Formulary
Cefalexin: Indications, Dosing, Side Effects and Interactions
Cephalosporins are antibacterials that attach to penicillin binding proteins to interrupt cell wall biosynthesis, leading to bacterial cell lysis and death.
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Cefalexin: Indications, Dosing, Side Effects and Interactions
Cephalosporins are antibacterials that attach to penicillin binding proteins to interrupt cell wall biosynthesis, leading to bacterial cell lysis and death.
Drug action
Cephalosporins are antibacterials that attach to penicillin binding proteins to interrupt cell wall biosynthesis, leading to bacterial cell lysis and death.
Indications and dose
**Susceptible infections due to sensitive Gram-positive and Gram-negative bacteria**
- **Child** (By Mouth): 12-17 years 500 mg 2-3 times a day.
- **Adult** (By Mouth): 250 mg every 6 hours, alternatively 500 mg every 8-12 hours; increased to 1-1.5 g every 6-8 hours, increased dose used in severe infections.
**Serious susceptible infections due to sensitive Gram-positive and Gram-negative bacteria**
- **Child** (By Mouth): 12-17 years 1-1.5 g 3-4 times a day.
**Hospital-acquired pneumonia,Acute diverticulitis [in combination with metronidazole]**
- **Adult** (By Mouth): 500 mg 2-3 times a day for 5 days then review, alternatively 1-1.5 g 3-4 times a day for 5 days then review, increased dose used in severe infection.
**Prophylaxis of recurrent urinary-tract infection in non-pregnant females [using single-dose antibacterial prophylaxis]**
- **Child** (By Mouth): 16-17 years 500 mg for 1 dose, dose to be taken following exposure to a trigger.
- **Adult** (By Mouth): 500 mg for 1 dose, dose to be taken following exposure to a trigger.
**Prophylaxis of recurrent urinary-tract infection [using daily antibacterial prophylaxis]**
- **Child** (By Mouth): 16-17 years 125 mg once daily, dose to be taken at night, seek specialist advice if considering use for prophylaxis during pregnancy, in male patients, or for recurrent upper urinary-tract infection or recurrent complicated lower urinary-tract infection.
- **Adult** (By Mouth): 125 mg once daily, dose to be taken at night, seek specialist advice if considering use for prophylaxis during pregnancy, in male patients, or for recurrent upper urinary-tract infection or recurrent complicated lower urinary-tract infection.
**Prophylaxis of recurrent urinary-tract infection [using daily antibacterial prophylaxis] (initiated under specialist supervision)**
- **Child** (By Mouth): 3 months-15 years 12.5 mg/kg once daily (max. per dose 125 mg), dose to be taken at night.
**Acute pyelonephritis,Urinary-tract infection (catheter-associated)**
- **Child** (By Mouth): 12-17 years 500 mg 2-3 times a day for 7 to 10 days, alternatively 1-1.5 g 3-4 times a day for 7 to 10 days, increased dose used in severe infections.
- **Adult** (By Mouth): 500 mg 2-3 times a day for 7 to 10 days, alternatively 1-1.5 g 3-4 times a day for 7 to 10 days, increased dose used in severe infections.
**Lower urinary-tract infection in pregnancy**
- **Child** (By Mouth): 12-17 years 500 mg twice daily for 7 days.
- **Adult** (By Mouth): 500 mg twice daily for 7 days.
**Lower urinary-tract infection**
- **Child** (By Mouth): 12-15 years 500 mg twice daily for 3 days.
**Susceptible infections due to sensitive Gram-positive and Gram-negative bacteria for cefalexin**
- **Neonate up to 7 days** (By mouth): 25 mg/kg twice daily (max. per dose 125 mg).
- **Neonate 7 days to 20 days** (By mouth): 25 mg/kg 3 times a day (max. per dose 125 mg).
- **Neonate 21 days to 28 days** (By mouth): 25 mg/kg 4 times a day (max. per dose 125 mg).
- **Child 1-11 months** (By mouth): 12.5 mg/kg twice daily, alternatively 125 mg twice daily.
- **Child 1-4 years** (By mouth): 12.5 mg/kg twice daily, alternatively 125 mg 3 times a day.
- **Child 5-11 years** (By mouth): 12.5 mg/kg twice daily, alternatively 250 mg 3 times a day.
- **Child 12-17 years** (By mouth): 500 mg 2-3 times a day.
**Serious susceptible infections due to sensitive Gram-positive and Gram-negative bacteria for cefalexin**
- **Child 1 month-11 years** (By mouth): 25 mg/kg 2-4 times a day (max. per dose 1 g).
- **Child 12-17 years** (By mouth): 1-1.5 g 3-4 times a day.
**Prophylaxis of recurrent urinary-tract infection in non-pregnant females [using single-dose antibacterial prophylaxis] for cefalexin**
- **Child 16-17 years** (By mouth): 500 mg for 1 dose, dose to be taken following exposure to a trigger.
