Taking two montelukast tablets instead of one is unlikely to cause any serious harm. The standard adult dose is 10 mg, so a double dose would be 20 mg, which is far below the levels that have been tested safely in clinical settings. Adults have taken up to 200 mg per day (20 times the recommended dose) for five months in clinical trials with no dose-related adverse effects observed.
Why a Double Dose Is Not Dangerous
Montelukast has a wide safety margin, meaning there’s a large gap between the normal dose and a dose that would cause real problems. In a study of over 17,000 accidental montelukast exposures in children aged 5 to 17, no serious or life-threatening events were reported, even at doses up to 445 mg (more than 40 times the adult dose). Fewer than 2% of those children experienced any symptoms at all. For an adult who accidentally took 20 mg, the risk is extremely low.
The medication reaches its peak level in your bloodstream about 3 to 4 hours after you take it, and it clears relatively quickly, with a half-life of roughly 2.7 to 5.5 hours in healthy adults. That means your body will process the extra dose and return to normal levels within several hours.
Symptoms You Might Notice
Most people who take an extra dose feel nothing at all. If you do experience anything, the most commonly reported symptoms from higher-than-normal doses are mild: stomach pain, nausea, vomiting, drowsiness, or feeling restless and agitated. These tend to resolve on their own as the drug works through your system.
In the large study of pediatric exposures, abdominal pain was the single most common complaint, occurring in only about 1.5% of cases even among children who took 50 mg or more. Vomiting was the next most frequent, at roughly 1%. The vast majority of cases (96%) were managed at home without any visit to a healthcare facility.
What You Should Do Now
Skip your next dose. Since you’ve already taken two, you don’t want to add a third within 24 hours. Resume your normal one-tablet schedule the following day. There’s no need to take any special steps to “flush” the extra medication from your system.
If you feel fine, which is the most likely outcome, there’s nothing else you need to do. If you develop stomach discomfort or drowsiness, it should pass within a few hours as the drug is eliminated.
When to Call for Help
For a single extra tablet, emergency care is almost never needed. However, contact Poison Control at 800-222-1222 if you’re uncertain about the amount taken or if you’re calling about a young child who got into the medication. You should call 911 if anyone experiences difficulty breathing, seizures, loss of consciousness, or severe uncontrollable agitation, though these reactions have not been reported even at doses many times higher than a double dose.
A Note on Montelukast’s Boxed Warning
You may have seen that montelukast carries an FDA boxed warning related to mood and behavior changes, including agitation, depression, anxiety, vivid dreams, confusion, difficulty sleeping, and in rare cases, suicidal thoughts. This warning applies to regular use of the medication at any dose, not specifically to overdose situations. A single accidental double dose is not expected to trigger these effects. But if you notice any unusual mood or behavioral changes over the days that follow, bring them up with your prescriber, as they may be related to the medication itself rather than the extra pill.