What is the recommended dosage of Keflex (Cephalexin) for pregnant women?

Keflex (Cephalexin) Dosing in Pregnancy

The standard dosage of Keflex (cephalexin) during pregnancy is 250-500 mg orally every 6 hours, with a maximum daily dose of 4 grams. This dosing regimen is effective for treating common infections during pregnancy while maintaining an appropriate safety profile.

Safety Profile in Pregnancy

Cephalexin is considered safe for use during all trimesters of pregnancy. It belongs to the class of first-generation cephalosporins, which have established safety records in pregnant women. The medication:

• Reaches high bactericidal concentrations in the urinary tract
• Does not disturb lower bowel flora due to absorption high in the intestinal tract
• Has minimal protein binding
• Is rapidly cleared by the kidneys with 70-100% of the dose found in urine within 6-8 hours 1

Common Indications During Pregnancy

Cephalexin is particularly effective for:

• Urinary tract infections (UTIs)
• Upper and lower respiratory tract infections
• Skin and soft tissue infections

Specific Dosing Recommendations

1. Standard treatment dosing:

   • 250-500 mg orally every 6 hours
   • Duration typically 7-10 days depending on infection type

2. UTI prophylaxis dosing:

   • 250 mg as a single dose post-coital prophylaxis for women with history of recurrent UTIs 2, 3
   • This prophylactic approach has shown significant effectiveness in preventing recurrent UTIs during pregnancy

3. Dosage adjustments:

   • For patients with renal impairment (creatinine clearance <30 mL/min), dose reduction proportional to decreased function is required 1

Clinical Evidence

Research has demonstrated that cephalexin is effective in treating bacteriuria during pregnancy, with bacteriological cure rates of approximately 74% at 2 weeks and 60% at 6 weeks 4. No significant toxicity to the fetus has been observed that could be attributed to cephalexin.

Practical Considerations

• Cephalexin can be administered in relatively high oral doses without gastrointestinal irritation
• Due to its stability and chemical configuration, it causes a very low incidence of allergic reactions
• It is not absorbed from the stomach but is totally and rapidly absorbed in the upper intestine
• Concentrations of 500-1000 μg/mL of urine follow 250-500 mg oral doses, which is many times greater than the minimum inhibitory concentration for common urinary tract pathogens 1

Monitoring During Treatment

• Monitor for signs of allergic reaction, particularly in patients with known penicillin allergy (though cross-reactivity is relatively low)
• For prolonged therapy, periodic assessment of renal and hepatic function is recommended
• Follow-up urine cultures may be warranted to confirm resolution of infection in cases of UTI

Cephalexin remains a valuable antibiotic for pregnant women due to its proven safety profile, effectiveness against common pathogens, and favorable pharmacokinetic properties that allow for high urinary concentrations with minimal systemic effects.