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Amoxicillin: 13 Burning Questions

Medically reviewed by L. Anderson, PharmD. Last updated on Aug 9, 2018.

1. Is Amoxicillin A Penicillin-Type Drug?

Amoxicillin is a common prescription antibiotic and one you have probably been prescribed. You know it: that pink suspension with a faint fruity smell you keep in the fridge, or those rather large tablets or capsules. It's a safe and useful drug with a long history, but nonetheless, there are specifics you should know before you embark on treatment.

How does it work? Amoxicillin, a member of the common aminopenicillin antibiotic class, acts as a beta-lactam antibiotic and kills bacteria by interfering with their cell wall growth. Ampicillin is also an aminopenicillin.

All beta-lactam antibiotics share a common structure in their chemistry called a beta-lactam ring. Penicillin-type drugs are a major breakthrough in the history of medicine, and are still widely used today.

2. Which Infections Can Amoxicillin Treat?

Amoxicillin is used alone or in combination for a variety of bacterial infections, which might include:

3. How Does Amoxicillin Come At the Pharmacy?

You may have received amoxicillin as a capsule, chewable tablet, or oral suspension at the pharmacy.

Amoxicillin (Moxatag) also comes in an extended-release tablet form taken only once per day for a painful strep throat.

Amoxicillin is also often prescribed in combination with the beta-lactamase inhibitor clavulanate (Augmentin) in an oral liquid suspension or tablet form. Beta-lactamase inhibitors help to prevent resistance and make the amoxicillin more effective. Amoxicillin/clavulanate also comes in chewable tablets and extended-release forms.

Kids will be happy that the suspension flavors include banana, orange, strawberry, and fruit, to make the medicine go down a little easier.

Isn't Resistance A Problem With Amoxicillin?

If you've received a prescription for amoxicillin with clavulanate (Augmentin), you may wonder why you need this extra added agent "clavulanate"? Clavulanate is a beta-lactamase inhibitor, and it works by preventing bacteria from destroying the active ingredient amoxicillin.

Some bacteria produce a beta-lactamase enzyme, which can cleave the beta-lactam chemical structure in antibiotics like penicillin or amoxicillin.

To fight resistance, beta-lactamase inhibitors like clavulanate are given with beta-lactam antibiotics to block the action of the beta-lactamase enzyme. Clavulanate given by itself is not effective as an antibiotic.

5. Can I Take Amoxicillin If I'm Allergic to Penicillin?

Allergy to penicillin is the most commonly reported drug allergy. You should not take amoxicillin if you are truly allergic to any penicillin antibiotic, such as ampicillin, oxacillin, or penicillin.

However, in one study, most patients who reported a penicillin allergy were not truly allergic. Certain allergies (such as anaphylaxis) can be life-threatening, while others may result in only a minor rash. In addition, in children, a rash may occur with certain infections around the same time the antibiotic is prescribed, and can be falsely attributed to the pencillin-type drug.

Report any allergy you have had to any medication, vitamin, inactive ingredient, or herbal supplement to your doctor. In situations where your treatment options are limited, or amoxicillin is the best or only option, an allergist may be able to perform oral or skin testing to determine if you are truly allergic to penicillin as a class.

6. Should I Avoid Alcohol When Taking Amoxicillin?

It is common to see an "Avoid Alcohol" label on prescription antibiotic bottles. This is not always because there may be a specific interaction between alcohol and the antibiotic, although there may be (see Table 1). Drinking alcohol while fighting an infection can also lead to dehydration and may hinder the body’s natural ability to heal itself.

Many over-the-counter medications (OTCs), such as cough or cold syrups may also contain alcohol in the formulation. In general, most (but not all) antibiotics can be taken safely with small amounts of alcohol, but it's probably better to skip the drink until you've finished your antibiotic and you're feeling all better.

7. Will Amoxicillin Break My Bank?

In general, amoxicillin is very affordable.

Most brand names of the drug are no longer marketed in the U.S. and generics are the norm. In fact, certain pharmacies in the U.S. may even have some strengths of the generic antibiotic for free or at a $4 cost, although many of these low cost programs are now being discontinued. Nonetheless, the cost for amoxicillin should still be reasonable. Pricing is always variable, so check with your pharmacy directly. The pink oral suspension that is so often used in children should also be very inexpensive.

If you have insurance, you may find that the cash price without using insurance is cheaper than your copay, so be sure to ask your pharmacist. In fact, this may be the case for many generic drugs you buy, so double check. Discount coupons can be helpful, too.

8. I Have a Cold. Why Can't I Get an Antibiotic?

Many infections are caused by viruses, not bacteria. The common cold, the flu, sinusitis, and even most sore throats are viral in nature, and antibiotics simply do not work to kill viruses. Most viral illnesses do not need special medication and are “self-limiting”, meaning your own immune system can fight off the illness.

Improper use of antibiotics to treat viral infections is leading to an epidemic of antibiotic resistance, and today doctors are very careful not to prescribe antibiotics when they are not needed. Not only will this worsen the resistance epidemic, it will also put you at risk for unnecessary side effects and drug costs. There is no reason to demand an antibiotic when you simply don't need it.

