Amoxicillin comes in several different forms, and there’s also a combination version that pairs it with another ingredient to fight a wider range of bacteria. The core drug is the same across all of them, but the form you’re prescribed depends on the infection being treated, your age, and whether you can swallow pills.
Standard Forms: Capsules, Tablets, and Liquid
The most common versions of amoxicillin are capsules, tablets, and oral suspension (the liquid form). Capsules come in 250 mg and 500 mg strengths. Tablets come in 500 mg and 875 mg strengths. These are the forms most adults take, typically two or three times a day depending on the infection.
The oral suspension is a powder that gets mixed with water at the pharmacy, producing a flavored liquid. It’s available in four concentrations: 125 mg, 200 mg, 250 mg, and 400 mg per 5 mL (one teaspoon). The lower concentrations tend to be strawberry-flavored, while the higher ones are bubble-gum flavored. This is the go-to form for children, people who have trouble swallowing pills, or anyone who needs a flexible dose that doesn’t line up neatly with capsule sizes.
One practical difference worth knowing: the liquid form needs to be refrigerated (or at least kept at room temperature) and must be thrown away after 14 days. Capsules and tablets, by contrast, stay stable for much longer in a medicine cabinet. If you’re prescribed the liquid, plan to finish your course within that two-week window.
How the Forms Absorb in Your Body
For most people, tablets, capsules, and liquid amoxicillin all deliver the drug into your bloodstream at roughly the same rate. The body absorbs amoxicillin well regardless of the form, so your doctor’s choice between them usually comes down to convenience and the dose you need.
There is one notable exception. People who’ve had gastric bypass surgery absorb significantly less amoxicillin from tablets than from the liquid suspension. Research in the British Journal of Clinical Pharmacology found that tablets had both a slower absorption rate and lower overall drug levels in gastric bypass patients. The reason: after surgery, the stomach is much smaller and empties faster, so tablets don’t have enough time to fully dissolve before moving into the intestine. The liquid version skips that step entirely because the drug is already dissolved. If you’ve had weight-loss surgery, the liquid form is generally the better option.
Extended-Release Amoxicillin
There’s also an extended-release tablet, sold under the brand name Moxatag. It’s a 775 mg tablet designed to release the drug slowly over 24 hours, so you take it just once a day instead of two or three times. You need to take it within an hour of eating, and the tablets must be swallowed whole. Crushing or chewing them would dump the full dose at once, defeating the purpose of the slow-release design. This version is primarily used for throat infections caused by strep bacteria.
Amoxicillin-Clavulanate: The Combination Version
This is the type that often confuses people. Amoxicillin-clavulanate (brand name Augmentin) pairs standard amoxicillin with an additional ingredient called clavulanic acid. The amoxicillin does the bacteria-killing work. The clavulanic acid disables a defense mechanism that some bacteria use to break down amoxicillin before it can work. Certain strains of bacteria, particularly some that cause sinus infections, ear infections, and urinary tract infections, produce enzymes that chew up plain amoxicillin. Adding clavulanic acid blocks those enzymes, making the antibiotic effective against bacteria that would otherwise resist it.
The tradeoff is a higher rate of side effects. In a large study of adults treated for sinus infections, gastrointestinal problems like nausea and diarrhea were more common with the combination version. The difference was meaningful enough that for every 500 patients switched from amoxicillin-clavulanate to plain amoxicillin, one emergency visit for a gut-related side effect could be prevented. The combination was also linked to a small but real risk of a serious intestinal infection called C. difficile, which didn’t occur at all in the plain amoxicillin group. It’s also the most commonly prescribed antibiotic associated with drug-induced liver problems, though this remains rare.
Your doctor chooses between the two based on the type of infection and how likely it is that resistant bacteria are involved. For a straightforward strep throat, plain amoxicillin works well. For a bacterial sinus infection where resistant organisms are more likely, guidelines from the Infectious Diseases Society of America favor the combination version.
Injectable Amoxicillin
Amoxicillin is also available as an injection, though this form is far more common outside the United States. In the UK and other countries, it’s used in hospitals when a patient can’t take medication by mouth, delivered either directly into a vein over 3 to 4 minutes or through a slow drip over 20 to 30 minutes. Intramuscular injection (into muscle tissue) is reserved for situations where IV access isn’t possible. The injectable form is not widely marketed in the U.S., where doctors typically switch to other IV antibiotics in the same drug family when oral amoxicillin isn’t an option.
How Amoxicillin Compares to Penicillin
People sometimes wonder whether amoxicillin is just another name for penicillin. It’s in the same antibiotic family, but amoxicillin covers a broader range of bacteria. Standard penicillin V (the oral form) works well against the specific bacteria that cause strep throat and certain skin infections, but amoxicillin also reaches some gut-dwelling bacteria that penicillin can’t touch. That broader reach is why amoxicillin is prescribed more often for ear infections, urinary tract infections, and respiratory infections. The flip side of that broader coverage: amoxicillin is more likely than penicillin V to disrupt normal gut bacteria, occasionally leading to yeast overgrowth or, rarely, C. difficile infection.
For strep throat specifically, both drugs work. The CDC recommends amoxicillin at up to 1,000 mg once daily or 500 mg twice daily for 10 days. Penicillin V is dosed at 500 mg twice daily for the same duration. Amoxicillin is often preferred for children simply because the flavored liquid is easier to take than penicillin’s less palatable options.