Mersyndol (Paracetamol, Codeine Phosphate Hemihydrate, Doxylamine Succinate)
Complete patient guide for uses, dosage, side effects, and safety information
Prescription RequiredQuick Facts
What Is Mersyndol Used For?
Mersyndol is a combination pain reliever designed for short-term use to manage moderate pain and reduce fever when other treatment options aren’t effective or suitable.
Primary Uses
Short-term relief of moderate pain and fever
How It Works
Contains three active ingredients that work together: Paracetamol reduces pain and fever, Codeine (converted to morphine in the body) provides stronger pain relief, and Doxylamine has calming effects. Together, they block pain messages from reaching the brain.
Limited Use: Should only be used when your doctor decides other treatment options cannot effectively manage your pain or you cannot tolerate them
How to Take Mersyndol
Take Mersyndol exactly as prescribed by your doctor. It can be taken with or without food and should be swallowed whole with a glass of water.
Dosage Instructions
Adults and children 12 years or over: Take 1-2 tablets every 4-6 hours as needed for pain relief. Do not take more than 8 tablets in a 24-hour period. Not recommended for children under 12 years.
What If You Miss a Dose?
If you miss a dose, do not try to make up for it. If it’s almost time for your next dose, skip the missed dose and take your next dose when scheduled. Always wait 4-6 hours between doses.
Important: Never take a double dose to make up for a missed dose. Do not exceed 8 tablets in 24 hours.
Available Tablet Strengths
Side Effects
Like all medications, this medicine can cause side effects. Most are mild and temporary, but some require medical attention.
Common Side Effects
These side effects occur relatively frequently and usually don’t require emergency care:
- Skin rash
- Constipation
- Nausea
- Vomiting
- Dizziness
- Drowsiness
- Sweating
- Blurred vision
- Dry mouth
- Headache
- Fatigue
- Sleep problems
Seek immediate medical attention if you experience:
- Difficulty breathing or shallow breathing
- Swelling of face, lips, mouth, throat
- Hives or severe skin reactions
- Irregular heartbeat
- Confusion or extreme mood changes
- Severe bleeding or bruising
- Signs of liver problems (yellowing skin/eyes, dark urine)
- Severe abdominal pain
- Mouth ulcers with fever
- Fainting or unconsciousness
Important Warnings
Mersyndol contains codeine which can be habit-forming and poses risks of abuse, misuse, and addiction. It can also cause life-threatening breathing problems.
Who Should Not Take Mersyndol
Do not use if you have: allergies to any ingredients, severe respiratory disease, breathing problems, severe liver failure, G6PD deficiency, are a CYP 2D6 ultra-rapid metabolizer, are aged 12-18 with respiratory issues, are pregnant/breastfeeding, have drug/alcohol dependence history, are taking MAOIs, or are under 12 years old.
Medical Conditions to Discuss
Tell your doctor if you have: liver/kidney problems, heart issues, breathing conditions, sleep apnea, prostate/thyroid problems, seizures, head injury, chronic constipation, glaucoma, urinary problems, or history of substance abuse.
Pregnancy and Breastfeeding
Do not take during third trimester of pregnancy, during labor (especially with premature babies), or while breastfeeding. Can cause breathing problems and withdrawal symptoms in newborns.
Life-threatening Risk: Can cause fatal breathing problems even at recommended doses. Risk is higher when starting treatment, after dose increases, in elderly patients, or those with lung problems.
Drug Interactions
Many medications can interact with Mersyndol, potentially causing dangerous drowsiness, breathing problems, or affecting how well it works.
Alcohol Warning: Never drink alcohol while taking Mersyndol – can cause severe drowsiness, breathing problems, coma, and death
- Sleeping tablets and benzodiazepines
- Other pain relievers and opioids
- Antihistamines
- Antidepressants (especially MAOIs)
- Antipsychotics
- Gabapentinoids (epilepsy/nerve pain medicines)
- Blood thinning medicines
- Medicines containing alcohol
- Metoclopramide or domperidone
- Antibiotics like chloramphenicol
- CYP 2D6 inhibitors (fluoxetine, paroxetine)
- CYP 3A4 inducers (rifampicin)
Alcohol & Driving
Mersyndol can significantly impair your ability to drive safely and must never be combined with alcohol.
Alcohol
Absolutely do not drink alcohol while taking Mersyndol. Combining them increases drowsiness risk and can cause liver damage, severe breathing problems, coma, and death.
Driving and Operating Machinery
Do not drive, operate machinery, or do anything dangerous while taking Mersyndol. It can cause drowsiness, dizziness, and light-headedness, especially after the first dose. Children should not ride bicycles and need supervision.
Storage
Store Mersyndol below 30°C in a cool, dry place away from moisture, heat, and sunlight. Keep tablets in their original pack until use. Store in a locked cupboard at least 1.5 meters high, away from children. Do not store in bathrooms, cars, or on windowsills.
Overdose Information
Overdose symptoms include slow/difficult breathing, drowsiness, unconsciousness, slow heartbeat, nausea, vomiting, seizures, and mental impairment. Large amounts of paracetamol can cause liver damage. If overdose occurs, immediately call 000 for an ambulance, contact the Poisons Information Centre (13 11 26), or go to the nearest emergency department. Keep the person awake and bring this medication information with you.
Frequently Asked Questions
The medication information doesn’t specify exact onset time, but it’s designed for pain relief when taken every 4-6 hours as needed.
Yes, Mersyndol can be taken with or without food. Swallow the tablets whole with a glass of water.
Yes, Mersyndol contains codeine which can be habit-forming and poses risks of abuse, misuse, and addiction. You can become addicted even when taking it exactly as prescribed.
Stopping suddenly can cause withdrawal symptoms including nervousness, body aches, loss of appetite, increased heart rate, watery eyes, runny nose, chills, and increased sweating. Continue taking as directed by your doctor.
Absolutely not. Never drink alcohol while taking Mersyndol as it can cause severe drowsiness, breathing problems, coma, and death. It can also cause liver damage when combined with paracetamol.
Elderly patients should talk to their doctor about dosing as they may have less effective kidney function due to age, increasing the risk of side effects. They’re also at higher risk for breathing problems.
Don’t try to make up for missed doses. If it’s almost time for your next dose, skip the missed dose and take the next one when scheduled. Always wait 4-6 hours between doses and never double dose.
Important Disclaimer
This information is intended for general educational purposes only and should not be considered medical advice. Always consult your healthcare provider or pharmacist before starting, stopping, or changing any medication.
If you think you may have a medical emergency, call your doctor or emergency services immediately.