9. How Do I Use Amoxicillin?

Be sure to complete all of your medicine, even if you feel 100% better (unless otherwise directed by your doctor). You can develop antibiotic resistance if you do not finish all of your medication, not to mention you won't get better. You can take most forms of amoxicillin with food if it causes you an upset stomach.

  • Amoxicillin and clavulanate (Augmentin) should be taken with food or milk, and Moxatag extended-release (ER) tablet and other high-dose amoxicillins should be taken within 1 hour of a meal.
  • Be sure not to crush, cut or chew the ER tablets; you want to maintain the ER matrix within the tablet to allow the antibiotic to disperse over time.
  • Shake the oral suspensions well, and keep refrigerated, if recommended on the label.
  • Go here to find general dosing information for your speicifc antibiotic.

10. Does Amoxicillin Lower the Effectiveness of Hormonal Contraceptives?

There is no evidence that extra birth control measures are needed with antibiotics unless you are taking the antibiotic rifampin or rifabutin. Rifampin treats tuberculosis and rifabutin is used for Mycobacterium avium complex (MAC) infection in those with HIV. Other antibiotics have not been shown to make the pill less effective; however, some prescribers may still recommend that you use an added method of birth control (condom) to your hormonal method during and for one week after antibiotic treatment.

According to Columbia University, some women who experience irregular periods, diarrhea, vomiting, or stomach disorders when taking antibiotics may also want to consider using back-up options, like a condom, as these factors may lower the effectiveness of hormonal birth control. A few other medications may also lower the effectiveness of birth control. Always have your pharmacist run a drug interaction screen any time you start or stop a prescription medication, herbal supplement, or any over-the-counter drug.

Remember, birth control pills fail at least 1% of the time even in ideal conditions. According to Planned Parenthood, "the main thing that makes the pill not work is not taking it every day." See Planned Parenthood for more information.

11. What About Side Effects With Amoxicillin?

In general, amoxicillin is tolerated very well. However, some patients do have stomach upset, nausea, vomiting or diarrhea when using amoxicillin.

A probiotic taken with the amoxicillin may help to decrease the occurrence of loose stools if this is common for you with antibiotic treatment. Some reactions can be rare, but serious, and if you have any of these amoxicillin side effects be sure to contact a healthcare provider immediately:

12. Is It One Dose Fits All?

The usual adult dose range for amoxicillin is 250 to 500 milligrams (mg) every 8 hours, or 500 to 875 mg every 12 hours, or one 775 mg extended-release tablet once daily. Your doctor may adjust these doses based on your specific infection or if you have reduced kidney function.

The extended-release and high dose amoxicillin forms should be avoided if you have severe kidney impairment. Risk factors for chronic kidney disease include:

  • diabetes
  • high blood pressure
  • heart disease
  • smoking
  • obesity
  • high cholesterol
  • age over 65
  • being African-American, Native American or Asian-American
  • a family history of kidney disease

13. Amoxicillin: Is It Safe in Pregnancy and Breastfeeding?

Your doctor and your baby's pediatrician should always have the final say on any medication you use during pregnancy or breastfeeding. However, in general, amoxicillin is considered safe in both situations if a women needs an antibiotic during pregnancy or breastfeeding, and the doctor feels that the benefit outweighs the risk to mother and baby.

Amoxicillin is also considered acceptable while nursing; however, rash, diarrhea or thrush -- a yeast infection of your infant's mouth -- may occur infrequently, so double check with your pediatrician if you have concerns.

Bottom Line on Amoxicillin Use

Amoxicillin is a safe and affordable antibiotic; however, it is not the right antibiotic for all infections. It is important not to share your antibiotics with anyone. An antibiotic is prescribed specifically for you and your particular type of bacterial infection.

When you receive an antibiotic at the pharmacy, take the time to review the directions and warning labels. If you have phenylketonuria PKU, talk with your doctor. Some amoxicillin products may contain phenylalanine. Follow your doctor's directions and finish all of your medication, even when you feel completely well.

Finally, don't demand an antibiotic from your doctor if you have a viral infection, like a cold or flu -- they simply don't work and may even worsen your virus. Rest, drink plenty of fluids, and allow your body the time to heal and utilize your own immune system.

Finished: Amoxicillin: 13 Burning Questions

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  • Up to Date. Beta-lactam antibiotics: Mechanisms of action and resistance and adverse effects. Accessed August 9, 2018 at
  • Mayo Clinic. Birth Control. Accessed August 9, 2018 at
  • Columbia University Health. Go Ask Alice. Antibiotic and the Birth Control Pill. August 9, 2018 at
  • Up to Date. Overview of the use of estrogen-progestin contraceptives. Drug Interactions. Accessed August 9, 2018 at
  • Think You're Allergic to Penicillin? Maybe Not. Accessed August 9, 2018 at
  • Bedsider. Which medications can mess with birth control? Accessed August 9, 2018 at
  • Drawz S, Bonomo R. Three Decades of β-Lactamase Inhibitors. Clin Microbiol Rev. 2010 Jan; 23(1): 160–201. Accessed August 9, 2018 at

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