Skip to content
Font Size

Antiprotozoals for Giardiasis


Generic Name Brand Name
albendazole Albenza
metronidazole Flagyl
nitazoxanide Alinia
tinidazole Tindamax

Albendazole is taken as a tablet.

Metronidazole comes in tablet and liquid forms. It usually is taken in tablet form for 3 to 7 days for treatment of giardiasis.

Nitazoxanide comes as tablets and as a liquid.

Paromomycin comes as a capsule. It is usually taken several times a day for 5 to 10 days.

Tinidazole comes in tablet form. It usually is taken for 1 day either in one dose or in several doses throughout the day.

How It Works

These medicines kill Giardia lamblia in the digestive tract.

Why It Is Used

These medicines are used to treat certain bacterial and parasite infections. They also are an effective treatment for giardiasis infection.

These medicines may be used if stool analysis or other testing shows giardiasis infection is present.

If your doctor thinks that your symptoms are caused by giardia, he or she may prescribe one of these medicines even before your test results are back.

How Well It Works

Albendazole cures giardiasis 62% to 95% of the time.1

Metronidazole and tinidazole cures giardiasis in adults 80% to 95% of the time.2, 3

Nitazoxanide is successful for treating giardiasis 65% to 85% of the time.2 It is often used to treat giardiasis in children.

Paromomycin cures giardiasis 50% to 70% of the time.4

Side Effects

All medicines have side effects. But many people don't feel the side effects, or they are able to deal with them. Ask your pharmacist about the side effects of each medicine you take. Side effects are also listed in the information that comes with your medicine.

Here are some important things to think about:

  • Usually the benefits of the medicine are more important than any minor side effects.
  • Side effects may go away after you take the medicine for a while.
  • If side effects still bother you and you wonder if you should keep taking the medicine, call your doctor. He or she may be able to lower your dose or change your medicine. Do not suddenly quit taking your medicine unless your doctor tells you to.

Call911or other emergency services right away if you have:

Call your doctor right away if you have:

  • Hives.
  • Numbness, tingling, pain, or weakness in your hands or feet.

Common side effects of these antiprotozoals include:

Metronidazole and tinidazole

Do not drink alcohol while you are taking metronidazole or tinidazole. Drinking alcohol while you are taking these medicines can cause headaches, nausea, reddening of the face, belly cramps, and vomiting. You should also avoid alcohol for at least 3 days after you finish your last dose of these medicines.


Long-term use of nitazoxanide can cause the whites of the eyes to turn yellow. But the yellow color goes away after use of this medicine is stopped.

See Drug Reference for a full list of side effects. (Drug Reference is not available in all systems.)

What To Think About

Taking medicine

Medicine is one of the many tools your doctor has to treat a health problem. Taking medicine as your doctor suggests will improve your health and may prevent future problems. If you don't take your medicines properly, you may be putting your health (and perhaps your life) at risk.

There are many reasons why people have trouble taking their medicine. But in most cases, there is something you can do. For suggestions on how to work around common problems, see the topic Taking Medicines as Prescribed.

Advice for women


Do not use this medicine if you are pregnant or planning to get pregnant. If you need to use this medicine, talk to your doctor about how you can prevent pregnancy.

Metronidazole and tinidazole

These medicines are not used for pregnant women during the first trimester of pregnancy. If you are pregnant or planning to get pregnant, do not use any medicines unless your doctor tells you to. Some medicines can harm your baby. This includes prescription and over-the-counter medicines, vitamins, herbs, and supplements. And make sure that all your doctors know that you are pregnant or planning to get pregnant.

Nitazoxanide and paromomycin

If you are pregnant, breast-feeding, or planning to get pregnant, do not use any medicines unless your doctor tells you to. Some medicines can harm your baby. This includes prescription and over-the-counter medicines, vitamins, herbs, and supplements. And make sure that all your doctors know that you are pregnant, breast-feeding, or planning to get pregnant.


Follow-up care is a key part of your treatment and safety. Be sure to make and go to all appointments, and call your doctor if you are having problems. It's also a good idea to know your test results and keep a list of the medicines you take.

Complete the new medication information form (PDF)(What is a PDF document?) to help you understand this medication.


  1. Hoque ME (2013). Giardiasis. In ET Bope, RD Kellerman, eds., Conn's Current Therapy 2013, pp. 100–103. Philadelphia: Saunders.

  2. Hill DR, Nash TE (2010). Giardia lamblia. In GL Mandell et al., eds., Mandell, Douglas, and Bennett's Principles and Practice of Infectious Disease, 7th ed., vol. 2, pp. 3527–3534. Philadelphia: Churchill Livingstone Elsevier.

  3. Rosenthal PJ (2010). Protozoal and helminthic infections. In SJ McPhee, MA Papadakis, eds., 2010 Current Medical Diagnosis and Treatment, 49th ed., pp. 1348–1389. New York: McGraw-Hill Medical.

  4. American Academy of Pediatrics (2009). Giardia intestinalis infections (giardiasis). In LK Pickering et al., eds., Red Book: 2009 Report of the Committee on Infectious Diseases, 28th ed., pp. 303–305. Elk Grove Village, IL: American Academy of Pediatrics.

By Healthwise Staff
Primary Medical Reviewer E. Gregory Thompson, MD - Internal Medicine
Specialist Medical Reviewer W. David Colby IV, MSc, MD, FRCPC - Infectious Disease
Current as of August 8, 2013

WebMD Medical Reference from Healthwise

Last Updated: August 08, 2013
This information is not intended to replace the advice of a doctor. Healthwise disclaims any liability for the decisions you make based on this information.

Hot Topics

WebMD Video: Now Playing

Click here to wach video: Dirty Truth About Hand Washing

Which sex is the worst about washing up? Why is it so important? We’ve got the dirty truth on how and when to wash your hands.

Click here to watch video: Dirty Truth About Hand Washing

Popular Slideshows & Tools on WebMD

disciplining a boy
Types, symptoms, causes.
What it looks like.
fruit drinks
Eat these to think better.
No gym workout
Moves to help control blood sugar.
acupuncture needle on shoulder
10 tips to look and feel good.
Close up of eye
12 reasons you're distracted.
Epinephrine Injection using Auto-Injector Syringe
Life-threatening triggers.
woman biting a big ice cube
Habits that wreck your teeth.
embarrassed woman
Do you feel guilty after eating?
pacemaker next to xray
Treatment options.
caregiver with parent
10 tips for daily life.
birth control pills
Which kind is right for you?

Pollen counts, treatment tips, and more.

It's nothing to sneeze at.

Loading ...

Sending your email...

This feature is temporarily unavailable. Please try again later.


Now check your email account on your mobile phone to download your new app.

Women's Health Newsletter

Find out what women really need.