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Doctor insights on: I'm Allergic To Penicillin Can I Take Cephalexin 500mg

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I'm allergic to penicillin, can I take keflex?

I'm allergic to penicillin, can I take keflex?

Maybe: Penicillins (like amoxil) & cephalosporins (like keflex) are both beta-lactam antibiotics named because of their ringed chemical structure. Allergy to penicillins is sometimes directed against this ring, and an allergic reaction may also occur if a similar antibiotic is taken. It is estimated that about 10% of penicillin-allergic patients are also allergic to cephalosporins like keflex. ...Read more

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Dr. Aaron Milstone
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Dr. James Dukelow
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Keftabs (Definition)

Keftabs is a first generation cephalosporin which is a kind of cephalosporin type drug (anti-bacterial ...Read more


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Allergic to penicillin can I take keflex?

Likely, not certain: The majority of people who are told they are allergic to penicillin are not actually so (they get rashes for other reasons, e.g.). Of those that are allergic, about 70% or more will lose the allergy after about 10 years. If you are still allergic, there is about a 10% chance of cross-reaction to 1st-gen cephalosporins like keflex. An allergist can perform testing to judge your risk for a reaction. ...Read more

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Dr. Aaron Milstone
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If i'm allergic to penicillin is it safe to take keflex pulvales?

No: If you are truly allergic to penicillin, you should avoid all penicillin derivatives and the first generation cephalosporins. Keflex is a first gen. Cephalosporin and may cross react with penicillin. See a board certified allergist to help you determine if penicillin is a true allergy for you. ...Read more

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I m allergic to penicillin keflex azithromiacin my daughter has scarlet fever and i m worried about what i can take if i get it ?

I m allergic to penicillin keflex azithromiacin my daughter has scarlet fever and i m worried about what i can take if i get it ?

Don't panic: Scarlet fever is an acute febrile illness, primarily affecting children, caused by group a beta-hemolytic streptococci. Clinical manifestations include fever, sore throat, and fine sand-paper like rash caused by a toxin produced by the strep. Although penicillins are antibiotics of choice, there are other antibiotics that are effective. Your doctor will know. A throat culture is helpful. ...Read more

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What to do if I have strept throat, and im allergic to penicillin, can take amoxicillin or keflex instead?

What to do if I have strept throat, and im allergic to penicillin, can take amoxicillin or keflex instead?

No : Amoxicillin is within penicillin class and the risk of having a reaction is significant so it should be avoided. There is controversy about the risk of cross reaction between class of antibiotics penicillin and cephalosporin (keflex). It appears the risk is low (but not 0). If penicillin allergy was years ago, skin testing for penicillin can help know if it is still there. Allergist can help. ...Read more

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Can I take cephalexin if I am highly allergic to penicillin? I have not taken penicillin since I was very young. Reaction of hives convulsions

Can I take cephalexin if I am highly allergic to penicillin? I have not taken penicillin since I was very young.  Reaction of hives convulsions

Penicillin allergy: You have what is known as an immediate hypersensitivity reaction to penicillin derivatives and should never be given one, since this is life-threatening. There is said to be cross-hypersensitivity reactions to cephalosporins in 5% of pen allergic persons, and 0.1% of these have a severe reaction. My advice would be not to take a cephalosporin antibiotic unless there was no alternative. ...Read more

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Dr. Aaron Milstone
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I am allergic to penicillin is it safe to take cephalexin for infection in the urine.

I am allergic to penicillin is it safe to take cephalexin for infection in the urine.

Yes: Unless you had an anaphylactic reaction to penicillin (major breathing problems) there is little risk to trying cephalexin. ...Read more

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Is it a bad idea for someone allergic to penicillin safely take keflex, a cephalosporin?

Yes: Cephalexin (keflex) is a first generation cephalosporin and a very close cousin to penicillin. Though it is not 100% true that all penicillin allergic individuals are also allergic to cephalexin, there is a high likelihood of that happening. ...Read more

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I'm allergic to penicillin. Was prescribed cephalexin for folliculitis. Stop taking it 3 days ago. Now I have hives all over. Delayed reaction?

Possible: A small % of people who are allergic to penicillin may also react to cephalosporin such as cephalexin. However, if your reaction did not occur until about 10 days after you started to take the medication, this may well be a true allergic reaction specific to cephalexin. ...Read more

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I'm allergic 2 penicillin/prescribed cephalexin 4 a cellulitis infection in my arm from a iv. How fast would a serious reaction occur if allergic ?

I'm allergic 2 penicillin/prescribed cephalexin 4 a cellulitis infection in my arm from a iv. How fast would a serious reaction occur if allergic ?

Quickly: If you are allergic only to penicillin there is about a 10% risk of allergy to Cephalexin a serious reation could involve difficult breathing and falling blood pressure. This could be a medical emergency. A mild reaction might involve a skin rash or hives and though annoying be mild. If you have concerns be sure and discuss it with your physician first. ...Read more

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