The main active ingredient in original Sudafed is pseudoephedrine hydrochloride, a decongestant that shrinks swollen blood vessels in your nasal passages to relieve stuffiness. A standard tablet contains 30 mg or 60 mg of pseudoephedrine, though extended-release versions pack 120 mg or 240 mg into a single dose. But “Sudafed” now appears on several different products with different formulas, so what you’re actually getting depends on which box you pick up.
How Pseudoephedrine Works
Pseudoephedrine triggers the release of norepinephrine, a chemical your body naturally uses to tighten blood vessels. When the blood vessels lining your nose and sinuses constrict, the swollen tissue shrinks, mucus production drops, and air flows more freely. This is why it works for nasal congestion from colds, flu, sinusitis, and allergies.
The effect is systemic, meaning it reaches your nasal passages through your bloodstream after you swallow the tablet. That’s different from nasal sprays, which act locally. It also means pseudoephedrine can raise blood pressure and heart rate slightly, which is why people with high blood pressure, heart disease, or an overactive thyroid should avoid it.
Sudafed PE Uses a Different Ingredient
If you grabbed a box labeled “Sudafed PE” off the regular pharmacy shelf, you got phenylephrine hydrochloride (5 mg per tablet) instead of pseudoephedrine. Phenylephrine is also a decongestant, but it works differently and has a much harder time surviving digestion. In 2023, an FDA advisory panel concluded that oral phenylephrine is no more effective than a placebo at standard doses. Many pharmacies still sell it, but it’s not the same formula that gave Sudafed its reputation.
The key difference at the store: original Sudafed with pseudoephedrine is kept behind the pharmacy counter, while Sudafed PE sits on the open shelf. If you want the version with pseudoephedrine, you need to ask a pharmacist and show ID.
Combination Formulas
Sudafed sells several multi-symptom products that pair pseudoephedrine with other active drugs. Sudafed Sinus 12 Hour Pressure + Pain, for example, contains 120 mg of pseudoephedrine alongside 220 mg of naproxen sodium (the same pain reliever in Aleve). Other combination products add acetaminophen for pain and fever, or guaifenesin to loosen chest mucus. Always check the “Active Ingredients” panel on the box, because doubling up on pain relievers you’re already taking separately is a common and avoidable mistake.
Inactive Ingredients in the Tablets
Beyond the active drug, each Sudafed tablet contains a list of inactive ingredients that hold it together, control how quickly it dissolves, and give it color. The standard Sudafed Sinus Congestion tablet includes carnauba wax, microcrystalline cellulose, magnesium stearate, pregelatinized starch, and several dyes (D&C Yellow No. 10, FD&C Red No. 40, FD&C Yellow No. 6). It also contains hypromellose, polyethylene glycol, polyvinyl alcohol, talc, and titanium dioxide as coating agents. None of these are pharmacologically active, but they matter if you have sensitivities to specific dyes or fillers.
Dosing Limits
For adults and children 12 and older, the standard dose is 60 mg every four to six hours, with a hard ceiling of 240 mg in 24 hours. Extended-release tablets are taken as 120 mg every 12 hours or 240 mg once daily. Children ages 6 to 11 take half the adult dose (30 mg per dose, 120 mg max daily), and kids 4 to 5 take 15 mg per dose with a 60 mg daily max. Children under 4 should not take pseudoephedrine at all.
Why It’s Behind the Counter
Pseudoephedrine can be chemically converted into methamphetamine, which is why the Combat Methamphetamine Epidemic Act of 2005 placed strict limits on its sale. You can buy no more than 3.6 grams of pseudoephedrine per day and no more than 9 grams in a 30-day period. That works out to roughly a 15-day supply of regular-strength tablets per month. Purchases are logged electronically, and you must present a valid photo ID. A few states, including Oregon and Mississippi, require an actual prescription.
Who Should Avoid Sudafed
Pseudoephedrine is not safe for everyone. Because it constricts blood vessels body-wide, it can worsen high blood pressure, heart disease, glaucoma, and hyperthyroidism. It can also aggravate an enlarged prostate by tightening muscles around the bladder. People with diabetes, or liver or kidney problems, should check with a pharmacist before using it. One important interaction: if you’ve taken a type of antidepressant called an MAOI in the last two weeks, pseudoephedrine can cause a dangerous spike in blood pressure.