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Dr. Tharun
Dr. Tharun, Urology Resident
Category: Urology
Satisfied Customers: 3682
Experience:  MBBS, DNB surgery and presently working as Urology resident towards the degree of Urologist.
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Prophylactics for UTIs

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My urologist prescribed 100mg of Nitrofurantoin as a prophylactic against UTI's with catheter use. I have been on this dosage since March 20th when I resumed using catheters twice a day.


I felt some shortness of breath last week (probably due to the 100 degree plus weather and stress), but being that I was only on the medication for less than three months, I would not think that the symptoms were due to the Nitrofurantoin and pulmonary side effects it can cause because from what I have read chronic effects due not occur until at least 6-8 months. Nevertheless, based on a reporting of my condition on-line to my doctor, she switched me over to 500 mg of Keflex daily today via a call for her nurse.


What is your view on the use of Nitrofurantoin versus Keflex (Cephalexin) for the prevention of UTI with catheter use, based on their safety; their effectiveness if preventing UTI while using catheters (and still retaining relatively large volumes of urine; e.g., 300 ml); and their profile in bacteria not easily becoming resistant to the medication?


And is 500 mg excessive? Appears the usual dosage a prophylactic is 250 mg. Perhaps she prescribed a higher dosage due to my level of urinary retention? Thank you.


Cephalexin is a proper antibiotic while nitrofurantoin is just an urinary anti septic and hence will be more effective than nitrofurantoin. Side effect profile is also not very serious.

500 is the regular dose and may be overkill for long times. But initial loading has to be full dose to prevent resistance. After 7- 10 days it can be taken at half dosage as prophylactic one.

Only if you have break through infection while on cephalexin (250) , you may be required to take full dose as prophylaxis.

I hope this answers your question.


Customer: replied 3 years ago.

Appreciate the dosage information on Cephalexin, but my pharmacist and the literature state that Nitrofuratoin is a first-line drug for prophylaxis against UT, and the one most recommended for that purpose.


In fact, the European Association of Urology states that Cephalexin and quinolines should be restricted to specific indicators. These antibiotics cause resistant strains in the fecal flora and potentially subsequent resistant UTI's.


My pharmacist said Nitrofuratoin was specific for UTI's while Keflex was more broad spectrum. She stated that resistance is much more likely to occur with the Keflex.


My reservation about Nitrofuratoin is the potential, though rare, pulmonary and liver damage. Enough to warrant using Keflex instead?


Customer: replied 3 years ago.

"Cephalexin is a proper antibiotic while nitrofurantoin is just an urinary anti septic and hence will be more effective than nitrofurantoin. Side effect profile is also not very serious."


Could you rewrite this please? Which medication is just an urinary antispectic? Thank you.

Customer: replied 3 years ago.

What do you mean by regular dose when referring to 500 mg? The recommended dose for the treatment of most types of bacterial infections is Keflex 250 mg to 1000 mg, taken four times a day for 7 to 14 days.


Nitrofurantoin is preferred because it is effective only in an urinary infection and this is its only use in medical field.Nitrofurantoin has been associated with urinary infection since then.It is not active against any other infection.So sometimes it is referred as urinary antiseptic.

Although it is popular , it doesn't mean it is better than other antibiotics available.If it is effective in preventing UTI without causing side effects, it is the best option.Since you have some breathlessness there is no point in taking the risk of continuing the drug.

Prophylactic dosage is the minimal dosage which will do the work for you of preventing the infection.Usually it is given 500 four times a day for full fledged infection.Either 250 or 500 can be given for prophylaxis depending upon the weight , risk factors , sex , age etc.

Another drug which is used is cifixime 200 mg once a day.

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