The original Sudafed contains one active ingredient: pseudoephedrine hydrochloride, a compound that narrows swollen blood vessels in your nasal passages to relieve congestion. The standard immediate-release tablet delivers 30 or 60 mg of pseudoephedrine, while the 12-hour extended-release version contains 120 mg. Beyond that single decongestant, the rest of the tablet is made up of inactive ingredients that hold it together, coat it, and control how quickly it dissolves.
The Active Ingredient: Pseudoephedrine
Pseudoephedrine belongs to a class of drugs called sympathomimetic amines. It works by stimulating receptors on blood vessels inside your nose and sinuses, causing those vessels to constrict. When the blood vessels shrink, the swollen tissue around them shrinks too, opening your airways. The drug also triggers a small release of norepinephrine, one of your body’s natural “fight or flight” chemicals, which adds to the constricting effect. This is why pseudoephedrine can raise blood pressure and heart rate as a side effect.
For adults and children 12 and older, the standard dose is 60 mg every four to six hours, with a maximum of 240 mg in 24 hours. The 12-hour extended-release version delivers 120 mg in a single multilayer tablet designed to dissolve gradually. Children ages 6 to 11 take half the adult dose (30 mg), and children 4 to 5 take 15 mg.
Sudafed PE Uses a Different Drug
The version sold freely on pharmacy shelves, Sudafed PE, does not contain pseudoephedrine. Its active ingredient is phenylephrine, which targets the same type of receptors but has a major limitation: less than 1% of an oral dose actually reaches your bloodstream. Most of it gets broken down in your gut before it can do anything useful.
In clinical trials, pseudoephedrine consistently outperformed phenylephrine at relieving congestion. After six hours, people who took pseudoephedrine had measurably clearer nasal passages compared to those who took phenylephrine. In several studies, phenylephrine performed no better than a placebo. Even higher doses (up to 40 mg) didn’t improve results and only increased side effects. In 2023, an FDA advisory committee unanimously concluded that the scientific data do not support oral phenylephrine’s effectiveness as a nasal decongestant, and the FDA has proposed removing it from the approved list of over-the-counter decongestant ingredients.
Inactive Ingredients in Tablet Form
The active ingredient makes up only a small fraction of each tablet’s weight. The rest is a mix of structural and cosmetic ingredients that serve specific manufacturing purposes:
- Microcrystalline cellulose is the primary filler, adding bulk so the tablet is large enough to handle and swallow.
- Dibasic calcium phosphate dihydrate acts as another filler and helps the tablet hold its shape during compression.
- Magnesium stearate is a lubricant that prevents the powder from sticking to manufacturing equipment.
- Colloidal silicon dioxide keeps the powder flowing smoothly through the machines.
- Hypromellose and polyethylene glycol form the film coating on the outside of the tablet, making it easier to swallow and protecting the contents from moisture.
- Titanium dioxide gives the coating its white color.
- Polysorbate 80 helps distribute the coating ingredients evenly.
- Carnauba wax adds a final polish to the tablet surface.
In the 12-hour extended-release version, the tablet uses a multilayer design. Rather than releasing all 120 mg at once, the layers dissolve at different rates so the drug enters your system steadily over 12 hours.
Liquid Formulations Have More Additives
Children’s Sudafed comes as a liquid solution of pseudoephedrine hydrochloride, and its inactive ingredient list is longer than the tablet version. The liquid uses saccharin sodium and sorbitol as sweeteners, FD&C Blue No. 1 and FD&C Red No. 40 for color, and sodium benzoate as a preservative. Glycerin gives the liquid a smooth texture, menthol adds a cooling sensation, and citric acid helps balance the pH. Additional ingredients like povidone and poloxamer 407 act as stabilizers to keep everything uniformly mixed.
Why You Can’t Buy Original Sudafed Off the Shelf
Pseudoephedrine can be chemically converted into methamphetamine, which is why original Sudafed is kept behind the pharmacy counter in the United States. Under the Combat Methamphetamine Epidemic Act of 2005, you need a government-issued photo ID to purchase it. Federal law caps purchases at 3.6 grams of pseudoephedrine base per day and 9 grams per 30-day period. For context, a box of 24 immediate-release 30 mg tablets contains 0.72 grams total, so these limits are generous for anyone buying the product for congestion relief. This restriction is the reason Sudafed PE, with its freely available but far less effective phenylephrine formula, became so common on store shelves.