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, inform 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.
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 early in your course of treatment with cephalexin, you need to take the full course exactly as directed 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 a breast-feeding mother and are taking cephalexin, it may affect your baby. Talk to your doctor about whether you should continue breast-feeding.