Overview

Keflex belongs to a class of potent antibiotics called cephalosporins. It is one of the first of these to become available generically and is now often prescribed as cephalexin.

This drug works against a wide variety of germs, including those that cause infections of the skin, lungs, throat, prostate, urinary tract, bones, and ears.

Cephalosporins are broad spectrum medicines that were originally discovered in one of the world’s most unlikely locations.

A fungus found close to a sewer outlet along the coast of Sardinia turned out to cure a number of nasty infections. From this chance observation many extraordinary antibiotics have been developed.

Side Effects and Interactions

Side effects from cephalosporin-type antibiotics are generally mild. Nevertheless, cephalexin can cause a range of digestive tract disorders.

Indigestion, stomach pain, nausea, vomiting and diarrhea have been reported. If diarrhea becomes severe contact your physician, as it may be a warning of drug-induced colitis.

Other infrequent reactions to be aware of include rash, itching, vaginitis, headache, confusion, joint pain, fatigue and dizziness.

Cephalexin may affect laboratory test results. Liver enzymes may become elevated and false-positive results may show up during certain diabetes tests. Make sure that the laboratory personnel are aware you are taking cephalexin if you have blood drawn.

And remember to report any symptoms or suspected side effects of cephalexin to your physician promptly.

Special Precautions

If you are allergic to penicillin-type antibiotics, alert your physician immediately. Some people who are sensitive to penicillin may also react to cephalexin.

Symptoms such as breathing difficulty, wheezing, sneezing, hives, itching, and skin rash require immediate emergency treatment.

Life-threatening anaphylactic shock may produce an inability to breathe and cardiovascular collapse and can occur within minutes of exposure.

People with kidney problems should receive cephalexin only under careful medical supervision as the dosage will most likely have to be modified to prevent toxicity.

Taking the Medicine

Although this antibiotic is absorbed more efficiently when it is taken on an empty stomach, the pills can be swallowed with food, especially if they upset your stomach.


 

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  1. cristina
    UK
    Reply

    This drug has made me psychotic as did norfloxacillin many years ago. Came down 2 months ago with such severe pain on top of my left hip that I couldn’t stand and was nearly passing out. Hospital put me on an anti-biotic and rehydrating drips. Tests on urine showed UTI and ultrasound showed absence of passing a kidney stone.

    Was put on course of flufloxacillin. Doctor back home tested urine which still showed nitrates (sign of infection) and put me on a course of keflex. Have finished course 10 days ago and still got UTI and the symptoms mentioned in above comments (nightmares, feeling of impending doom, getting stuck in negative thought patterns, insomnia but no digestive problems) have not faded.

    Have refused to take a take a fourth course of antibiotics so am going to exist on a diet of pure cranberry juice, steamed vegetables with live yoghurt and probiotic pills for 6 days then have my urine tested again. Have not slept for more than 14 days ago despite taking mild medication to help me. Friends say I look like death warmed up. How long will the side effects subside? I will tell you if my home grown treatment works.

  2. Nicki
    Portland Oregon
    Reply

    I took this for my cyst everything was going smoothly. Until I got major headaches and the light bothered me. Then I would fall into a deep sleep and wake up with confusion feeling numb. So I went back to the doctor and she said I’m fine and to take Advil.

    OKAY I did and then I got brain fog and woke up again not knowing where I was so my sisters rushed me to the hospital. 4 hours later my doctor tells me I’m fine and to finish pills 500 mg and to take 600 mg of ibuprofen :( finally I asked him about my symptoms, and he told me that the pill only causes diarrhea or stomach aches and I may be going to sleep with a migraine, actually, he said he doesn’t know. I told him I am not going to finish my medicine and I will find a new doctor. But the new doctor prescribed me Bactrim as well. Why oh why do they stick pills down clients throats – I’ll never understand.

  3. Ron W
    Michigan
    Reply

    It’s not the drugs its the doctors with ADD. Sent home from hospital with cloudy urine and negative bacteria. Urine progresses to a light cider mill apple juice cloudiness. In hospital (different one) UTI positive, injection of antibiotic, and sent home on keflex 500 four times a day.

