Cephalexin is an antibiotic that belongs to the family of medications known as cephalosporins. It is used to treat certain types of bacterial infections. Cephalexin is most often used to treat infections of the throat, skin, ear, bladder, respiratory tract, and bone. It works by killing the bacteria causing the infection.

This medication may be available under multiple brand names and/or in several different forms. Any specific brand name of this medication may not be available in all of the forms or approved for all of the conditions discussed here. As well, some forms of this medication may not be used for all of the conditions discussed here.

Your doctor may have suggested this medication for conditions other than those listed in these drug information articles. If you have not discussed this with your doctor or are not sure why you are taking this medication, speak to your doctor. Do not stop taking this medication without consulting your doctor.

Do not give this medication to anyone else, even if they have the same symptoms as you do. It can be harmful for people to take this medication if their doctor has not prescribed it.

The recommended adult dose of cephalexin ranges from 250 mg to 1,000 mg 4 times daily. It can be taken with food or on an empty stomach.

The usual dose of cephalexin for children is based on body weight. The recommended dose is 25 mg to 50 mg per kilogram of body weight each day, divided into 4 equal doses.

Many things can affect the dose of a medication that a person needs, such as body weight, other medical conditions, and other medications. If your doctor has recommended a dose different from the ones listed here, do not change the way that you are taking the medication without consulting your doctor.

Although it may be absorbed more quickly if it is taken on an empty stomach, cephalexin may be taken with food or on an empty stomach. The overall effect is not changed by taking it with food.

The liquid form of this medication should be measured accurately with a medication spoon or oral syringe, as these are more accurate than household measuring spoons. Shake the bottle of medication well before measuring each dose.

Finish all of this medication, even you start to feel better. This will reduce the chance of the infection returning.

It is important to take this medication exactly as prescribed by your doctor. If you miss a dose, take it as soon as possible and continue with your regular schedule. If it is almost time for your next dose, skip the missed dose and continue with your regular dosing schedule. Do not take a double dose to make up for a missed one. If you are not sure what to do after missing a dose, contact your doctor or pharmacist for advice.

Store the liquid form of this medication in the refrigerator for up to 14 days.  Do not freeze. The tablets should be stored at room temperature, protected from light and moisture. Keep this medication out of the reach of children.

Do not take this medication if you:

• are allergic to cephalexin, or any ingredients of the medication
• are allergic to any other cephalosporin antibiotics

Many medications can cause side effects. A side effect is an unwanted response to a medication when it is taken in normal doses. Side effects can be mild or severe, temporary or permanent. The side effects listed below are not experienced by everyone who takes this medication. If you are concerned about side effects, discuss the risks and benefits of this medication with your doctor.

The following side effects have been reported by at least 1% of people taking this medication. Many of these side effects can be managed, and some may go away on their own over time.

Contact your doctor if you experience these side effects and they are severe or bothersome. Your pharmacist may be able to advise you on managing side effects.

• agitation
• diaper rash
• dizziness
• fatigue
• headache
• mild diarrhea
• mild stomach cramps
• nausea
• vaginal itching or discharge
• vomiting

Although most of these side effects listed below don't happen very often, they could lead to serious problems if you do not check with your doctor or seek medical attention.

Check with your doctor as soon as possible if any of the following side effects occur:

• abdominal tenderness
• behaviour changes in young children
• confusion
• hallucinations (seeing or hearing things that aren't there)
• hearing loss (young children)
• ringing in the ears
• sensation of spinning
• severe abdominal or stomach cramps and pain
• signs of liver problems (e.g., nausea, vomiting, diarrhea, loss of appetite, weight loss, yellowing of the skin or whites of the eyes, dark urine, pale stools)
• skin rash, itching, redness, or swelling

Stop taking the medication and seek immediate medical attention if any of the following occur:

• diarrhea (watery and severe; may also be bloody)
• signs of a serious allergic reaction (e.g., abdominal cramps, difficulty breathing, nausea and vomiting, or swelling of the face and throat)
• signs of a severe skin reaction (e.g., blistering, peeling, a rash covering a large area of the body, a rash that spreads quickly, or a rash combined with fever or discomfort)

Some people may experience side effects other than those listed. Check with your doctor if you notice any symptom that worries you while you are taking this medication.

