From the Guidelines
Sustained-release dextromethorphan (DXM) formulation is effective in suppressing cough, particularly in patients with chronic bronchitis or COPD, with a dose-dependent response, and maximum cough reflex suppression occurring at 60 mg.
Key Points
- The efficacy of DXM in suppressing cough is well-established, with studies showing a significant reduction in cough counts in patients with chronic bronchitis or COPD 1.
- The dose-dependent response of DXM is notable, with higher doses (60 mg) resulting in maximum cough reflex suppression 1.
- DXM has been shown to be effective in reducing cough counts by 40-60% in patients with chronic bronchitis or COPD 1.
- However, the efficacy of DXM in suppressing cough due to upper respiratory tract infections (URIs) is less consistent, with some studies showing a significant reduction in cough frequency and others showing no effect 1.
Mechanism of Action
- DXM is thought to act on the central mechanism of cough, inhibiting the motor control of cough in the brainstem 1.
- The exact mechanism of action of DXM is not fully understood, but it is believed to interact with suprapontine pathways that mediate sensation or the voluntary suppression of cough 1.
Clinical Use
- DXM is commonly used as a cough suppressant in over-the-counter medications, often in combination with other ingredients such as paracetamol 1.
- The recommended dosage of DXM is typically 30-60 mg, with care taken to avoid higher doses due to the potential for adverse effects 1.
- Guidelines for the management of adult lower respiratory tract infections recommend the use of DXM or codeine in patients with a dry and bothersome cough 1.
From the FDA Drug Label
Package/Label Principal Display Panel Compare to Delsym® active ingredient Dextromethorphan Polistirex Extended-Release Oral Suspension Cough Suppressant Active ingredient (in each 5 mL) Dextromethorphan polistirex equivalent to 30 mg dextromethorphan hydrobromide
The effect of sustained-release dextromethorphan (DXM) formulation is to temporarily relieve cough due to minor throat and bronchial irritation, providing 12 Hour Cough Relief.
- The sustained-release formulation allows for extended-duration of action, helping to suppress the impulse to cough and relieve cough symptoms for an extended period. The FDA drug label does support that the formulation is extended-release 2 and contains dextromethorphan polistirex 2, which is equivalent to dextromethorphan hydrobromide.
From the Research
Effects of Sustained-Release Dextromethorphan Formulation
- The effect of sustained-release dextromethorphan (DXM) formulation is not directly addressed in the provided studies 3, 4, 5, 6, 7.
- However, the studies provide information on the pharmacokinetics, pharmacodynamics, and effects of DXM in various contexts.
- DXM is a safe and effective antitussive agent, but at higher doses, it can cause psychoactive effects, making it appealing for abuse 3.
- The pharmacokinetics of DXM can be affected by the route of administration, with substantial first-pass metabolism occurring after intraperitoneal (i.p.) injection compared to subcutaneous (s.c.) administration 5.
- Repeated, high-dose DXM treatment has been shown to decrease neurogenesis and result in depression-like behavior in rats 4.
- DXM and its metabolite 3-hydroxymorphinan have been found to inhibit glutamate release from rat cerebrocortical synaptosomes, which may contribute to their neuroprotective effects 7.
Key Findings
- DXM is metabolized to dextrorphan, which is the major active metabolite, and 3-hydroxymorphinan, the bi-demethylated product 3.
- Genotypic variations in enzymes and interactions with other drugs can result in large inter-individual variability in the pharmacological and toxicological effects produced by DXM 3.
- The abuse of DXM, particularly in combination with other ingredients in over-the-counter (OTC) formulations, is a concern, with potential implications for public health 6.