Sudafed (pseudoephedrine) is taken by mouth with water, typically every 4 to 6 hours for immediate-release tablets or every 12 hours for extended-release versions. The specific dose depends on which formulation you buy, so checking the box matters. Here’s what you need to know to take it correctly and safely.
Immediate-Release Tablets
The standard Sudafed tablet contains 30 mg of pseudoephedrine. Adults and children 12 and older take 2 tablets (60 mg) every 4 to 6 hours, with a maximum of 8 tablets in 24 hours. Children ages 6 to 11 take 1 tablet every 4 to 6 hours, up to 4 tablets per day. Children under 6 should not take pseudoephedrine.
You can take these tablets with or without food. Research on pseudoephedrine absorption shows that eating has minimal effect on how much of the drug your body uses, with bioavailability around 91% whether you’ve eaten or not. That said, taking it with a glass of water and a small snack can help if it bothers your stomach.
Extended-Release Tablets
Sudafed 12 Hour contains 120 mg of pseudoephedrine in a slow-release format. Take 1 tablet every 12 hours, with no more than 2 tablets in 24 hours. A 24-hour version delivers 240 mg and is taken once daily.
The critical rule with extended-release tablets: swallow them whole. Do not crush, break, or chew them. The tablet is designed to release the medication gradually. Breaking it dumps the full dose into your system at once, which increases side effects and raises blood pressure more than intended.
Timing It for Sleep
Pseudoephedrine is a stimulant. It raises heart rate by roughly 3 beats per minute on average and can make you feel wired, restless, or unable to fall asleep. If insomnia is a concern, take your last dose at least 4 to 6 hours before bedtime for the immediate-release version. For the 12-hour tablet, take your second dose in the early afternoon rather than right before bed.
Who Should Avoid Sudafed
Pseudoephedrine works by narrowing blood vessels, which is what shrinks swollen nasal tissue and opens your airways. But that same narrowing makes it harder for blood to flow, which can push blood pressure up. If you have severe or uncontrolled high blood pressure, skip pseudoephedrine entirely. For people whose high blood pressure is well controlled with medication, the increase is modest (about 1 mm Hg in systolic pressure on average), but it’s still worth discussing with your pharmacist if you take blood pressure medication.
One major drug interaction to know about: if you take or have recently taken an MAOI (a type of antidepressant), pseudoephedrine is off limits. The combination can cause a dangerous spike in blood pressure because both drugs amplify the same stimulating signals in your blood vessels. You need at least a 14-day gap after stopping an MAOI before taking pseudoephedrine.
Make Sure You’re Getting the Right Product
Most decongestants sitting on open pharmacy shelves contain phenylephrine, not pseudoephedrine. This matters because the FDA has determined that oral phenylephrine does not actually work as a nasal decongestant. An advisory committee reviewed the data and unanimously agreed it’s ineffective at standard over-the-counter doses. The FDA has proposed removing it from the market.
Real Sudafed (pseudoephedrine) is kept behind the pharmacy counter. You don’t need a prescription, but you do need to show a valid ID and sign a logbook. Federal law limits purchases to 3.6 grams per day and 9 grams over any 30-day period. In practical terms, a box of 24 standard 30 mg tablets contains 0.72 grams of pseudoephedrine, so these limits won’t affect a typical buyer picking up a box or two for a cold. The restrictions exist because pseudoephedrine can be chemically converted into methamphetamine.
Common Side Effects
Beyond the stimulant effects on sleep and heart rate, pseudoephedrine can cause dry mouth, mild anxiety, and occasional headaches. Higher doses and immediate-release formulations tend to produce stronger side effects than lower doses or extended-release versions. These effects are generally more pronounced in the first day or two of use and in shorter courses of treatment.
If you notice a racing heartbeat, significant jitteriness, or a pounding sensation in your chest, you’ve likely taken too much or you’re more sensitive to stimulant effects. Dropping to a lower dose or switching to the extended-release version, which delivers the drug more gradually, often helps.