Before you begin using a medication, be sure to inform your doctor of any medical conditions or allergies you may have, any medications you are taking, whether you are pregnant or breast-feeding, and any other significant facts about your health. These factors may affect how you should use this medication.

Allergy: Some people who are allergic to penicillin antibiotics also experience allergic reactions to cephalosporins, including cephalexin. Before you take cephalexin, tell your doctor about any previous adverse reactions you have had to medications, especially cephalosporins and penicillins. Contact your doctor at once if you experience signs of an allergic reaction, such as skin rash, itching, difficulty breathing, or swelling of the face and throat.

Other hypersensitivity reactions involving the skin and other organs have also been reported with the use of other, similar antibiotics. Stop taking the medication and get immediate medical attention if you have symptoms of a severe allergic reaction, including fever, swollen glands, yellowing of the skin or eyes, or flu-like symptoms with skin rash or blistering.

Antibiotic-associated colitis: This medication, like other antibiotics, may cause a potentially dangerous condition called antibiotic-associated colitis (or pseudomembranous colitis). Symptoms include severe, watery diarrhea that may be bloody. If you notice these symptoms, stop taking cephalexin and contact your doctor as soon as possible.

Bacterial resistance: Misuse of an antibiotic such as cephalexin may lead to the growth of resistant bacteria that will not be killed by the antibiotic. If this happens, the antibiotic may not work for you in the future. Although you may begin to feel better when you first start taking cephalexin, you need to take all of the medication exactly as prescribed by your doctor to finish ridding your body of the infection and to prevent resistant bacteria from taking hold. Do not take cephalexin or other antibiotics to treat a viral infection such as the common cold; antibiotics do not kill viruses, and using them to treat viral infections can lead to the growth of resistant bacteria.

Kidney function: People with severe kidney problems may require a lower dose of cephalexin. People with kidney disease or reduced kidney function should discuss with their doctor how this medication may affect their medical condition, how their medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed.

Liver function: Cephalexin can cause a decrease in liver function, although this happens only occasionally. People with liver disease or reduced liver function should discuss with their doctor how this medication may affect their medical condition, how their medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed. If you experience signs of decreasing liver function, such as yellowing of the skin or whites of the eyes, dark urine, or pale stools, contact your doctor as soon as possible.

Overgrowth of organisms: Prolonged or repeated use of cephalexin may result in an overgrowth of bacteria or fungi and organisms that are not killed by the medication. This can cause other infections to develop, such as yeast infections.

Pregnancy: This medication should not be used during pregnancy unless the benefits outweigh the risks. If you become pregnant while taking this medication, contact your doctor immediately.

Breast-feeding: This medication passes into breast milk. If you are breast-feeding and taking cephalexin, it may affect your baby. Talk to your doctor about whether you should continue breast-feeding.

There may be an interaction between cephalexin and any of the following:

• aminoglycoside antibiotics (e.g., amikacin, gentamicin, tobramycin)
• BCG
• cholera vaccine
• furosemide
• metformin
• paromomycin
• probenecid
• sodium picosulfate
• typhoid vaccine
• warfarin

If you are taking any of these medications, speak with your doctor or pharmacist. Depending on your specific circumstances, your doctor may want you to:

• stop taking one of the medications,
• change one of the medications to another,
• change how you are taking one or both of the medications, or
• leave everything as is.

An interaction between two medications does not always mean that you must stop taking one of them. Speak to your doctor about how any drug interactions are being managed or should be managed.

Medications other than those listed above may interact with this medication. Tell your doctor or prescriber about all prescription, over-the-counter (non-prescription), and herbal medications you are taking. Also tell them about any supplements you take. Since caffeine, alcohol, the nicotine from cigarettes, or street drugs can affect the action of many medications, you should let your prescriber know if you use them.