Cephalexin (Keftab) vs Alternative Antibiotics: Comparison Guide

Every year the NHS records over three million courses of Cephalexin a first‑generation cephalosporin sold under the brand name Keftab. It’s a go‑to for skin and soft‑tissue infections, but patients often wonder whether another pill might work better, cost less, or be safer in pregnancy. This guide breaks down the science, the side‑effects, and the price tags so you can see where Cephalexin stands next to its most common rivals.

Cephalexin is the keyword that’ll keep popping up, because it’s the centerpiece of this comparison.

Key Takeaways

• Cephalexin is a first‑generation cephalosporin, ideal for uncomplicated skin infections.
• Amoxicillin covers many of the same bugs but adds activity against some Gram‑negative bacteria.
• Doxycycline offers a broad spectrum and works well for atypical respiratory bugs.
• Clindamycin is useful for anaerobic infections and MRSA, but carries a higher risk of C.difficile.
• Cefuroxime bridges the gap between first‑ and second‑generation cephalosporins, with a broader Gram‑negative reach.

What Is Cephalexin (Keftab)?

Cephalexin belongs to the cephalosporin class - a family of beta‑lactam antibiotics that interfere with bacterial cell‑wall synthesis. Its chemical formula is C₁₆H₁₈N₃O₄S, and it’s marketed in the UK primarily as the 250mg and 500mg oral tablets. The drug is absorbed quickly, reaching peak plasma concentrations within an hour, and is excreted unchanged by the kidneys.

Typical uses include:

• Uncomplicated cellulitis
• Impetigo
• Simple urinary tract infections (UTIs) caused by susceptible E.coli
• Bone and joint infections where the pathogen is known to be sensitive

Because it’s a beta‑lactam, Cephalexin works best against Gram‑positive cocci such as Staphylococcus aureus (non‑MRSA) and Streptococcus pyogenes.

Dosing, Side Effects, and Safety Profile

Standard adult dosing is 250mg every six hours or 500mg every 12hours for 7‑10days, depending on infection severity. For kids, the dose is weight‑based (25mg/kg/day divided three times).

Common side effects (seen in up to 10% of patients) include mild nausea, diarrhoea, and a transient rash. Rare but serious reactions involve Stevens‑Johnson syndrome and anaphylaxis, especially in patients with a penicillin allergy - cross‑reactivity is reported at about 5%.

Renal impairment requires dose adjustment, and the drug is generally considered safe in pregnancy (Category B in the UK) though doctors prefer erythromycin for certain infections.

Top Alternatives to Cephalexin

Below are the most frequently prescribed oral antibiotics that can be swapped for Cephalexin, each with its own niche.

Amoxicillin a broad‑spectrum penicillin often used for respiratory and ear infections

Amoxicillin’s spectrum covers many Gram‑positive bacteria plus a larger share of Gram‑negative organisms like H.influenzae. It’s taken three times daily, usually 500mg, and is cheap on the NHS formulary.

Doxycycline a tetracycline antibiotic effective against atypical pathogens and some resistant strains

Doxycycline is a favorite for Lyme disease, chlamydia, and community‑acquired pneumonia caused by Mycoplasma. The usual adult dose is 100mg twice daily. It’s not recommended for pregnant women or children under eight because it can affect tooth development.

Clindamycin a lincosamide that excels against anaerobes and certain MRSA strains

Clindamycin is often reserved for deep skin infections where anaerobes are suspected. It’s dosed 150‑300mg four times daily. The biggest downside is a 15‑20% chance of causing Clostridioides difficile colitis.

Cefuroxime a second‑generation cephalosporin with better Gram‑negative coverage than Cephalexin

Cefuroxime bridges the gap between first‑ and later‑generation cephalosporins. It’s taken twice daily (250‑500mg) and handles infections like otitis media and sinusitis more reliably than Cephalexin.

Side‑by‑Side Comparison

Which One Fits Your Situation?

Skin infections without MRSA suspicion? Cephalexin remains the cheapest, well‑tolerated first line.

Lower respiratory tract infections? Amoxicillin or Cefuroxime usually beat Cephalexin because they hit more Gram‑negative bacteria.

Travel‑related fevers, atypical pneumonia, or chlamydia? Doxycycline’s broad coverage and excellent tissue penetration make it the obvious pick.

Deep abscesses, diabetic foot infections, or proven MRSA? Clindamycin shines despite its CDI risk, especially if you need an oral option after IV therapy.

Always factor in allergy history - a penicillin‑allergic patient may tolerate Cephalexin better than amoxicillin, but cross‑reactivity must be checked.

Talking to Your Doctor

When you’re not sure which antibiotic suits you, bring these points to the consultation:

1. Describe the infection (location, severity, recent travel).
2. Mention any known drug allergies.
3. Ask about pregnancy or breastfeeding considerations.
4. Inquire about the shortest effective course - many guidelines now favour 5‑day regimens for uncomplicated skin infections.
5. Request clarification on side‑effects you’re most worried about, like diarrhoea or photosensitivity.

Most GPs will follow NICE guidelines, which currently list Cephalexin as first‑line for uncomplicated cellulitis, but they’ll switch to alternatives if culture results or risk factors dictate.

Frequently Asked Questions

Can I take Cephalexin if I’m allergic to penicillin?

Cross‑reactivity is low (about 5%), but you should alert your doctor. If you’ve had a severe reaction, they may opt for a non‑beta‑lactam like doxycycline.

Is Cephalexin safe during pregnancy?

Yes, it’s classified as Category B in the UK, meaning animal studies haven’t shown risk and there’s no evidence of harm in humans. Still, the doctor will weigh benefits against any alternatives.

Why does my doctor sometimes prescribe amoxicillin instead of Cephalexin?

Amoxicillin covers a broader range of Gram‑negative bacteria, making it a better fit for ear, sinus, or mild chest infections. Cephalexin is narrower and cheaper, so it’s chosen when the bug is likely a Gram‑positive skin pathogen.

How long should I stay on Cephalexin?

Typical courses run 7‑10days for skin infections, but recent NICE updates allow 5‑day regimens if symptoms improve quickly. Always finish the prescribed course unless your doctor says otherwise.

What should I do if I develop diarrhoea while on an antibiotic?

Mild diarrhoea is common; stay hydrated and monitor severity. If you see watery stools with abdominal cramping, blood, or fever, contact your GP - it could be C.difficile, especially with clindamycin.