**Prophylaxis of recurrent urinary-tract infection [using daily antibacterial prophylaxis] for cefalexin**
- **Child 16-17 years** (By mouth): 125 mg once daily, dose to be taken at night, seek specialist advice if considering use for prophylaxis during pregnancy, in male patients, or for recurrent upper urinary-tract infection or recurrent complicated lower urinary-tract infection.
**Prophylaxis of recurrent urinary-tract infection [using daily antibacterial prophylaxis] (initiated under specialist supervision) for cefalexin**
- **Child 3 months-15 years** (By mouth): 12.5 mg/kg once daily (max. per dose 125 mg), dose to be taken at night.
**Acute pyelonephritis, Urinary-tract infection (catheter-associated) for cefalexin**
- **Child 3-11 months** (By mouth): 125 mg twice daily for 7 to 10 days, alternatively 12.5 mg/kg twice daily for 7 to 10 days, alternatively 25 mg/kg 2-4 times a day (max. per dose 1 g) for 7 to 10 days, increased dose used in severe infections.
- **Child 1-4 years** (By mouth): 125 mg 3 times a day for 7 to 10 days, alternatively 12.5 mg/kg twice daily for 7 to 10 days, alternatively 25 mg/kg 2-4 times a day (max. per dose 1 g) for 7 to 10 days, increased dose used in severe infections.
- **Child 5-11 years** (By mouth): 250 mg 3 times a day for 7 to 10 days, alternatively 12.5 mg/kg twice daily for 7 to 10 days, alternatively 25 mg/kg 2-4 times a day (max. per dose 1 g) for 7 to 10 days, increased dose used in severe infections.
- **Child 12-17 years** (By mouth): 500 mg 2-3 times a day for 7 to 10 days, alternatively 1-1.5 g 3-4 times a day for 7 to 10 days, increased dose used in severe infections.
**Lower urinary-tract infection in pregnancy for cefalexin**
- **Child 12-17 years** (By mouth): 500 mg twice daily for 7 days.
**Lower urinary-tract infection for cefalexin**
- **Child 3-11 months** (By mouth): 12.5 mg/kg twice daily for 3 days, alternatively 125 mg twice daily for 3 days.
- **Child 1-4 years** (By mouth): 12.5 mg/kg twice daily for 3 days, alternatively 125 mg 3 times a day for 3 days.
- **Child 5-11 years** (By mouth): 12.5 mg/kg twice daily for 3 days, alternatively 250 mg 3 times a day for 3 days.
- **Child 12-15 years** (By mouth): 500 mg twice daily for 3 days.
Side effects
Common or very common Abdominal pain; diarrhoea; dizziness; eosinophilia; headache; leucopenia; nausea; neutropenia; pseudomembranous enterocolitis; skin reactions; thrombocytopenia; vomiting Uncommon Anaphylactic reaction; angioedema Rare or very rare Agranulocytosis; haemolytic anaemia; nephritis tubulointerstitial (reversible); severe cutaneous adverse reactions (SCARs) Side-effects For cefalexin Frequency not known Agitation; arthritis; confusion; fatigue; gastrointestinal discomfort; genital pruritus; hallucination; hepatitis (transient); hypersensitivity; increased risk of infection; jaundice cholestatic (transient); joint disorders; vaginal discharge
Interactions
**Severe interactions:**
- A potential interaction between cefalexin and metformin may result in an accumulation of metformin and could result in fatal lactic acidosis.
**Other interactions (5):**
- As cephalosporins like cefalexin are only active against proliferating microorganisms, they should not be combined with bacteriostatic antibiotics.
- As a result, cefalexin plasma levels are increased and sustained for longer periods.
- If associated with highly potent diuretics (ethacrynic acid, furosemide) or other potentially nephrotoxic antibiotics (aminoglycosides, polymyxin, colistin), cephalosprins may show higher...
- Combined use of cephalosporins and oral anticoagulants may prolong prothrombin time.
- Hypokalaemia has been described in patient taking cytotoxic drugs for leukaemia when they were given gentamicin and cefalexin.
Pregnancy
Lower urinary-tract infection in pregnancy for cefalexin By mouth Child 12-17 years 500 mg twice daily for 7 days. Adult 500 mg twice daily for 7 days.
Breast feeding
Present in milk in low concentration, but appropriate to use.
Renal impairment
Dose adjustments In adults: Max. 3 g daily if eGFR 40-50 mL/minute/1.73 m 2 . Max. 1.5 g daily if eGFR 10-40 mL/minute/1.73 m 2 . Max. 750 mg daily if eGFR less than 10 mL/minute/1.73 m 2 . In children: Reduce dose in moderate impairment.
Medicinal forms
Tablet,Capsule,Suspension
Clinical governance
**Author:** MedNext Clinical Team. **Clinical reviewer:** Dr Shameer Deen, MBBS, MS, MRCS. **Sources:** BNF, Indian Pharmacopoeia, CIMS India. **Correction:** Report errors at support@mednext.academy.
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