Dextromethorphan (oral)

Dextromethorphan is a non-prescription drug that is used to provide relieve for the coughs that are often caused by influenza or colds.


Dextromethorphan is an over the counter medication that is used to relieve the irritation of coughs that occur as a side effect of influenza and colds. This drug is not suitable for use with coughs that generate a lot of phlegm or mucus, and those that are typically caused by asthma, smoking, or emphysema.

Dextromethorphan works to prevent coughing by acting directly on the part of the brain that triggers the cough response.

This medication is suitable for use in adults and children over four years of age. It should be noted that over the counter cold and cough preparations are not suitable for babies or children under the age of four years. Serious and potentially fatal side effects can result from giving these types of medicines to very young children.

Dextromethorphan comes in a variety of forms for oral use, including:

  • Solution
  • Extended release suspension
  • Syrup
  • Lozenge
  • Capsule
  • Troche
  • Elixir
  • Liquid filled capsule
  • Tablet
  • Suspension
  • Liquid

This drug is sold in the US under a variety of different brand names, although the drug the products contain is essentially the same. Brands available include:

  • Vicks 44 Cough Relief
  • St Joseph
  • Simply Cough
  • Silphen DM
  • Robitussin
  • Robafen Cough
  • Pediacare Long-Acting Cough
  • Pediacare
  • Nycoff
  • Miltuss
  • Father Johns Medicine
  • ElixSure Cough Childrens
  • Dexalone
  • Delsym
  • Creo-Terpin
  • Creomulsion
  • Childrens Pedia Care
  • Benylin Pediatric Formula
  • Babee Cof Syrup

Conditions treated

  • Coughs

Type of medicine

  • Oral

Side effects

In addition to the effects that are intended, some medication can cause unwanted side effects in some people. You may not experience any of the effects mentioned in the list below, but if you do, you should consult your GP as you may require further medical assistance.

If you notice any of the following effects, you should check with your GP as these could be symptomatic of an overdose:

  • Unusual nervousness, excitement, irritability, or restlessness
  • Slowed breathing
  • Shakiness and unsteady walk
  • Severe nausea or vomiting
  • Drowsiness or dizziness
  • Difficulty in urination
  • Confusion
  • Blurred vision

Some people report other effects that do not generally need medical attention. The effects often disappear after a few days, once your body gets used to the new medicine. Your doctor may be able to give you some advice on how you can manage or prevent any side effects that you may be experiencing. If any of the effects persist or prove to be especially annoying, ask your GP for advice.

  • Stomach pain
  • Nausea or vomiting
  • Headache
  • Drowsiness (mild)
  • Dizziness (mild)
  • Constipation
  • Confusion

There may be some side effects that have been noted by other patients that are not listed here. If you notice any other odd effects that are troubling, stop using the medicine and consult your GP.


Before you begin using dextromethorphan, mention to your doctor if you are on a special diet, especially one that is very low in sodium or low in sugar. Many drugs do not just contain the active ingredient that is shown on the main label, and many syrups and solutions also contain a small amount of alcohol.

You should always take this medication exactly as instructed by your GP or follow the instructions given on the label. You must not use more of it, use it for longer than directed, or take it more often than is recommended. In rare cases, dextromethorphan can be habit-forming, meaning that using it for long periods could cause physical or mental dependence to develop.

The dose of dextromethorphan usually varies somewhat between different people. If you have not been told how much to take by your doctor, follow the instructions on the product label. Note that the information contained in this guide refers only to the average dose. If the dose you have been told to take is different from this, don't alter the amount unless you are told to by your GP.

The quantity of dextromethorphan that you are advised to use will depend on the potency of the preparation. The nature and severity of your illness and your age will dictate how many daily doses you need to take, the time you leave between doses, and for how long you continue to use the drug.

The variants of the drug form have different dosage instructions, as follows:


Allow lozenges to dissolve in your mouth before swallowing them to reduce the danger of choking.

  • Adults: 5 mg to 15 mg, one time 2 to 4 hours daily as required.
  • Children aged over 12: 5 mg to 15 mg, one time 2 to 4 hours daily as required.
  • Children aged six to 12: 5 mg to 15 mg, one time 2 to 6 hours daily as required.
  • Children aged four to six: 5 mg every 4 hours daily as required.
  • Use not recommended in children under four years of age.


  • Adults and children aged over 12: 30 mg, one time 6 to 8 hours daily as required.
  • Children aged six to 12 years of age: 7 mg, one time 6 to 8 hours daily as required.
  • Children aged four to six years: 3.5 mg one time every 4 hours or 7.5 mg every six 6 daily as required.
  • Use not recommended in children under four years of age.

Extended-release oral suspension

  • Adults and children aged over 12: 60 mg, one time 12 hours daily as required.
  • Children aged six to 12: 30 mg, one time daily every 12 hours as required.
  • Children aged four to six: 15 mg one time every 12 hours daily as required.
  • Use not recommended in children under four years of age.

If you forget to take a dose of dextromethorphan, try to take it promptly. If it is nearly time for your next scheduled dose, miss this one out and just pick up where you left off. Do not take two lots of medicine to make up for the dose that you missed.

If the cough has not shown signs of improvement after seven days of using the medicine, you should seek medical advice. Similarly, if you have a sore throat that has not become better after two days, or if you have a high fever, a persistent headache, and a skin rash in addition to your cough, you should check with your GP. In addition, if you suffer from asthma or hypertension, you should consult your doctor. All these symptoms could be indicative of an underlying medical condition that is responsible for your cough.


