How does this medication work? What will it do for me?

This combination product contains three medications: acetylsalicylic acid (ASA), methocarbamol, and codeine.

ASA belongs to the group of medications called analgesics (pain relievers), anti-inflammatories, and antipyretics (fever reducers).

Methocarbamol belongs to the group of medications called muscle relaxants.

Codeine belongs to the group of medications called narcotic analgesics.

ASA - methocarbamol - codeine phosphate is used for the relief of moderate pain associated with muscle spasm, strains and sprains, low back pain, tendon pain, and muscle pain resulting from injury.

This medication may be available under multiple brand names and/or in several different forms. Any specific brand name of this medication may not be available in all of the forms or approved for all of the conditions discussed here. As well, some forms of this medication may not be used for all of the conditions discussed here.

Your doctor may have suggested this medication for conditions other than those listed in these drug information articles. If you have not discussed this with your doctor or are not sure why you are taking this medication, speak to your doctor. Do not stop taking this medication without consulting your doctor.

Do not give this medication to anyone else, even if they have the same symptoms as you do. It can be harmful for people to take this medication if their doctor has not prescribed it.

What form(s) does this medication come in?

Methoxisal-C is no longer being manufactured for sale in Canada. For brands that may still be available, search under ASA - methocarbamol - codeine. This article is being kept available for reference purposes only. If you are using this medication, speak with your doctor or pharmacist for information about your treatment options.

How should I use this medication?

The usual adult dose is 1 or 2 tablets 3 or 4 times daily. No more than 8 tablets should be taken within a 24-hour period.  This medication should be used at the lowest effective dose for the shortest duration of time.

This medication should be swallowed whole with a glass of water. Do not crush or chew the tablets. It may be taken with food or on an empty stomach.

Many things can affect the dose of medication that a person needs, such as body weight, other medical conditions, and other medications. If your doctor has recommended a dose different from the ones listed here, do not change the way that you are taking the medication without consulting your doctor.

If you have been taking this medication for more than a few days, do not abruptly stop taking it. The body gets used to the changes this medication causes (tolerance) and stopping the medication suddenly can lead to withdrawal effects, such as tremor, nausea, and diarrhea. Talk to your doctor about a plan to gradually decrease the amount of medication you are taking, to minimize the withdrawal symptoms.

It is important to take this medication exactly as prescribed by your doctor. If your doctor has told you to take this medication on a regular basis and you miss a dose, take it as soon as possible and continue with your regular schedule. If it is almost time for your next dose, skip the missed dose and continue with your regular dosing schedule. Do not take a double dose to make up for a missed one. If you are not sure what to do after missing a dose, contact your doctor or pharmacist for advice.

Store this medication at room temperature, protect it from light and moisture, and keep it out of the reach of children.

Do not dispose of medications in wastewater (e.g. down the sink or in the toilet) or in household garbage. Ask your pharmacist how to dispose of medications that are no longer needed or have expired.

Who should NOT take this medication?

Do not use this medication if you:

  • are allergic to methocarbamol, ASA, codeine, or any ingredients of the medication
  • are allergic to codeine-like narcotics (e.g., morphine)
  • are pregnant or breast-feeding
  • are at risk of blocked intestines
  • have a head injury or increased pressure inside the brain
  • have seizures
  • have an active stomach ulcer
  • have had a bronchospastic reaction (severe asthma-type reaction), generalized hives, severe running and itching nose, or shock brought on by ASA or nonsteroidal anti-inflammatory drugs
  • are intoxicated with alcohol or other medications that can depress breathing and consciousness, such as hypnotics, other opioids (e.g., codeine or morphine), or psychotropic medications (certain medications for mental health conditions)
  • are experiencing acute alcoholism or delirium tremens
  • are experiencing acute asthma or other obstructive airway disease
  • are experiencing acute respiratory depression
  • are experiencing sudden, severe abdominal pain that may require surgery (e.g., appendicitis, pancreatitis)
  • are less than 18 years old and have had a tonsillectomy or surgery to treat sleep apnea syndrome
  • are less than 18 years old and have chickenpox or the flu
  • have mild pain that can be treated with other pain medications
  • have severe liver damage or other conditions that create clotting problems
  • have taken monoamine oxidase (MAO) inhibitor medications (e.g., phenelzine, tranylcypromine) within the last 14 days
  • have been told by your doctor that you are an "ultra-rapid metabolizer" of codeine

What side effects are possible with this medication?

Many medications can cause side effects. A side effect is an unwanted response to a medication when it is taken in normal doses. Side effects can be mild or severe, temporary or permanent.

The side effects listed below are not experienced by everyone who takes this medication. If you are concerned about side effects, discuss the risks and benefits of this medication with your doctor.