    Second doctor told me I was taking it wrong (500 every three hours) should take two five hundreds every twelve hours and just started. Have ileostomy (from UC). with chronic obstruction, Since keflex unbelievable weakness on top of my chronic fatigue, bloating, pain, aches, numbness of left face. MRI taken of head normal but have trigeminal “neuropathy” nor neurolga (means pain). I am told its possibly from either diabetes, infection, or tumor after MRI. Appointment with specialist soon,, Meanwhile mostly left side aches in shoulder, stoma area (hernias), knees, wrists, finger joints, abdominal pain around stoma incessant.

    Second doctor wants me to continue and extend use of keflex as I am 69, I have stage 3 CKD and renal doc says it will not affect my kidney. I am miserable and feel I have a alien in my belly which is full of hernias, taking miralax, disgestive enzymes. Other conditions HBP. Osteoporosis, Sciatica, and spinal degeneration.

    Though diabetic its under good control but I am peeing often (distended bladder). Temperature ranges from 97 to 99. Very achy and feel I have an infection. Urine now clear and yellow. Would like to hear from ileostmate who may have similar problems. I am hoping to have surgery soon to correct chronic pain from adhesions and partial obstruction of ileum though I am told this will be risky. Cannot take the cramps from blockage much more so I am willing to take the risk.

    Keflex seems to have added gasoline to the fire but I am told UTIs can be very dangerous and can lead to kidney infections, failure as well as bone infections. Scared as I have a history of sepsis from UTI as well as ventral incision MRSA.

  4. fenella
    cda
    Reply

    Started taking this drug pre-surgery and have continued. Can’t tolerate it enough to be able to finish it. The chest and abdomen pain is constant, burning and I feel so sick but can’t vomit. It’s really horrible. Also have a chest infection and the coughing brings the nausea up. Never, ever consuming this drug again.

  5. jd
    Reply

    I am also glad for finding this site. I’m having the same vaginal issues and it began the day before I had to take the last pill. Irritation is unbearable and swelling smh… How can I get comfort?

  6. ART
    Reply

    So I was prescribed this medicine when I had a infection in one of my testicles, after a couple of days later it went away, and everything is fine, then one day I woke up with a rash near my penis and I still have it.
    I’ve put cream on it (mostly eczema cream and neosporin ) and yet when I wake up the next day, it’s still all flakey and rash like. Now after 6 days of being off the medicine, I wake up at 2, 3, 4 o’ clock in the morning feeling sick and feeling like I have to throw up, but never do. Couple this be depression? I’ve been a little depressed lately over a health issue. Could it be Allergies?
    I’ve also been constipated, my poop has been coming out in balls. If this is all from the medicine, never taking it again.

  7. LP
    Reply

    Steroids are contraindicated when one has an infection!

  8. Barbara C
    Reply

    Wish I had not waited so long to check this site. This is all very scary for me. Just had breast cancer day surgery last Tuesday and was given a prescription for CEPHALLEXIN; 500mg 3 times daily. Just 2 days left. I felt great after surgery (Lumpectomy plus 2 lymph nodes)except sore throat and congestion from surgery.
    But these last few days my chest feels congested, I feel drained of energy. Despite feeling worse instead of better I continued to take the meds because I was afraid of pneumonia or infection of some kind. I am not taking any more. I am supposed to be walking 3 times a day but my heavy feeling chest, general all over achy painy feeling, and lack of energy is making it difficult. Of course the TERRIBLE POLLUTED AIR is no help either. My back has been getting very itchy now, too.
    (And I thought since the pathology report said no cancer in lymph nodes or margins that everything was okay. But the radiology oncologist pointed out to me that I had INVASIVE DUCTILE CARCINOMA that is HORMONE DEPENDENT, that I had CANCER. The cancer had grown through the duct into the breast. He said he might be able to cut the treatments down to four but first I needed to see the medical oncologist to probably be put on a hormone blocker type med and for me to stop wearing my patch that I was only feeding the cancer! If I did that, I could possibly opt out of radiation treatments since I am 75.)

