Compare Keflex vs. Penicillin

Head-to-head comparisons of medication uses, side effects, ratings, and more.

Keflex (cephalexin)

Prescription only
Treats bacterial infections.

Keflex (cephalexin) is good for treating many bacterial infections, and is available as a generic.

3.7/ 5 average rating with 686 reviewsforKeflex
Kills bacteria.

Penicillin Vk (Penicillin) is good for treating many bacterial infections and is available as a generic. You may need to use another form of birth control along with your birth control pills. It's also best taken on an empty stomach but it can cause an upset stomach.

3.9/ 5 average rating with 1297 reviewsforPenicillin
Upsides
  • Available in generic.
  • Available in different forms: tablet, capsule, and suspension.
  • Used to treat many types of bacterial infections.
  • Can be taken with or without food.
  • Generally few side effects compared with other antibiotics.
  • Available in generic.
  • Available in different forms: tablet, capsule and suspension.
  • Used to treat many types of bacterial infections.
Downsides
  • Can cause diarrhea.
  • You may need to take Keflex (cephalexin) 2 to 4 times a day, which can be hard to remember.
  • If you're allergic to penicillins or other antibiotics, you might not be able to take this medicine.
  • Many bacteria have developed resistance. Your doctor may run tests to see if Penicillin will work on your infection.
  • Can make birth control pills less effective.
  • Best taken on an empty stomach, but can cause stomach upset and diarrhea.
Used for
Dosage forms
  • Pill
  • Liquid
  • Pill
Price
No pricing information available
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Reviews
686 reviews so far
64%
saidit'sworth it
48%
saiditworked well
14%
saidit'sa big hassle

Have you used Keflex (cephalexin)?

Leave a review
1297 reviews so far
71%
saidit'sworth it
52%
saiditworked well
12%
saidit'sa big hassle

Have you used Penicillin Vk (Penicillin)?

Leave a review
Side effects
The Keflex (cephalexin) FDA package insert doesn’t have numbers about how common side effects are.
The Penicillin Vk (Penicillin) FDA package insert doesn’t have numbers about how common side effects are.
Risks and risk factors
  • Diarrhea
  • New infections while taking Keflex (cephalexin)
    • Weakened immune system
    • Not taking Keflex (cephalexin) correctly
  • Allergic reaction
    • History of penicillin or cephalosporin allergies
See more detailed risks and warnings
  • Diarrhea
  • Decreased effectiveness of birth control pills
  • Allergic reactions
    • Prior severe allergic reaction to Penicillin Vk (Penicillin)
See more detailed risks and warnings