Cephalexin: Uses, Doses, Side Effects & Interactions

Cephalexin is an antibiotic that is used to treat a variety of infections throughout the body. Allergic reactions to Cephalexin are common.

Cephalexin can be used to treat a variety of infections throughout the body. It should be noted that this drug cannot combat illnesses such as colds or the flu that are caused by viral infections. These are very similar to function of penicillin, which is used to kill off bacteria that are causing an infection throughout the body. These drugs have a strict expiration date which must be adhered to in order to ensure that the medication will work properly. This, along with any other instructions you will need, is printed on the prescription packaging. Your doctor can assist you with any further direction that may be necessary.

Indications and Usage

Cephalexin is the main ingredient used in GenRx Cepalexin. You may also receive this medication under the brand names Keflex or Pulvules. These drugs come in capsule, tablet or liquid form, all of which are taken by mouth roughly every 6 or 12 hours. Cephalexin should be taken with food in order to avoid upset stomach. Capsule forms should be taken with a full glass of water. In order to ensure the medication's effectiveness, you should continue taking cephalexin for 7-10 days or until your doctor informs you that your prescription has finished.

Cephalexin may be used to treat respiratory tract infections including those in the chest, tonsils, throat or lungs. You may also be prescribed this drug to assist in curing infections of the skin, ears, sinuses or genitourinary tract, which included the bladder, prostate and kidneys. If you tend to react poorly to similar antibiotics such as penicillin, you should not take cephalexin. Inform your doctor about any medical allergies you are aware of before starting your prescription to help avoid a serious reaction.

Cephalexin Dosage

The recommended dosing for adults is one 250 mg capsule taken every 6 hours. This may be adjusted depending on the condition of your infection or your size. In some cases this may be increased to 500 mg every 12 hours. If you forget to take a dose, take it as soon as you remember, but not if it is close to the next time you should be taking a dose. You should not double up doses to make up for those you have missed.

Doses should not exceed 4 grams per day, or 100 mg in children. The minimum effective dose for adults is 333 mg per day, while that for a child is 25 mg per day. Children are typically given between 25 and 50 mg per day in divided doses. In cases of extreme infection, dosage of 75 to 100 mg may be administered under direct medical supervision. The size and strength of your child's prescription will be based on their size and weight. Cephalexin should not be given to children under a year old.

Those who suffer from kidney disease should have their condition carefully monitored while on cephalexin. When the patient is administered high doses, they may not be excreted properly, which could lead to toxic reactions to the medication. Those with decreased renal function are advised to be especially cautious with their dosing size.

Elderly patients may also require a lower dose as they are more likely to develop decreased renal function while using cephalexin. Patients may be asked to monitor their renal function while on the drug so their dosing can be adjusted should any adverse reactions appear.

Cephalexin Side Effects

Common side effects to cephalexin include upset stomach, diarrhea and vomiting. These symptoms can often be avoided if the patient takes their dose with food or milk. If these symptoms persist, become worse or are severe, you should inform your doctor. They will inform you as to whether or not it is appropriate to continue taking your medication. Do not stop taking cephalexin unless you have gotten advice from a medical professional.

Because of the bacterial content of cephalexin, you may develop vaginal thrush, oral thrush, headaches, or aching swollen joints. In most patients, these conditions are mild and go away within a few doses of the medication. If the condition appears to be severe or is interrupting your ability to function, then inform your doctor to determine the best course of action.

Allergic reactions to cephalexin are quite common, especially in those who have allergies to similar antibiotics. If you begin to develop itching, severe skin rash, hives, difficulty breathing or swallowing, wheezing, or mouth sores while you are on cephalexin, then contact medical assistance right away. You should also contact your local poison control center to determine the best course of action. If at any time it appears as though your reaction is severe or may cause you to stop breathing. then it is essential that you contact emergency medical services as soon as possible.

In less common cases, patients have reported yellowing of the skin or eyes, dark stools, bleeding or bruising that is unexplained, chills, fever, agitation or confusion which includes hallucinations. These are signs of a serious reaction and should be given medical attention immediately. Contact your doctor if any of these signs begin to appear or if you begin showing other symptoms of jaundice. They will advise you as to the best course of action.

Pregnant women are not directly at risk for developing side effects to cephalexin, but they are advised to take caution while taking this medication. Studies have not shown any harm to the fetus, but pregnant women and those who are breast feeding will transfer the drug to their child, which could lead to an allergic reaction or immune response. Talk to your doctor about these risks to determine if it is safe to start a cephalexin prescription.

Seniors and those with kidney disease are advised to watch their condition carefully while on cephalexin. High doses have been linked to an increased risk of toxic reactions, decreased renal function as well as increased sensitivity to more common side effects. Though no studies have yet been done, children are advised to be monitored for similar conditions. You will also need to watch children more closely for signs of an allergic reaction as their medical history may not have this information yet.


Due to the chemical makeup of cephalexin, you should not take blood thinners, including warfarin, while you are on this drug. You may also need to avoid drugs that contain metformin including Glucophage, Riomet, Actoplus, Benemid, or Avandament. These could interact with your cephalexin prescription and cause a dangerous reaction. If you are on any of these drugs and have developed a case of diarrhea, then inform your doctor immediately. This is especially important if your diarrhea is watery or appears to have blood in it.



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