Hesperian Health Guides
The Healthwiki provides free information to 20,000 people every day.
This is made possible by donors like you!
Make a gift to support this essential health information people depend on.
Antibiotics are medicines that fight infection from bacteria. They do not help against viral infections like chicken pox, rubella, flu, or the common cold. Not all antibiotics will fight all infections from bacteria. Antibiotics that share the same chemical make-up are said to be from the same family. It is important to know about the families of antibiotics for 2 reasons:
- Antibiotics from the same family can often treat the same problems. This means you can use a different medicine from the same family.
- If you are allergic to an antibiotic of one family, you will also be allergic to the other members of the same family of antibiotics. This means you will have to take a medicine from another family instead.
Antibiotics must be given for their full “course.” Stopping before you have finished all the days of treatment, even if you feel better, can make the infection return in a form that is even harder to stop.
Ampicillin and Amoxicillin
Ampicillin and amoxicillin are broad-spectrum penicillins, which means they kill a wide-range of bacteria. The two are often interchangeable. When you see a recommendation for ampicillin in this book, you will often be able to use amoxicillin in its place, in the correct dose (see below).
Ampicillin and amoxicillin are very safe and are especially useful for babies and small children. When combined with other medicines, ampicillin is useful for ulcers and for peritonitis.
Both these medicines, but especially ampicillin, tend to cause nausea and diarrhea. Avoid giving them to people who already have diarrhea, if you can give another antibiotic instead.
The other common side effect is rash. Raised, itchy bumps that come and go in a few hours are probably a sign of penicillin allergy. Stop giving the medicine right away and do not give the person a penicillin medicine again. Future allergic reactions may be more severe and even life-threatening. For some problems erythromycin can be used instead. A flat rash that looks like measles, and usually starts a week after starting the medicine and takes days to go away, is not necessarily an allergy. But it is impossible to know for sure if the rash is from allergy or not, so it is usually better to stop the medicine.
Resistance to these medicines is growing more common. Depending on where you live, they may not work any more against staphylococcus, shigella, or other infections.
Below we list doses to give amoxicillin orally, and ampicillin orally and by injection. When possible, give amoxicillin by mouth. Use ampicillin by injection for severe illnesses, or when someone is vomiting or cannot swallow.
As with other antibiotics, how long to give them can vary for many reasons. But the general rule is to continue the medicine until all signs of infection (including fever) have been gone for at least 24 hours. For people with HIV, give the medicine for the full number of days listed. Likewise there is a range for how much to give. In general, give the lower amount of the range for a thinner person or for less severe infection, and the higher amount for a fatter person or more severe infection.AMOXICILLIN (ORAL)
dose by age:
Under 3 months: give 125 mg, 2 times a day for 7 to 10 days.
3 months to 3 years: give 250 mg, 2 times a day for 7 to 10 days.
4 to 7 years: give 375 mg, 2 times a day for 7 to 10 days.
8 to 12 years: give 500 mg, 2 times a day for 7 to 10 days.
Over 12 years: give 500 to 875 mg, 2 times a day for 7 to 10 days.
Continue giving amoxicillin until all signs of infection have been gone for at least 24 hours.AMPICILLIN (ORAL)
Under 1 year: give 100 mg, 4 times a day for 7 days.
1 to 3 years: give 125 mg, 4 times a day for 7 days.
4 to 7 years: give 250 mg, 4 times a day for 7 days.
8 to 12 years: give 375 mg, 4 times a day for 7 days.
Over 12 years: give 500 mg, 4 times a day for 7 days.
Continue giving ampicillin until all signs of infection have been gone for at least 24 hours.
Ampicillin can also be given by injection, but should be injected only for severe illnesses, or when someone is vomiting or cannot swallow.
dose by age:
Under 1 year: inject 100 mg, 4 times a day for 7 days.
1 to 5 years: inject 300 mg, 4 times a day for 7 days.
6 to 12 years: inject 625 mg, 4 times a day for 7 days.
Over 12 years: inject 875 mg, 4 times a day for 7 days.
Erythromycin works against many of the same infections as penicillin or tetracycline, and it can be used by people who are allergic to penicillins.
Erythromycin often causes nausea and diarrhea, especially in children. Do not use for more than 2 weeks as it may cause jaundice.
Newborns: give 65 mg, 2 times a day for 7 to 10 days.
Under 3 years: give 125 mg, 3 times a day for 7 to 10 days.
3 to 7 years: give 250 mg, 3 times a day for 7 to 10 days.
Over 8 years: give 250 to 500 mg, 4 times a day for 7 to 10 days.
For severe infections, double the doses above.
For cholera (where erythromycin works for cholera)
Tetracycline and Doxycycline
Tetracycline and doxycycline are broad-spectrum antibiotics that fight many different kinds of bacteria. They work well when given by mouth (and are very painful when injected, so they should not be given that way). There is a lot of resistance to these medicines, but they are still useful for fighting some infections.