The following side effects have been reported by at least 1% of people taking this medication. Many of these side effects can be managed, and some may go away on their own over time.

Contact your doctor if you experience these side effects and they are severe or bothersome. Your pharmacist may be able to advise you on managing side effects.

  • decreased sexual ability
  • dizziness
  • drowsiness
  • dry mouth
  • headache
  • nausea
  • sweating
  • trouble sleeping
  • vomiting
  • weakness

Although most of these side effects listed below don't happen very often, they could lead to serious problems if you do not seek medical attention.

Check with your doctor as soon as possible if any of the following side effects occur:

  • constipation
  • decreased coordination
  • fainting
  • fast, slow, or irregular heartbeat
  • poor appetite
  • symptoms of Reye's syndrome (e.g., rash on the palms of hands and feet, severe vomiting, high fever, weakness, confusion, headache, fast breathing, unresponsiveness, death)
  • symptoms of serotonin syndrome (e.g., agitation, restlessness, loss of muscle control, muscle twitching)
  • vision changes

Stop taking the medication and seek immediate medical attention if any of the following occur:

  • signs of a serious allergic reaction (e.g., abdominal cramps, difficulty breathing, nausea and vomiting, or swelling of the face and throat)
  • signs of breathing problems such as shallow, irregular breathing, or slow or troubled breathing
  • symptoms of overdose of codeine, such as:
    • abnormally slow, weak breathing
    • cold, clammy skin
    • confusion
    • extreme drowsiness
    • severe dizziness
    • slow heartbeat
  • symptoms of withdrawal, such as:
    • anxiety
    • body aches
    • cold and clammy skin
    • diarrhea
    • loss of appetite
    • nausea
    • shivering
    • sweating
    • vomiting

Some people may experience side effects other than those listed. Check with your doctor if you notice any symptom that worries you while you are taking this medication.

Are there any other precautions or warnings for this medication?

Before you begin using a medication, be sure to inform your doctor of any medical conditions or allergies you may have, any medications you are taking, whether you are pregnant or breast-feeding, and any other significant facts about your health. These factors may affect how you should use this medication.


June 8, 2021

Health Canada has issued new information concerning the use of non-steroidal anti-inflammatory drugs (NSAIDs). To read the full Health Canada Advisory, visit Health Canada's web site at

A previous advisory on ASA - methocarbamol - codeine was issued on July 31, 2020.

Abdominal conditions: Codeine, like other narcotic medications, may make the diagnosis of abdominal conditions more difficult or it may worsen these conditions. If you are scheduled for abdominal surgery or have an abdominal condition such as inflammatory or obstructive bowel disease, acute cholecystitis, or pancreatitis, discuss with your doctor how this medication may affect your medical condition, how your medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed.

Accidental Use: When methocarbamol - ASA - codeine is used by anyone other than the person for whom it was prescribed, the effects of the medication may be fatal. Children are especially at risk. Keep this medication out of sight and reach of children.

Alcohol and other medications that cause drowsiness: Do not consume alcohol while taking this medication, as this may lead to dangerous and even fatal side effects. Other medications that cause drowsiness or slow down your breathing (e.g., antidepressants, sleeping pills, anxiety medications) should be avoided if possible, as additive side effect may occur and can be dangerous and possibly fatal.

Breathing: Codeine can suppress breathing. Children are more likely to experience serious breathing problems, including death. For this reason, this medication should not be given to people less than 18 years old. If you are at risk for breathing difficulties, such as asthma, discuss with your doctor how this medication may affect your medical condition, how your medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed.

Constipation: Codeine can be very constipating. Eating a high-fibre diet and following good bowel habits will help to minimize this effect. If you develop constipation easily, discuss with your doctor how this medication may affect your medical condition, how your medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed.

Dependence and withdrawal: This medication contains codeine. Physical dependence, psychological dependence, and abuse have occurred with the use of codeine. People with a history of past or current substance use problems may be at greater risk of developing abuse or addiction while taking this medication. Abuse is not a problem with people who require this medication for pain relief.

If you suddenly stop taking this medication, you may experience withdrawal symptoms such as anxiety, sweating, trouble sleeping, shaking, pain, nausea, tremors, diarrhea, and hallucinations. If you have been taking this medication for a while, it should be stopped gradually as directed by your doctor.

Drowsiness/reduced alertness: This medication may cause drowsiness. Do not drive, operate machinery, or perform other potentially hazardous tasks until you have determined how this medication affects you.

Head injury: If you have a head injury or increased pressure in the head, you may have a higher risk of experiencing side effects (breathing problems) or worsening of their condition while taking this medication. Discuss with your doctor how this medication may affect your medical condition, how your medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed.