  9. DS
    Reply

    So, back in the day as a child I had an odd reaction to an old school cephalosporin where my stomach got really hard & painful & I was unable to eat because food would come right back up. As an adult I have taken Keflex a couple of times with no issues. This past Friday my PCP put me on Keflex for an infected cyst that is unable to be removed until the infection is gone. A short time after taking my 1st dose I developed an uncomfortable feeling behind my sternum, almost as if something was caught in my esophagus or like my esophagus was stuck in a muscle spasm. I have had this feeling ever since my 1st dose on Friday and it is only gone when I wake up in the morning but returns after my morning dose. The feeling goes away for a bit when I eat or if I take a deep breath and hold it for a while and slowly exhale. Some times the pressure is so bad it feels like I am going to gag or throw up. It seems like a rather odd reaction to a medication. Has anyone else experienced this with a cephalosporin? What are the odds it’s something totally unrelated to me taking this antibiotic?

  10. TH
    Reply

    Thank God I found this site! I thought I was losing my mind when 2 days after stopping Keflex I began to experience vulva itching and swelling. I knew it wasn’t an STD as I’ve been married forever and had just had a normal pelvic exam only a few weeks ago.
    At first I thought maybe it could have been a reaction from the Florastor probiotic I’m taking to prevent C Diff. But now I’m realizing from all the comments here that it’s the Keflex! I will never take this antibiotic again.
    To help with the itch and a “dry” patch on the skin I began rubbing Manuka Honey 18+ on it. It’s a bit pricey, but I use that stuff for everything…it’s awesome. It’s been 3 days and it’s soooo much better, I can at least function now.

  11. td
    Reply

    I have taken Keflex many times. It ALWAYS gives me thrush and a yeast infection. It usually but not always gives me diarrhea. I just take an Imodium with every dose. This time I was taking it for phlebitis. I got exhausted where I just didn’t want to move. Taking with probiotics helps.

  12. ht
    Reply

    I took this for cystitis but I had a terrible reaction to the tablets last night. I felt the same feeling just a little the night before but didn’t think much of it and contd the tablets yesterday.
    Well, I paid for it. Muscle spasms, on a super high, body wouldn’t relax, diarrhoea, nausea (after taking every tablet), weakness, brain fog and no sleep til 4am for 20 mins when the reaction lessened a bit. Scary as and feeling awful today, to be expected, and I won’t be taking the last 3 tablets. I went with this brand because I had no reaction to it 8 years ago. I’ve had joint pain too, and stool problems (constipation) which ended up in diarrhoea last night – didn’t realise it could be from this.

  13. Diane
    Reply

    Hello, I found this site after looking for a relationship between Keflex and herpes. I took Keflex and within three days had a huge cold sore break out on my mouth. This sore had been dormant for about 15 years! I was sure there was some cause and effect from the drug and now it seems accurate.

  14. BKO
    Reply

    Been taking generic cephalexin for the past four days to prevent possible infection after having knee surgery. I noticed the last few days that I have been feeling light headed, dizzy and nauseous about a half hour or so after taking my meds. Today I decided to take each med independently. I started out first today with the cephalexin and sure enough about a half hour later I started to feel dizzy and nauseous. Additionally my back has been itching uncontrollably over the last couple days. I am fairly certain that it is the generic keflex (cephalexin). The other meds I have taken before without any side effects. Though I rarely take medications this is the first time I have ever had a noticeable negative reaction.

    • Bill C
      Chicago
      Reply

      I have been off this drug for 7 days. I feel miserable. I have all the same side effects. Have you felt relief? If so, how long did it take?

      Thanks!

  15. KE
    Reply

    I started a course of this drug on Mon @ one capsule x 4/day to address a possible infection at my breast. (Total consumed as of 2/21/14 = 14) By day 2, I noticed less burning and pain at said breast, as well as a decrease with swelling, HOWEVER, I began experiencing chest, shoulder and lower back pain (muscle versus joint or so I think) almost at once. My breathing has been shallow at times, to the point of having to sigh in order to get a full inhlation, although this has been intermittent.
    My vagina has been tingling as if a yeast infection is about to begin. I have had a sore throat and a headache. I have also had typical intestinal issues (gas, bloating and increased stools). I called my PCP and spoke with him via a RN and PA… uh, yes. Anyway, he said I should stop taking the med at once and monitor my course over the weekend. All I know is that my body is out of sorts and that it feels quite foreign at this point. This drug and the quick fire presentation that has resulted in response to my taking it are a serious concern for me. This med is a definite no go as far as I am concerned. I am posting so that others might be helped.

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