What the label lists and what reports show
Dextromethorphan and quinidine side effects
Dextromethorphan and quinidine's FDA label: “The most common adverse reactions (incidence of ≥ 3% and two-fold greater than placebo) in patients taking dextromethorphan hydrobromide and quinidine sulfate are diarrhea, dizziness, cough, vomiting, asthenia, peripheral edema, urinary tract infection …” FAERS holds 3,617 reports naming it through July 30, 2026; the reaction reported most often, leaving out the conditions it is used for, product-use terms and outcomes, is fall (207 reports).
- Generic approved
Check it at the source: the dextromethorphan and quinidine FDA label on DailyMed (effective July 8, 2026, Sun Pharmaceutical Industries, Inc.); the FDA FAERS public dashboard.
What does the label list?
From the label: adverse reactionsThe most common adverse reactions (incidence of ≥ 3% and two-fold greater than placebo) in patients taking dextromethorphan hydrobromide and quinidine sulfate are diarrhea, dizziness, cough, vomiting, asthenia, peripheral edema, urinary tract infection, influenza, increased gamma-glutamyltransferase, and flatulence.
A table the label prints in its adverse reactions section without a title; its column headings name the groups compared
| Reaction | Dextromethorphan hydrobromide and quinidine sulfate N = 107 % | Placebo N = 109 % |
|---|---|---|
| Diarrhea | 13 | 6 |
| Dizziness | 10 | 5 |
| Cough | 5 | 2 |
| Vomiting | 5 | 1 |
| Asthenia | 5 | 2 |
| Peripheral edema | 5 | 1 |
| Urinary tract infection | 4 | 1 |
| Influenza | 4 | 1 |
| Increased gamma-glutamyltransferase | 3 | 0 |
| Flatulence | 3 | 1 |
Rows and numbers as the label prints them, under its own column headings (the first rows of a longer table where it runs on). A reaction in a trial table is not necessarily caused by the medicine, and trials differ from everyday use.
From the label: adverse reactions, continuedA total of 946 patients participated in four Phase 3 controlled and uncontrolled PBA studies and received at least one dose of the combination product of dextromethorphan/quinidine in various strengths at the recommended or higher than the recommended dose. Of those patients, 393 patients were exposed for at least 180 days and 294 patients were exposed for at least one year. Median exposure was 168 days. Controlled trials enrolled only patients with either ALS or MS. Uncontrolled studies enrolled 136 patients with PBA secondary to a wide variety of underlying neurological conditions including stroke (45 patients) and traumatic brain injury (23 patients). Consequently, patients with other underlying neurologic diseases may experience other adverse reactions not described below. The most common adverse reactions (incidence of ≥ 3% and two-fold greater than placebo) in patients taking dextromethorphan hydrobromide and quinidine sulfate are diarrhea, dizziness, cough, vomiting, asthenia, peripheral edema, urinary tract infection, influenza, increased gamma-glutamyltransferase, and flatulence. ( 6.1 ) To report suspected adverse reactions, contact Sun Pharmaceutical Industries, Inc. at 1-800-818-4555 or FDA at 1-800-FDA-1088 or www.fda.gov/medwatch. …
Source: FDA drug label, Sun Pharmaceutical Industries, Inc., effective July 8, 2026 (SPL set 92b54ac4-594e-47b8-a4d3-394a29b425f3), via openFDA; the full label on DailyMed
What do FAERS reports show?
3,617 reports list dextromethorphan and quinidine among the medicines taken, each a report of something that happened, not proof the medicine caused it; 278 are coded as a death and 500 as a hospital stay. Counts follow how widely a medicine is used and watched, and they are not a measure of how risky it is. Of the 16 reactions below, 6 are named by the same term (in US spelling) in the label's adverse reactions, warnings or patient leaflet; a reaction the label does not name may still be there under another word, and a report does not show that the medicine caused it.
Reports received each year
The 25 most reported reactions
Source: FDA Adverse Event Reporting System (FAERS) via openFDA, reports through July 30, 2026; reactions as MedDRA preferred terms
What next?
- Dextromethorphan and quinidine: the full record
- label, generics, price, shortages, recalls
- Report a side effect to the FDA
- MedWatch
- Side effects hub
- the most reported medicines and reactions