Cephalexin (Keftab) vs. Common Antibiotic Alternatives: A Practical Comparison

Quick Summary

• Cephalexin (brand name Keftab) is a first‑generation cephalosporin best for skin, bone and urinary infections.
• Amoxicillin, dicloxacillin, clindamycin, azithromycin and trimethoprim‑sulfamethoxazole cover overlapping but distinct bacterial spectra.
• Choose based on infection type, allergy history, local resistance patterns and cost.
• All oral antibiotics share common side‑effects like GI upset; each class has unique cautions.
• Consult a pharmacist or physician before switching, especially if you have kidney issues or are pregnant.

When a doctor writes a prescription for a bacterial infection, the first question most patients ask is: "Is this the right drug for me?" In Canada, Cephalexin-sold under the brand name Keftab is a first‑generation cephalosporin antibiotic that targets gram‑positive bacteria and some gram‑negative strains. It’s a solid choice for many skin, bone and urinary infections, but it isn’t a one‑size‑fits‑all solution. This guide breaks down how Cephalexin stacks up against five widely used alternatives, helping you and your prescriber decide what fits your situation best.

What Is Keftab (Cephalexin)?

Cephalexin is a beta‑lactam antibiotic belonging to the cephalosporin class. It works by inhibiting bacterial cell‑wall synthesis, causing the microbe to burst under its own pressure. The drug is available in 250mg and 500mg oral tablets and a liquid suspension for children.

Typical adult dosage ranges from 250mg every 6hours for mild infections to 1g every 6hours for more serious cases. In patients with reduced kidney function, the dose must be adjusted to avoid accumulation.

How Cephalexin Works Compared to Other Classes

Cephalexin’s beta‑lactam ring is structurally similar to penicillins, giving it a comparable safety profile but a broader range against certain gram‑positive organisms like Staphylococcus aureus (non‑MRSA) and Streptococcus pyogenes. Unlike macrolides (e.g., azithromycin) that block protein synthesis, Cephalexin directly tears down the bacterial wall-making it less likely to cause drug‑interaction headaches with drugs metabolized by CYP enzymes.

When to Prefer Cephalexin Over Alternatives

Clinical guidelines (e.g., the Infectious Diseases Society of America) recommend Cephalexin for uncomplicated skin and soft‑tissue infections (SSTIs), uncomplicated urinary tract infections (UTIs) caused by susceptible strains, and osteomyelitis when the organism is known to be cefalosporin‑sensitive. If the patient has a documented penicillin allergy but tolerates cephalosporins, Cephalexin often remains safe because cross‑reactivity is below 5% for first‑generation agents.

Common Alternatives and Their Sweet Spots

Below is a quick snapshot of five antibiotics you’ll often hear mentioned alongside Cephalexin.

• Amoxicillin is a broad‑spectrum penicillin effective against many gram‑positive and some gram‑negative bacteria.
• Dicloxacillin is a penicillinase‑resistant penicillin used primarily for beta‑lactamase‑producing staphylococci.
• Clindamycin is a lincosamide that excels against anaerobes and MRSA‑susceptible strains.
• Azithromycin is a macrolide antibiotic prized for its long half‑life and good tissue penetration.
• Trimethoprim‑sulfamethoxazole (TMP‑SMX) is a sulfonamide combination effective against a range of urinary and respiratory pathogens.

Side‑Effect Profiles at a Glance

All oral antibiotics can cause nausea, diarrhea, and occasional rash. However, each class has signature concerns:

• Cephalexin: mild GI upset; rare allergic reactions; caution in renal impairment.
• Amoxicillin: higher rate of rash in patients with viral infections; possible hepatic enzyme elevation.
• Dicloxacillin: can lead to hepatic toxicity (especially with high doses) and neutropenia.
• Clindamycin: notorious for causing Clostridioides difficile colitis; watch for severe diarrhea.
• Azithromycin: QT‑prolongation risk; interacts with drugs metabolized by CYP3A4.
• TMP‑SMX: may trigger hyperkalemia, especially in patients on ACE inhibitors; avoid in pregnancy first trimester.

Comparison Table

Decision‑Making Checklist

Before you or your prescriber settle on a drug, run through this quick list:

1. Identify the pathogen (if known) and its susceptibility pattern.
2. Check for any drug allergies-especially penicillin or macrolide sensitivities.
3. Consider patient‑specific factors: kidney function, pregnancy status, age, and concurrent meds.
4. Review local resistance data (many health units publish annual antibiograms).
5. Factor in cost and insurance coverage-some drugs may be on formularies while others need prior approval.
6. Discuss dosing convenience; a once‑daily azithromycin may improve adherence compared to four‑times‑daily Cephalexin.

Cost and Accessibility in Canada (2025)

Generic Cephalexin tablets typically cost $0.40-$0.65 each at major Canadian pharmacies. Amoxicillin is a bit cheaper, while clindamycin and azithromycin sit at a higher price point, especially the branded versions. Many provincial drug plans cover Cephalexin and amoxicillin without extra co‑pay, but clindamycin often requires a special authorization. If you’re using an online pharmacy, compare the total price (including shipping) before ordering.

Safe Use Tips

• Finish the full course even if symptoms improve; stopping early fuels resistance.
• Take Cephalexin with a full glass of water; food can delay absorption but doesn’t reduce effectiveness.
• Stay hydrated to help kidneys flush out the drug, especially if you have reduced renal function.
• Report any severe rash, difficulty breathing, or persistent diarrhea to a health professional immediately.
• If you miss a dose, take it as soon as you remember unless it’s almost time for the next dose-don’t double up.

Frequently Asked Questions