There are some drugs that should never be used together, as to do so could cause a serious interaction. In other instances, it may be safe to use two or more different medications at the same time, even though this may result in an interaction. If this is applicable to you, your GP might change the dose of your medicines or recommend other action you can take to manage or prevent the interaction. Before you start taking dextromethorphan, you must tell your doctor if you are taking any of the drugs that are shown in the bulleted list below. Using dextromethorphan with any of these medicines is not recommended:

  • Tranylcypromine
  • Toloxatone
  • Selegiline
  • Rasagiline
  • Procarbazine
  • Phenelzine
  • Pargyline
  • Nialamide
  • Moclobemide
  • Isocarboxazid
  • Iproniazid
  • Clorgyline

It is not generally recommended to use dextromethorphan with any of the following drugs, although it may be necessary to do so in some cases. If you are prescribed any of these medicines together, your GP may change the dose or the frequency of their use:

  • Ziprasidone
  • Vortioxetine
  • Vilazodone
  • Venlafaxine
  • Trimipramine
  • Trazodone
  • Tramadol
  • Sibutramine
  • Sertraline
  • Protriptyline
  • Paroxetine
  • Panobinostat
  • Palonosetron
  • Oxycodone
  • Nortriptyline
  • Mirtazapine
  • Milnacipran
  • Methylene Blue
  • Meperidine
  • Memantine
  • Lorcaserin
  • Linezolid
  • Levomilnacipran
  • Imipramine
  • Hydroxytryptophan
  • Granisetron
  • Fluvoxamine
  • Fluoxetine
  • Fentanyl
  • Escitalopram
  • Duloxetine
  • Doxepin
  • Dolasetron
  • Desvenlafaxine
  • Desipramine
  • Darunavir
  • Clomipramine
  • Citalopram
  • Bupropion
  • Buprenorphine
  • Amoxapine
  • Amitriptyline
  • Almotriptan

Taking dextromethorphan with any of the medications in the bulleted list that follows can increase the likelihood that you will suffer certain side effects. However, if using both drugs is the best treatment option in your case, your doctor may recommend doing so, but with different dosage rates in usage frequency.

  • Quinidine
  • Haloperidol
  • Clobazam
  • Abiraterone

There are some medicines that can interact adversely with some food groups, foods, tobacco, or alcohol. To be on the safe side, ask your GP if it is safe to use dextromethorphan with foods, alcohol, and tobacco.


When you decide to use any form of drug, you should weigh up the risks against the benefits of doing so. This decision should be made following discussions with your GP.

Mention to your GP any strange reactions that you have had to this medication or to any other drugs, and allergies that you are aware of to certain food groups, food colorant, preservatives, or animal derivatives. When using over the counter medicines, check the label carefully to make sure that the product does not contain anything that you are allergic to.

You should not use dextromethorphan in children aged under four years, as the drug could cause very serious and potentially fatal side effects. Ask your GP's advice if your child has a persistent cough.

As far as studies can determine, it is safe to take dextromethorphan whilst breastfeeding. However, you might want to discuss this with your midwife before you begin using the medicine.

Medical history

Some health conditions can affect the safe use of dextromethorphan. Always tell your GP if you suffer from or have a history of any health problems, particularly the following.

If you suffer from asthma, you should not use this medicine. As dextromethorphan prevents coughing, you may experience difficulty in shifting any mucus that has collected in your airways or lungs.

Some medications, especially cough syrup, contain sugar. This could cause problems if you suffer from diabetes and may adversely affect how you control your blood sugar levels.

Patients with liver disease or decreased liver function may experience unexpected side effects, due to a build-up of the medicine in their body.

You should not use dextromethorphan if you suffer from a chronic illness that causes phlegm or mucus to collect in your airways or lungs. This medicine damps down the cough brain's cough reflex, meaning that you may be unable to shift the mucus, potentially leading to complications such as a chest infection or pneumonia. Do not use this drug if you have chronic bronchitis or emphysema.

Dextromethorphan can slow down a person's breathing rate. Do not use this medicine if you already have a condition that causes your breathing to slow down.


All the forms of dextromethorphan should be stored in their original containers, away from direct heat, sunlight, and moisture. Do not refrigerate or freeze the medicines.

Be sure to store the medicines out of reach of children and pets. Cough syrups tend to be very sweet and are often flavored to make them more palatable, making them very attractive to small children. However, they also contain alcohol and could be dangerous if consumed in large quantities.

Do not use medicines that are out of date or damaged.

Do not throw unwanted drugs out with your trash without wrapping them securely in a sealed bag so that they cannot be accessed by animals or children. Do not flush medicines down the toilet or drains.


Dextromethorphan is a non-prescription drug used to relieve coughs that are symptomatic of influenza and colds. This medicine should not be used to treat coughs that generate a lot of phlegm or mucus, such as those that are typically caused by asthma, smoking, or emphysema. Dextromethorphan works by acting directly on the part of the brain that triggers the cough response. If you have a cough that is accompanied by large amounts of mucus, not coughing to remove it could cause a build-up of phlegm in your lungs, potentially leading to pneumonia or a serious chest infection.

There is a long list of medications that should not be used with dextromethorphan. There are also a number of medical conditions that may be made worse by using this drug. Always consult your doctor for advice if you are unsure whether this is the right medicine for use with your condition. Dextromethorphan should not be given to children under the age of four.