What Cephalexin Is

Cephalexin is a beta-lactam antibiotic that belongs to the first-generation cephalosporins and is effective against gram-positive and some gram-negative bacteria. Its mechanism of action is the disruption of the bacterial cell wall. It works similarly to other substances within its class. Cephalexin is used to treat a range of bacterial infections, like those of the middle ear, skin, bone and joint, the urinary tract, strep throat, certain types of pneumonia, cellulitis. It can also prevent bacterial endocarditis. However, Cephalexin is ineffective against methicillin-resistant Staphylococcus aureus (MRSA), Pseudomonas, and Enterococcus. Cephalexin is a good alternative to penicillins in patients with mild or moderate penicillin intolerance. However, it is still not recommended for those with severe allergy to penicillins.

Recommendations for Use, Dosage and Overdose

Take cephalexin strictly as prescribed for your condition. Follow all orders of your physician and the directions on your prescription label. Do not change the dosage, dosing intervals or duration of the treatment on your own, without consulting your doctor! Do not use cephalexin for any other indications, other than the one it was prescribed for. If you take the drug in the form of oral suspension, shake the bottle before you measure a dose. Use a special dosing device (syringe, cup or spoon) if it is provided with the drug or ask your pharmacist for one if not. Do not use a regular kitchen spoon. Do not discontinue treatment ahead of time on your own, even if your symptoms improve. This puts you at a risk of further antibiotic-resistant infection. Note that cephalexin does not treat viral infections, such as flu or a common cold. Do not share cephalexin with other people even if they have similar symptoms as you have. This medication can distort the results of certain medical tests. Tell the diagnostician if you are using cephalexin. If you accidentally miss a dose, take it as soon as you remember. However, if it is almost time for your next scheduled dose, skip the missed one. Do not take extra dose to make up the missed one. If you overdose, seek emergency medical help at once or call the poison helpline.

Precautions and Contraindications

Cephalexin is not intended for patients who are allergic to it or similar cephalosporin antibiotics, like Cefzil, Ceftin, Omnicef, etc. Tell your physician about any known allergies, especially to penicillins or other antibiotics. The drug should also be taken with caution by patients with kidney or liver disease, stomach, intestinal or metabolic disorders such as diabetes, colitis, or malnourishment. To ensure that cephalexin is safe for you, tell your physician if you have:
  • Known allergy to any drugs (especially other antibiotics);
  • Liver or kidney disease;
  • History of intestinal conditions, such as colitis;
  • Intake of blood thinners.
Diabetic patients should take into account that liquid cephalexin suspention may contain sugar. Even though cephalexin is generally considered to be safe for pregnant and breastfeeding women, the data about the effect of the drug on the fetus and the newborn are still insufficient. If possible, restrain from cephalexin therapy during pregnancy. You might also need to temporarily discontinue breastfeeding while on cephalexin. In any case, inform your doctor if you are pregnant or breastfeeding.
Interactions with Other Drugs and Substances
Note that it might not be safe to use certain drugs and substances simultaneously with cephalexin. It may increase the side effects, blood cell levels, or make the drugs less effective. For example, probenecid delays the renal clearance of cephalexin  and other β-lactam antibiotics. Alcohol reduces the absorption rate of cephalexin and can also damage liver function. Cephalexin also interacts with an antidiabetic drug metformin, which can increase concentrations of metformin in the body. The effectiveness of cephalexin can also be reduced by histamine H2 receptor antagonists like ranitidine or cimetidine due to absorption delay and altered pharmacodynamics. As many other antibiotics, cephalexin can also interact with blood-thinners such as warfarin. Other drugs and substances, including prescription and over-the-counter medicines, vitamins, and herbal products, may also affect cephalexin. Inform your physician about any other medications or substances you are using.
Side Effects
The most common cephalexin side effects are gastrointestinal disturbances (nausea, vomiting, and diarrhea) and hypersensitivity (skin rashes, fever, urticaria, and anaphylaxis). Some studies report Clostridium difficile and Pseudomembranous colitis associated with cephalexin treatment. Signs of an allergic reaction may include rash, itching, peeling, blistering, swelling, troubled breathing. Get emergency medical help if you’ve noticed such symptoms. Consult your doctor as well, if you experience:
  • Severe stomach pain, watery or bloody diarrhea;
  • Jaundice;
  • Unusual easy bruising or bleeding (nose, mouth, vagina, or rectum), red or purple spots on your skin;
  • Insufficient urination;
  • Irritability, confusion, hallucinations; or
  • Severe skin or mucus membranes reactions – swollen lymph nodes, fever, sore throat, rash (especially if it is spreading), blistering and peeling on the skin, burning in your eyes.
Common cephalexin side effects that can fade away on their own most often include:
  • Diarrhea;
  • Dizziness, fatigue;
  • Headache, muscle or joint pain;
  • Vaginal discharge, dryness or itching.
However, you need to inform your doctor about any reactions you experience.
Keep in Mind
Before starting cephalexin treatment, inform your doctor fully and accurately about any conditions you have or have had in the past, any known allergies, drugs or substances you are taking and if you are pregnant or breastfeeding. This will help to reduce any severe reactions or side effects to the minimum. Take cephalexin only when prescribed and in strict accordance with doctor’s orders! Do not share it with other people, even if their symptoms are identical to yours. This may cause damage to their health. Remember that cephalexin, as well as other antibiotics, does not treat viral infections like flu or common cold! Do not prematurely discontinue the treatment; take the drug for the full prescribed course. Though the symptoms may improve sooner, the infection might not yet be eradicated. This increases your chances of developing antibiotic resistance. For the same reason, do not skip doses. Store cephalexin at room temperature away from moisture, heat, direct sunlight and out of children’s reach. The liquid suspension should be stored in the refrigerator. Throw away any unused liquid after 14 days. Dispose of any expired leftovers; do not take expired medication. Inform your doctor at once about any bad reactions to the drug or seek urgent medical help!