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To reduce the development of drug-resistant bacteria and maintain the effectiveness of Keflex and other antibacterial drugs, Keflex should be used only to treat or prevent infections that are proven or strongly suspected to be caused by bacteria.
Keflex® Capsules (Cephalexin Capsules, USP) is a semisynthetic cephalosporin antibiotic intended for oral administration. It is 7-(D-α-Amino-α-phenylacetamido)-3-methyl-3-cephem-4-carboxylic acid monohydrate. Cephalexin has the molecular formula C16H17N3O4S•H2O and the molecular weight is 365.41.
Cephalexin has the following structural formula:
The nucleus of cephalexin is related to that of other cephalosporin antibiotics. The compound is a zwitterion; i.e., the molecule contains both a basic and an acidic group. The isoelectric point of cephalexin in water is approximately 4.5 to 5. The crystalline form of cephalexin which is available is a monohydrate. It is a white to cream colored crystalline solid having a bitter taste. Solubility in water is low at room temperature; 1 or 2 mg/mL may be dissolved readily, but higher concentrations are obtained with increasing difficulty.
The cephalosporins differ from penicillins in the structure of the bicyclic ring system. Cephalexin has a D-phenylglycyl group as substituent at the 7-amino position and an unsubstituted methyl group at the 3-position.
Each capsule contains cephalexin monohydrate equivalent to 250 mg, 500 mg or 750 mg of cephalexin. The capsules also contain cellulose, D & C Yellow No. 10, F D & C Blue No. 1, F D & C Yellow No. 6, gelatin, magnesium stearate, silicone, titanium dioxide, and other inactive ingredients.
What are the possible side effects of cephalexin (Keflex, Panixine)?
Get emergency medical help if you have any of these signs of an allergic reaction: hives; difficulty breathing; swelling of your face, lips, tongue, or throat.
Call your doctor at once if you have any of these serious side effects:
- diarrhea that is watery or bloody;
- seizure (convulsions);
- fever, sore throat, and headache with a severe blistering, peeling, and red skin rash;
- pale or yellowed skin, dark colored urine, fever, confusion or weakness;
- easy bruising or bleeding, unusual weakness;
- confusion, agitation,...
What are the precautions when taking cephalexin (Keflex)?
Before taking cephalexin, tell your doctor or pharmacist if you are allergic to it; or to penicillins or other cephalosporins (such as cefpodoxime); or if you have any other allergies. This product may contain inactive ingredients, which can cause allergic reactions or other problems. Talk to your pharmacist for more details.
Before using this medication, tell your doctor or pharmacist your medical history, especially of: kidney disease, stomach/intestinal disease (such as colitis).
The liquid form of this product may contain sugar. Caution is advised if you have diabetes. Ask your doctor or pharmacist about using this product safely.
Before having surgery, tell your doctor or dentist about all the products you use (including prescription drugs, nonprescription...
Last reviewed on RxList: 2/27/2015
This monograph has been modified to include the generic and brand name in many instances.
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