. Make sure you know how you react to this medicine before you drive, use machines, or do anything else that could be dangerous if you are dizzy or not alert.

Using narcotics for a long time can cause severe constipation. To prevent this, your doctor may direct you to take laxatives, drink a lot of fluids, or increase the amount of fiber in your diet. Be sure to follow the directions carefully, because continuing constipation can lead to more serious problems.

Check with your doctor right away if you have the following symptoms while using this medicine: acid or sour stomach; bloody or black, tarry stools; heartburn; nausea; vomiting; stomach pain; or vomiting of blood or material that looks like coffee grounds.

If you have been using this medicine regularly for several weeks or longer, do not change your dose or suddenly stop using it without checking with your doctor. Your doctor may want you to gradually reduce the amount you are using before stopping it completely. This may help prevent worsening of your condition and reduce the possibility of withdrawal symptoms, such as abdominal or stomach cramps, anxiety, fever, nausea, runny nose, sweating, tremors, or trouble with sleeping.

Do not take other medicines unless they have been discussed with your doctor. This includes prescription or nonprescription (over-the-counter [OTC]) medicines and herbal or vitamin supplements.

Common side effects of Synalgos-DC

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:

Serious side effects of Synalgos-DC

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:

For healthcare professionals

Applies to aspirin / caffeine / dihydrocodeine: oral capsule.

General adverse events

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

Gastrointestinal

Dihydrocodeine:

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

Caffeine:

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

Hypersensitivity

Dihydrocodeine:

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

Respiratory

Dihydrocodeine:

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

Psychiatric

Dihydrocodeine:

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

Caffeine:

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

Dermatologic

Dihydrocodeine:

• Frequency not reported: Sweating, pruritus, skin reactions

Caffeine:

• Frequency not reported: Urticaria^[Ref]

Cardiovascular

Dihydrocodeine:

• Frequency not reported: Orthostatic hypotension

Caffeine:

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

Endocrine

Opioids:

• 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]

Genitourinary

Dihydrocodeine:

• Frequency not reported: Urinary retention^[Ref]

Metabolic

Dihydrocodeine:

• Frequency not reported: Anorexia^[Ref]

Nervous system

Dihydrocodeine:

• Rare (less than 0.1%): Narcosis
• Frequency not reported: Lightheadedness, dizziness, drowsiness, sedation, headache

Caffeine:

• Frequency not reported: Headaches, lightheadedness, tremor

Opioids:

• Frequency not reported: Serotonin syndrome^[Ref]

Ocular

Dihydrocodeine:

• Frequency not reported: Miosis

Caffeine:

• Frequency not reported: Scintillating scotoma^[Ref]

Other

Dihydrocodeine:

• Frequency not reported: Fatigue

Caffeine:

• Frequency not reported: Tinnitus^[Ref]

Renal

Dihydrocodeine:

• Rare (less than 0.1%): Acute renal failure
• Frequency not reported: Granulomatous interstitial nephritis

Caffeine:

• Frequency not reported: Diuresis^[Ref]

See also:

Further information

Synalgos-DC side effects can vary depending on the individual. Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.

Note: Medication side effects may be underreported. If you are experiencing side effects that are not listed, submit a report to the FDA by following this guide.

Medical Disclaimer