Kidney function: Taking ASA - methocarbamol - codeine over a long period of time may increase the risk of developing kidney disease. If you have kidney disease or reduced kidney function, discuss with your doctor how this medication may affect your medical condition, how your medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed.

Liver function: If you have liver disease or reduced liver function, discuss with your doctor how this medication may affect your medical condition, how your medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed.

Other medical conditions: This medication can have an effect on other medical conditions. The codeine may make symptoms of delirium tremens or acute alcohol intoxication worse. As well, this medication may cause symptoms of low thyroid (hypothyroidism), Addison's disease, benign prostatic hypertrophy (enlarged prostate), bleeding disorders, gallbladder disease, stomach ulcers, urethral stricture, decreased function of the adrenal glands, or porphyria to become worse. If you have any of these conditions, discuss with your doctor how this medication may affect your medical condition, how your medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed.

Serotonin syndrome: Although rare, severe reactions are possible when codeine is combined with other medications that act on serotonin, such as tricyclic antidepressants and serotonin reuptake inhibitors, medications used to treat depression. These combinations should be avoided if possible. Symptoms of a reaction may include muscle rigidity and spasms, difficulty moving, changes in mental state including delirium and agitation. Coma and death are possible. 

If you are taking antidepressants, discuss with your doctor how this medication may affect your medical condition, how your medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed.

Sleep apnea: Sleep apnea is a condition where you stop breathing for short periods while asleep. This can be caused or made worse by medications that slow breathing such as codeine. If you or your partner notices episodes where you are not breathing then suddenly start to breathe again, contact your doctor as soon as possible.

Surgery: Do not take ASA - methocarbamol - codeine for 5 to 7 days before any surgery, including dental surgery, unless otherwise directed by your doctor or dentist. If you are scheduled for surgery, let your doctor know that you are taking this medication.

Pregnancy: This medication should not be used during pregnancy unless the benefits outweigh the risks. Infants born to birthing parents who have taken codeine during pregnancy have been born with signs of narcotic withdrawal. Additionally, babies born to birthing parents who have taken anti-inflammatory medications regularly throughout pregnancy have a higher risk of being born with kidney problems or high blood pressure, as well as other complications during pregnancy. If you become pregnant while taking this medication, contact your doctor immediately.

Breast-feeding: Codeine passes into breast milk. Some of the codeine dose is converted into morphine by the body, once it has been taken. For some people, this change happens much faster than for others. If this happens to someone who is breast-feeding, the baby is at risk of receiving a morphine overdose through the breast milk. ASA – methocarbamol – codeine is not recommended for those who are breast-feeding.

Children: Children are more likely to experience harmful effects associated with codeine use. Do not give ASA - methocarbamol - codeine to children less than 18 years old.

The use of ASA may be associated with the development of Reye's syndrome in children and teenagers who have illnesses accompanied by fever, especially influenza and chickenpox. ASA should not be given to, or used by, children or teenagers who have chickenpox or flu symptoms unless a doctor is consulted.

Seniors: Seniors may be more susceptible to the harmful effects of ASA.

What other drugs could interact with this medication?

There may be an interaction between ASA - methocarbamol - codeine and any of the following:

  • abiraterone acetate
  • acetazolamide
  • aclidinium
  • alcohol
  • alendronate
  • amphetamines (e.g., dextroamphetamine, lisdexamfetamine)
  • anagrelide
  • angiotensin-converting enzyme inhibitors (ACEIs; e.g., captopril, ramipril)
  • antihistamines (e.g., azelastine, cetirizine, dimenhydrinate, diphenhydramine, hydroxyzine, rupatadine)
  • antipsychotics (e.g., cariprazine, chlorpromazine, clozapine, haloperidol, quetiapine, olanzapine, risperidone)
  • apalutamide
  • apixaban
  • atropine
  • 'azole' antifungals (e.g., fluconazole, itraconazole, ketoconazole, voriconazole)
  • barbiturates (e.g., butalbital, phenobarbital)
  • benzodiazepines (e.g., alprazolam, clonazepam, diazepam, lorazepam)
  • benztropine
  • bismuth subsalicylate
  • bosentan
  • botulinum toxin
  • brimonidine
  • bromocriptine
  • buprenorphine
  • bupropion
  • butorphanol
  • certain calcium channel blockers (e.g., diltiazem, verapamil)
  • cannabis
  • ceritinib
  • chloral hydrate
  • cinacalcet
  • clidinium
  • clonidine
  • clopidogrel
  • corticosteroids (e.g., dexamethasone, prednisone, methylprednisolone)
  • crizotinib
  • dabigatran
  • darifenacin
  • desmopressin
  • diabetes medications (e.g., acarbose, gliclazide, glyburide, insulin, metformin, sitagliptin)
  • diphenoxylate
  • dipyridamole
  • disopyramide
  • diuretics (water pills; e.g., furosemide, hydrochlorothiazide, triamterene)
  • domperidone
  • dronedarone
  • edoxaban
  • entacapone
  • enzalutamide
  • eplerenone
  • esketamine
  • fesoterodine
  • flibanserin
  • flunarizine
  • fluoroquinolone antibiotics (e.g., ciprofloxacin, norfloxacin, moxifloxacin)
  • general anesthetics (medications used to put people to sleep before surgery)
  • glycopyrrolate
  • gold injections
  • grapefruit juice
  • heparin
  • herbal products that affect blood clotting (e.g., garlic, ginger, ginkgo, ginseng)
  • HIV non-nucleoside reverse transcriptase inhibitors (e.g., efavirenz, etravirine)
  • HIV protease inhibitors (e.g., atazanavir, darunavir, lopinavir, ritonavir)
  • hyaluronidase
  • hydroxychloroquine
  • icosapent ethyl
  • ipratropium
  • kava kava
  • ketotifen
  • lemborexant
  • letermovir
  • linezolid
  • lithium
  • low-molecular-weight heparins (e.g., dalteparin, enoxaparin, tinzaparin)
  • lumacaftor and ivacaftor
  • macrolide antibiotics (e.g., clarithromycin, erythromycin)
  • methadone
  • methazolamide
  • methotrexate
  • metoclopramide
  • mifepristone
  • mirabegron
  • mirtazapine
  • modafinil
  • monoamine oxidase inhibitors (e.g., tranylcypromine, phenelzine, moclobemide, rasagiline, selegiline)
  • multivitamin supplements
  • nabilone
  • naltrexone
  • nirmatrelvir
  • obinutuzumab
  • other medications that contain acetylsalicylic acid (ASA)
  • other muscle relaxants (e.g., baclofen, cyclobenzaprine, orphenadrine)
  • other narcotic pain relievers (e.g., codeine, fentanyl, morphine, oxycodone, tapentadol, tramadol)
  • other non-steroidal anti-inflammatory medications (NSAIDs; e.g., celecoxib, diclofenac, ibuprofen, ketorolac, naproxen)
  • omega-3 fatty acids
  • oxybutynin
  • peginterferon alfa-2b
  • pegvisomant
  • pentoxifylline
  • perampanel
  • pizotifen
  • pomalidomide
  • pramipexole
  • prasugrel
  • pregabalin
  • propiverine
  • protein kinase inhibitors (e.g., ceritinib, imatinib, sunitinib)
  • prucalopride
  • quinine
  • rifabutin
  • rifampin
  • rivaroxaban
  • ropinirole
  • rotigotine
  • scopolamine
  • selective serotonin reuptake inhibitors (e.g., citalopram, fluoxetine, sertraline, vortioxetine)
  • serotonin/norepinephrine reuptake inhibitors (SNRIs; e.g., desvenlafaxine, duloxetine, venlafaxine)
  • seizure medications (e.g., clobazam,  gabapentin, levetiracetam, phenobarbital, phenytoin, primidone, rufinamide, topiramate, valproic acid)
  • sodium oxybate
  • solifenacin
  • somatostatin analogues (e.g., lanreotide, octreotide, pasireotide)
  • St. John's wort
  • spironolactone
  • sulfamethoxazole
  • terbinafine
  • tetrabenazine
  • tetracycline antibiotics (e.g., doxycycline, minocycline, tetracycline)
  • thalidomide
  • ticagrelor
  • tiotropium
  • tizanidine
  • tolterodine
  • trazodone
  • tricyclic antidepressants (e.g., amitriptyline, clomipramine, desipramine, imipramine)
  • trihexyphenidyl
  • trospium
  • tryptophan
  • umeclidinium
  • vaccines
  • valerian
  • vitamin E
  • warfarin
  • zolpidem
  • zopiclone

If you are taking any of these medications, speak with your doctor or pharmacist. Depending on your specific circumstances, your doctor may want you to:

  • stop taking one of the medications,
  • change one of the medications to another,
  • change how you are taking one or both of the medications, or
  • leave everything as is.

An interaction between two medications does not always mean that you must stop taking one of them. Speak to your doctor about how any drug interactions are being managed or should be managed.

Medications other than those listed above may interact with this medication. Tell your doctor or prescriber about all prescription, over-the-counter (non-prescription), and herbal medications you are taking. Also tell them about any supplements you take. Since caffeine, alcohol, the nicotine from cigarettes, or street drugs can affect the action of many medications, you should let your prescriber know if you use them.


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