Keflex

Kef·lex (kflks)

A trademark for the drug cephalexin.

---

Keflex,

trademark for an antibacterial (cephalexin).

---

cephalexin

Apo-Cephalex (CA), Biocef, Ceporex (UK), Keflex, Novo-Lexin (CA), Nu-Cephalex (CA), Panixine DisperDose, PMS-Cephalexin (CA)

Pharmacologic class: First-generation cephalosporin

Therapeutic class: Anti-infective

Pregnancy risk category B

Action

Interferes with bacterial cell-wall synthesis, causing cell to rupture and die. Active against many gram-positive bacteria; shows limited activity against gram-negative bacteria.

Availability

Capsules: 250 mg, 333 mg, 500 mg, 750 mg

Oral suspension: 100 mg/ml, 125 mg/5 ml, 250 mg/5 ml

Tablets: 250 mg, 500 mg

Tablets for oral suspension (DisperDose): 125 mg, 250 mg

⊘Indications and dosages

➣ Respiratory tract infections caused by streptococci; skin and skin-structure infections caused by methicillin-sensitive staphylococci and streptococci; bone infections caused by methicillin-sensitive staphylococci or Proteus mirabilis; genitourinary infections caused by Escherichia coli, P. mirabilis, and Klebsiella species; Haemophilus influenzae, methicillin-sensitive staphylococcal, streptococcal, and Moraxella catarrhalis infections

Adults: 1 to 4 g P.O. daily in divided doses (usually 250 mg P.O. q 6 hours). For uncomplicated cystitis, skin and soft-tissue infections, and streptococcal pharyngitis, 500 mg P.O. q 12 hours.

Children: 25 to 50 mg/kg/day P.O. in divided doses

➣ Otitis media caused by S. pneumoniae

Children: 75 to 100 mg/kg/day P.O. in four divided doses

Dosage adjustment

• Renal impairment

Contraindications

• Hypersensitivity to cephalosporins or penicillin

Precautions

Use cautiously in:
• renal impairment, phenylketonuria
• history of GI disease
• debilitated or emaciated patients
• elderly patients
• pregnant or breastfeeding patients.

Administration

• Give with or without food.
• Be aware that DisperDose tablet is intended for suspension. Mix with water before administering.
• Refrigerate oral suspension.

Route	Onset	Peak	Duration
P.O.	Rapid	1 hr	6-12 hr

Adverse reactions

CNS: fever, headache, lethargy, paresthesia, syncope, seizures

CV: edema, hypotension, vasodilation, palpitations, chest pain

EENT: hearing loss

GI: nausea, vomiting, diarrhea, abdominal cramps, oral candidiasis, pseudomembranous colitis

GU: vaginal candidiasis, nephrotoxicity

Hematologic: lymphocytosis, eosinophilia, bleeding tendency, hemolytic anemia, neutropenia, thrombocytopenia, agranulocytosis, bone marrow depression

Musculoskeletal: joint pain

Respiratory: dyspnea

Skin: rash, maculopapular and erythematous urticaria

Other: superinfection, chills, pain, allergic reaction, hypersensitivity reactions including anaphylaxis, serum sickness

Interactions

Drug-drug. Aminoglycosides, loop diuretics: increased risk of nephrotoxicity

Chloramphenicol: antagonistic effect

Probenecid: increased cephalexin blood level

Drug-diagnostic tests. Alanine aminotransferase, alkaline phosphatase, aspartate aminotransferase, bilirubin, blood urea nitrogen, creatinine, eosinophils, lactate dehydrogenase, lymphocytes: increased values

Coombs' test: false-positive result (especially in neonates whose mothers received drug before delivery)

Granulocytes, neutrophils, white blood cells: decreased counts

Patient monitoring

• Assess for signs and symptoms of serious adverse reactions, including hypersensitivity, severe diarrhea, and bleeding.
• During long-term therapy, monitor CBC and liver and kidney function test results.

Patient teaching

☞ Instruct patient to stop taking drug and contact prescriber immediately if he develops rash or difficulty breathing.
• Tell patient to take drug with full glass of water.
• Instruct patient to mix DisperDose tablet with water before taking.
• Advise patient to report severe diarrhea.
• As appropriate, review all other significant and life-threatening adverse reactions and interactions, especially those related to the drugs and tests mentioned above.