Prescription Drug Information: Cephalexin (Page 3 of 3)
12 CLINICAL PHARMACOLOGY
12.1 Mechanism of Action
Cephalexin is a cephalosporin antibacterial drug [see Microbiology ( 12.4)].
12.3 Pharmacokinetics
Absorption: Cephalexin is acid stable and may be given without regard to meals. Following doses of 250 mg, 500 mg, and 1 g, average peak serum levels of approximately 9, 18, and 32 mcg/mL, respectively, were obtained at 1 hour. Serum levels were detectable 6 hours after administration (at a level of detection of 0.2 mcg/mL).
Distribution: Cephalexin is approximately 10% to 15% bound to plasma proteins.
Excretion: Cephalexin is excreted in the urine by glomerular filtration and tubular secretion. Studies showed that over 90% of the drug was excreted unchanged in the urine within 8 hours. During this period, peak urine concentrations following the 250 mg, 500 mg, and 1 g doses were approximately 1000, 2200, and 5000 mcg/mL respectively.
Drug Interactions
In healthy subjects given single 500 mg doses of cephalexin and metformin, plasma metformin mean Cmax and AUC increased by an average of 34% and 24%, respectively, and metformin mean renal clearance decreased by 14%. No information is available about the interaction of cephalexin and metformin following multiple doses of either drug.
12.4 Microbiology
Mechanism of Action
Cephalexin is a bactericidal agent that acts by the inhibition of bacterial cell-wall synthesis.
Resistance
Methicillin-resistant staphylococci and most isolates of enterococci are resistant to cephalexin. Cephalexin is not active against most isolates of Enterobacter spp., Morganella morganii , and Proteus vulgaris. Cephalexin has no activity against Pseudomonas spp., or Acinetobacter calcoaceticus. Penicillin-resistant Streptococcus pneumoniae is usually cross-resistant to beta-lactam antibacterial drugs.
Antimicrobial Activity
Cephalexin has been shown to be active against most isolates of the following bacteria both in vitro and in clinical infections [see Indications and Usage ( 1)].
Gram-positive bacteria
Staphylococcus aureus (methicillin-susceptible isolates only) Streptococcus pneumoniae (penicillin-susceptible isolates)
Gram-negative bacteria
Escherichia coli
Haemophilus influenzae
Klebsiella pneumoniae
Moraxella catarrhalis
Proteus mirabilis
Susceptibility Testing
For specific information regarding susceptibility test interpretive criteria and associated test methods and quality control standards recognized by FDA for this drug, please see: https://www.fda.gov/STIC.
13 NONCLINICAL TOXICOLOGY
13.1 Carcinogenesis, Mutagenesis, Impairment of Fertility
Lifetime studies in animals have not been performed to evaluate the carcinogenic potential of cephalexin. Tests to determine the mutagenic potential of cephalexin have not been performed. In male and female rats, fertility and reproductive performance were not affected by cephalexin oral doses up to 1.5 times the highest recommended human dose based upon body surface area.
16 HOW SUPPLIED/STORAGE AND HANDLING
Cephalexin Capsules USP
250 mg: Swedish orange body and gray cap imprinted “TEVA” on the cap and “3145” on the body, in bottles of 100 (NDC 0093-3145-01) and 500 (NDC 0093-3145-05).
500 mg: Swedish orange body and Swedish orange cap imprinted “TEVA” on the cap and “3147” on the body, in bottles of 100 (NDC 0093-3147-01) and 500 (NDC 0093-3147-05).
Store at 20° to 25°C (68° to 77°F) [See USP Controlled Room Temperature].
Dispense in a tight, light-resistant container.
Cephalexin for Oral Suspension* USP
(a cherry mixed fruit flavored formula)
125 mg/5 mL: bottles of 100 mL (NDC 0093-4175-73) and 200 mL (NDC 0093-4175-74).
250 mg/5 mL: bottles of 100 mL (NDC 0093-4177-73) and 200 mL (NDC 0093-4177-74).
Directions for mixing are included on the label.
Store dry powder at 20° to 25°C (68° to 77°F) [See USP Controlled Room Temperature].
Shake well before using. Keep tightly closed.
* After mixing, store in refrigerator. May be kept for 14 days without significant loss of potency.
17 PATIENT COUNSELING INFORMATION
Allergic Reactions
Advise patients that allergic reactions, including serious allergic reactions, could occur and that serious reactions require immediate treatment. Ask the patient about any previous hypersensitivity reactions to cephalexin, other beta-lactams (including cephalosporins) or other allergens (5.1)
Diarrhea
Advise patients that diarrhea is a common problem caused by antibacterial drugs and usually resolves when the drug is discontinued. Sometimes, frequent watery or bloody diarrhea may occur and may be a sign of a more serious intestinal infection. If severe watery or bloody diarrhea develops, advise patients to contact their healthcare provider.
Antibacterial Resistance
Counsel patients that antibacterial drugs including cephalexin capsules, and cephalexin for oral suspension, should only be used to treat bacterial infections. They do not treat viral infections (e.g., the common cold). When cephalexin capsules, and cephalexin for oral suspension are prescribed to treat a bacterial infection, tell patients that although it is common to feel better early in the course of therapy, the medication should be taken exactly as directed. Skipping doses or not completing the full course of therapy may (1) decrease the effectiveness of the immediate treatment and (2) increase the likelihood that bacteria will develop resistance and will not be treatable by cephalexin capsules, and cephalexin for oral suspension or other antibacterial drugs in the future.
Teva Pharmaceuticals USA, Inc.
North Wales, PA 19454
Rev. V 12/2020
Package/Label Display Panel
NDC 0093-3145-01
Cephalexin
Capsules USP
250 mg
Rx only
100 CAPSULES
Package/Label Display Panel
NDC 0093-3147-01
Cephalexin
Capsules USP
500 mg
Rx only
100 CAPSULES
Package/Label Display Panel
NDC 0093-4175-73
Cephalexin
for Oral Suspension, USP
125 mg per 5 mL
when reconstituted according to directions.
Usual Pediatric Dose: 25 to 50 mg per kg a day in four
divided doses. For more severe infections, dose may be
doubled. See accompanying literature.
Rx only
FOR ORAL USE ONLY
100 mL (when mixed)
Package/Label Display Panel
NDC 0093-4177-73
Cephalexin
for Oral Suspension, USP
250 mg per 5 mL
when reconstituted according to directions.
Usual Pediatric Dose: 25 to 50 mg per kg a day in four
divided doses. For more severe infections, dose may be
doubled. See accompanying literature.
Rx only
FOR ORAL USE ONLY
100 mL (when mixed)
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Labeler — Teva Pharmaceuticals USA, Inc. (001627975) |
Revised: 12/2020 Teva Pharmaceuticals USA, Inc.
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