Doxycycline and tetracycline can be used interchangeably. But doxycycline is usually a better choice because less is needed each day and it has fewer side effects.
Heartburn, stomach cramps, diarrhea, and yeast infections are common.
- Pregnant women should not take these medicines, because they can damage or stain the baby’s teeth and bones. For the same reason, children under 8 years old should take them only when there is no other effective antibiotic, and for short periods only. You can usually use erythromycin instead.
- Do not use tetracycline or doxycycline that is ‘‘old’’ or past its expiration date.
- Some people may sunburn quickly or get a skin rash after spending time in the sun while taking these medicines, so stay out of the sun or wear a large hat.
- These medicines may make birth control pills less effective. If possible use another method (such as condoms) while taking these medicines.
Avoid milk, iron pills, and antacids for 2 hours before or after taking tetracycline. They will make the medicine less effective. Take tetracycline on an empty stomach with plenty of water at least 1 hour before or 2 hours after meals.
8 to 12 years: give 125 mg, 4 times a day for 7 to 10 days.
Over 12 years: give 250 mg, 4 times a day for 7 to 10 days.
For cholera (where tetracycline works against cholera)
Over 12 years: give 500 mg, 4 times a day for 3 days.
Doxycycline is taken twice a day (instead of 4 times a day like tetracycline).
Avoid iron pills, and antacids for 2 hours before or after taking Doxycycline. They will make the medicine less effective.
Take doxycycline with plenty of water. It may be taken with food or milk if it upsets your stomach.
8 to 12 years: give 50 mg per dose for 7 to 10 days.
Over 12 years: give 100 mg per dose for 7 to 10 days.
For cholera (where doxycycline works against cholera)
8 to 12 years: give 150 mg, one time only.
Over 12 years: give 300 mg, one time only.
Metronidazole is used to treat gut infections caused by amebas, giardia, and certain bacteria.
Nausea, cramps, and diarrhea are common. Taking with food may help. Sometimes it causes a metallic taste in the mouth or a headache.
Do not give in the first 3 months of pregnancy. It may cause birth defects. Also avoid giving metronidazole later in pregnancy, and while breastfeeding unless it is the only effective medicine and is definitely needed. Do not drink alcohol while taking metronidazole and for 2 days after you finish taking it. Drinking alcohol while taking metronidazole causes severe nausea. Do not use metronidazole if you have liver problems.
For many problems, you can give a high dose of this medicine for 3 days, or a lower dose for 5 to 10 days. Pregnant women should avoid the high dose treatments.
Under 3 years: give 62 mg (¼ of a 250 mg tablet), 2 times a day for 5 days.
3 to 7 years: give 62 mg, 3 times a day for 5 days.
8 to 12 years: give 125 mg, 3 times a day for 5 to 7 days.
Over 12 years: give 250 mg, 3 times a day for 5 to 7 days. OR
Give 2 grams, once a day for 3 days.
Under 3 years: give 62 mg (¼ of a 250 mg tablet), 3 times a day for 8 to 10 days.
3 to 7 years: give 125 mg, 3 times a day for 8 to 10 days.
8 to 12 years: give 250 mg, 3 times a day for 8 to 10 days.
Over 12 years: give 500 to 750 mg, 3 times a day for 8 to 10 days.
After the last dose of metronidazole, take diloxanide furoate.For peritonitis or appendicitis
Ciprofloxacin is a broad spectrum antibiotic of the quinolone family. It works against a lot of different infections of the skin, bones, digestive tract, and urinary tract (bladder). But there is resistance to ciprofloxacin in many parts of the world, so use it only against the infections for which it is specifically recommended in your area. It is not a good antibiotic for children.
Nausea, diarrhea, vomiting, headache, dizziness, rash, or yeast infections.
Do not use if you are pregnant or breastfeeding. Do not take with dairy products.
Rarely, ciprofloxacin damages the tendons. Except for a few specific situations, it should not be given to children under 16 because their tendons are still developing. If you have pain in your calves when taking this medicine, stop taking it immediately.
Ceftriaxone is a strong antibiotic used against serious infections and for infections resistant to penicillin. Only use ceftriaxone to treat the specific infections for which it is recommended in your area. This will help prevent resistance and keep this drug useful.
Can be painful to inject. Mix with 1% lidocaine if you know how.
Do not give to a baby less than 1 week old. Do not use if there is jaundice.
Ceftriaxone cannot be taken by mouth. When injecting, put the needle deep in the muscle.
For severe infection
The doses are different depending on the infection, but in general you can give 50 to 100 mg per kg in children, and 1 to 4 grams in adults, once or twice a day.
1 week to 3 years: inject 250 mg, once a day for 5 days.
3 to 7 years: inject 500 mg, once a day for 5 days.
8 to 12 years: inject 1000 mg, once a day for 5 days.
Over 12 years: inject 1 to 2 grams, once a day for 5 days.