Compare Keflex vs. Penicillin

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

Keflex
(Cephalexin)

Penicillin Vk
(Penicillin)

Kills bacteria. Keflex (Cephalexin) is good for treating many bacterial infections and is available as generic. However, if you are on medications to thin your blood, you can be more likely to bleed.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.
Find lowest prices
Powered by GoodRxSave on your next prescription. Be sure you’re getting the lowest price for your medication, even if you have insurance.
No pricing data for this drug at this filter setting. Try searching onGoodRx
Reviews & ratings
Button Group. All currently active
Button Group. All currently active
5.0662739322533135Keflex
Reviews for Keflex (Cephalexin)
63%
of people say Keflex (Cephalexin) is worth it
48%
say it works well
14%
say it's a big hassle
Reviews for Penicillin Vk (Penicillin)
71%
+8% vs. Keflex (Cephalexin)
52%
+4% vs. Keflex (Cephalexin)
12%
+2% vs. Keflex (Cephalexin)
Side effects
KeflexPenicillin

The Keflex FDA package insert doesn’t have numbers about how common side effects are.

More about Keflex side effects »

The Penicillin FDA package insert doesn’t have numbers about how common side effects are.

More about Penicillin side effects »
How it works
KeflexPenicillin
Keflex (Cephalexin) is an antibiotic. It kills bacteria by preventing them from making their own protective covering.Penicillin Vk (Penicillin) is an antibiotic. It kills bacteria by preventing them from making their own protective covering.
Type of medication
KeflexPenicillin
Antibiotic
Cephalosporin
Prescription only
Antibiotic
Penicillin
Prescription only
Available as
KeflexPenicillin
  • Pill
  • Powder for oral suspension
  • Pill
Used for (click to learn more)
KeflexPenicillin
Risk factors for serious side effects
KeflexPenicillin
    Detailed Keflex (Cephalexin) risks & warnings »
        • Prior severe allergic reaction to Penicillin Vk (Penicillin)
        Detailed Penicillin Vk (Penicillin) risks & warnings »
        Pregnancy category
        KeflexPenicillin
        BFDA pregnancy category (Probably safe)

        Research studies with animals haven’t found a risk to unborn babies, but it hasn’t been properly studied in humans.

        See the FDA package insert
        NFDA pregnancy category (Unknown)

        The FDA hasn’t classified this medicine’s effects on unborn babies. Talk with your doctor about this medicine if you’re pregnant or planning on it.

        See the FDA package insert
        Alcohol
        No specific alcohol-related info.No specific alcohol-related info.
        Food
        • Can be taken with or without food.
        • Try to take it on an empty stomach. If this gives you an upset stomach, take it with food.
        Kidneys and liver
        No specific kidneys and liver-related info.No specific kidneys and liver-related info.
        Sex
        No specific sex-related info.No specific sex-related info.
        Sleep
        No specific sleep-related info.No specific sleep-related info.
        Weight
        No specific weight-related info.No specific weight-related info.
        Upsides and benefits
        KeflexPenicillin
        • Available in different forms: tablet, capsule, and suspension.
        • Less resistance seen in bacteria to this antibiotic. Your doctor may run tests to see which antibiotics will kill the bacteria causing your infection.
        • Can be taken with or without food.
        • Available in generic.
        • Used to treat many types of bacterial infections.
        • Available in different forms: tablet, capsule and suspension.
        • Available in generic.
        • Used to treat many types of bacterial infections.
        Downsides and risks
        KeflexPenicillin
        • If you're on blood thinners (anticoagulants), talk to your doctor, it may make you more likely to bleed.
        • If you have to take any live vaccines, talk to your doctor. You may have to postpone it.
        • Can cause diarrhea.
        • 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.
        Tips from our pharmacists for people taking the medication
        KeflexPenicillin
        • Take this medication exactly as your doctor tells you to.
        • Store the suspension in the refrigerator. All other forms can be kept at room temperature.
        • Space out vitamins by a couple hours if you're taking this medication.
        • Take this medication exactly how your doctor tells you to.
        • If you're taking birth control pills, this medication can make them less effective.
        • Try to take it on an empty stomach. If this gives you an upset stomach, take it with food.
        • Can cause diarrhea, nausea or vomiting.
        Learn more
        More about KeflexSide effectsReviews & ratingsAlternativesFDA package insert
        More about PenicillinSide effectsReviews & ratingsAlternativesFDA package insert