How dextromethorphan works
Dextromethorphan suppresses the cough reflex by depressing the cough center in the brainstem. It does this by blocking (antagonizing) the so-called NMDA receptors and by triggering signals (agonism) at sigma-1 receptors.
By interacting with NMDA receptors, dextromethorphan can suppress the perception of pain. For this reason, the active ingredient has also been approved in some countries since 2013 for the treatment of certain painful nerve disorders (neuropathies).
In combination with quinidine sulphate, dextromethorphan is also used to treat pseudobulbar affect disorder. This is an emotional instability that manifests itself in involuntary and sudden episodes of laughter and/or crying.
Background
Coughing is an important reflex to expel foreign bodies from the airways. These include bacteria, viruses or smoke particles that can damage the bronchial mucosa. Such foreign substances are coated with a little mucus and expelled by vigorous coughing (productive mucus).
A dry, irritating cough, on the other hand, has no particular physiological benefit. It is triggered by excessive activity of the cough center in the brain stem following irritation of the mucous membrane.
Absorption, breakdown and excretion
After its distribution in the body, dextromethorphan is broken down in the liver. The resulting metabolic products leave the body mainly via the kidneys (i.e. in the urine).
When is dextromethorphan used?
Dextromethorphan is approved in Germany, Austria and Switzerland for the treatment of dry irritable cough.
In some countries, the active substance is used to treat neuronal pain and, in combination with quinidine sulphate, to treat pseudobulbar affect disorder. In Germany, Austria and Switzerland, these indications fall under the term “off-label use”.
How dextromethorphan is used
The active ingredient can be taken in different dosage forms (such as juice, capsule, lozenge) and different concentrations of the active ingredient. The recommended dosage depends primarily on the particular preparation and the age of the patient.
Non-retarded dosage forms (preparations with immediate release of the active ingredient) are generally taken three to four times a day, while retarded preparations (preparations with delayed release of the active ingredient, e.g. sustained-release tablets) are only taken once or twice a day.
What are the side effects of dextromethorphan?
Hallucinations and impaired consciousness have been observed very rarely in patients (especially in the case of an overdose). If the active substance is abused, dependence may develop.
Overdose
If the dose is too high, dextromethorphan can lead to significant perceptual disturbances, euphoria and unintentional drowsiness and increases the risk of addiction. At the same time, breathing difficulties, a drop in blood pressure, movement disorders (ataxia) and muscle cramps are possible.
If you experience side effects or unmentioned symptoms in connection with the use of the active substance or if you have accidentally taken too much dextromethorphan, please consult your doctor immediately and discontinue the active substance on his advice if necessary.
What should I bear in mind when taking dextromethorphan?
Contraindications
Dextromethorphan must not be taken if:
- hypersensitivity to the active substance or any of the other ingredients of the medicine
- concomitant treatment with antidepressants from the group of monoamine oxidase inhibitors (MAO inhibitors)
- Bronchial asthma
- Chronic obstructive pulmonary disease (COPD)
- Pneumonia (lung inflammation)
- Respiratory dysfunction
Interactions
If you take dextromethorphan at the same time as other medicines, interactions may occur.
- Selective serotonin reuptake inhibitors (SSRIs, such as fluoxetine, sertraline, citalopram)
- Selective serotonin-norepinephrine reuptake inhibitors (SSNRIs, such as venlafaxine and duloxetine)
- Tricyclic antidepressants (such as amitriptyline, imipramine, clomipramine)
Dextromethorphan is metabolized via the enzyme CYP2D6. The 3-methoxymorphinan formed in the process is an inhibitor of CYP2D6. The simultaneous intake of substances that inhibit CYP2D6 or increase its activity can therefore lead to an increased or weakened effect of dextromethorphan. Conversely, dextromethorphan can increase the effect and side effects of drugs that are also broken down via CYP2D6.
This applies in particular to antidepressants (such as SSRI, SSNRI, MAO inhibitors, tricyclic antidepressants), beta-blockers (such as metoprolol, nebivolol), H2-receptor antagonists (such as cimetidine and ranitidine) and some antihistamines (in particular astemizole and terfenadine).
Ask your doctor or pharmacist whether it is safe for you to take dextromethorphan if you are also taking other medicines.
Ability to drive and use machines
Age restriction
The approved minimum age depends on the preparation. If you wish to use dextromethorphan for dry irritable cough in a child, you should ask a doctor or pharmacist which preparation is suitable for this age group.
Pregnancy and breastfeeding
To date, there have been no reports of teratogenic effects, i.e. malformations in children following the use of dextromethorphan during pregnancy. Animal studies also do not indicate any potential risk to humans. According to experts, dextromethorphan can therefore be used as a cough suppressant (antitussive) in all phases of pregnancy. However, use should be limited to a few days.
Although only small amounts of dextromethorphan and its metabolite pass into breast milk, manufacturers advise against its use during breastfeeding for safety reasons.
However, experts consider short-term treatment after the failure of fluid intake and inhalation therapy during breastfeeding to be unproblematic. However, caution is advised for breastfed children with a tendency to respiratory distress, as a respiratory depressant effect cannot be ruled out.
How to obtain medication with dextromethorphan
Dextromethorphan is available in pharmacies in Germany, Austria and Switzerland without a prescription.