Fish Antibiotics – Step 2: Ciprofloxacin

[Review of series to date:  If you’ve given up on getting your doctor to prescribe extra antibiotics for stockpiling or perhaps merely want to supplement your limited stores, you may be considering the “fish antibiotic” route.  This series of articles in aimed at discussing the value of acquiring specific antibiotics.  You should, of course, make sure the product you intend to acquire is a USP grade A-B rated generic (as discussed elsewhere on this site).  The first article in this series discussed Where to Start: Cephalexin.]

After cephalexin, the second antibiotic I would recommend for your armamentarium is ciprofloxacin (generic form of Cipro).  I choose ciprofloxacin because it complements cephalexin, filling in much of the gap regarding infections for which cephalexin is ineffective.  There are valid arguments for other antibiotics, but I’ll explain my reasoning for this choice further below.

As with cephalexin, ciprofloxacin was truly a wonder drug when first released (1987).  Early on it was nearly 100% effective for urinary tract infections, chronic prostatitis, many pneumonias, gonorrhea, and was one of the few effective oral antibiotics for serious bone infections (osteomyelitis). It has the benefit of being nearly as effective orally as intravenously.

With the overuse in recent decades of this class of antibiotics (the fluoroquinolones), bacterial mutations have emerged, making the microbial population in America increasingly resistant to ciprofloxacin and related antibiotics.  However, as with cephalexin, as the use of antibiotics declines at TEOTWAWKI, bacteria will likely regain their sensitivity to the killing power of this drug.

Not many years ago Cipro cost on the order of $7-10 per pill, but now a 10-day course of treatment with generic ciprofloxacin runs only $4 (from a discount pharmacy), making it quite affordable for stockpiling.  (Note: when sold as a “fish antibiotic” it will likely cost more.)

As I’ve stated before, at TEOTWAWKI antibiotics should be reserved for potentially life-threatening or disabling conditions, as well as highly-communicable diseases.  When Cipro was first released, it was reserved for serious infections, in part due to its high cost.  As the price came down, the use of generic ciprofloxacin exploded, eventually leading to resistance.  The other consequence of widespread use was recognition of unsuspected side-effects.

Any antibiotic, including ciprofloxacin, may have side-effects due to allergy, gastrointestinal (stomach/intestines) intolerance, nausea, diarrhea, rashes, or subsequent yeast or C. diff infection.

However, ciprofloxacin, as well as the other quinolones (Levaquin, Avelox – both expensive), has the unusual potential side-effect of tendon damage or rupture.  As with every antibiotic, there are other serious but rare side-effects.  Since I have not observed the majority of these in decades of using ciprofloxacin, I will omit them here.  (To read about less common side-effects CLICK HERE.) By far the most common side-effects I have seen are ciprofloxacin-related yeast infections and gastrointestinal intolerance.  The occasional patient may exhibit a rash or other sign of allergic reaction, and I’ve seen a handful of patients who have experienced tendon inflammation, but not rupture.  Though the drug carries a “black-box warning” for several potentially serious side-effects, these are quite rare.  The great majority of patients tolerate the drug quite well; still you should be aware that all medications are potential poisons, and if you think you are experiencing anything unusual, it is best to discontinue the medication unless the benefit outweighs the risk.

A few other concerns regarding ciprofloxacin:

  1. Do not give to children under age 16, or to pregnant or nursing mothers unless it is the only option for a life-threatening situation.
  2. Because calcium and antacids interfere with the absorption of the drug, it is best to avoid these minerals while on ciprofloxacin, or at least take the antibiotic between meals.
  3. Resultant yeast infections will usually resolve once the medication is discontinued, whereas C. diff likely won’t (see future installment of this series regarding metronidazole).

As for the benefits, effectiveness against serious illness is the primary reason I choose ciprofloxacin as the second antibiotic to have on hand.  It would not necessarily be first-line for many infections, but is an excellent second-line choice for infection that has not resolved with cephalexin (or possibly with doxycycline, amoxicillin, or trimethoprim-sulfamethoxazole).  Specifically, ciprofloxacin often is effective for resistant skin infections (especially in diabetics), urinary infections (gram negative bacteria), and prostate infections.  If the resistance rate drops back to pre-overuse days, it will also be useful for cephalexin-resistant pneumonia and gonorrhea.

When high blood levels of antibiotics are needed for serious infection, nowadays IV antibiotics are employed.  Ciprofloxacin can provide an equivalent blood concentration even when taken orally.  The two most common serious infections I currently treat with ciprofloxacin are kidney infection and diverticulitis. (A bladder infection is not considered serious unless it evolves into a kidney infection.)  For diverticulitis, ciprofloxacin is (and generally must be) used in combination with a second antibiotic, namely metronidazole (Flagyl).  By using ciprofloxacin, I have been able to keep many patients out of the hospital – and if there’s no hospital to go to, this antibiotic will save many lives.

Ciprofloxacin is also effective against anthrax, but bioterrorism is really the least of my concerns.  After TEOTWAWKI current common infections will most certainly occur commonly.  I’ve never met a doctor who’s treated anthrax, but every family doctor has treated pneumonia, cellulitis, kidney infection, diverticulitis, and infectious diarrhea on a weekly, if not daily, basis.

The usual adult doses of ciprofloxacin for various diseases are listed below.

Anthrax exposure

(inhalation anthrax)

500 mg every 12 hours x 60 days

ASAP after suspected or confirmed exposure

Pediatric dose: 15 mg/kg every 12 hours (max: 500 mg/dose)

Anthrax treatment

(inhalation anthrax)

500 mg every 12 hours x 60 days plus 1 or 2 other antibiotics (rifampin, penicillin, ampicillin, chloramphenicol, imipenem, clindamycin, or clarithromycin)

[start with IV if available]

Anthrax, cutaneous 500 mg every 12 hours x 60 days

(caused by E. coli)

500 mg every 12 hours x 7-14 days
Bladder infection (cystitis) 250 mg every 12 hours x 3 days

(reserve for serious cases or when kidney infection likely to follow)

Bronchitis in patient with significant COPD 500 mg every 12 hours x 7-14 days
Cholera 1 gm single dose with emphasis on fluid replacement (antibiotics optional for cholera)
Diverticulitis 500 mg every 12 hours x 7-14 days

(use with metronidazole)


(patient and partner)

250 mg single dose

(not currently recommended due to high resistance rates)

Joint or bone infection 500-750 mg every 12 hours

for 4-6 weeks

Meningococcal meningitis exposure 500 mg single dose
Pneumonia resistant to first-line antibiotic 500 -750 mg every 12 hours x 7-14 days
Plague, exposure 500 mg every 12 hours x 7 days
Plague, treatment 500 mg every 12 hours x 10 days
Prostatitis, chronic 500 mg every 12 hours x 28 days
Pyelonephritis (kidney infection) 500 mg every 12 hours x 7-14 days

Pediatric dose: 10-20 mg/kg every 12 hours (max: 750 mg/dose)


(infectious diarrhea)

500 mg every 12 hours x 5-7 days
Sinusitis 500 mg every 12 hours x 10 days
Skin or soft tissue 500 mg every 12 hours x 7-14 days


The next installment of this series will focus on doxycycline.

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About Cynthia J. Koelker, MD

CYNTHIA J KOELKER , MD is a board-certified family physician with over twenty years of clinical experience. A member of American Mensa, Dr. Koelker holds degrees in biology, humanities, medicine, and music from M.I.T., Case Western Reserve University School of Medicine, and the University of Akron. She served in the National Health Service Corps to finance her medical education.
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One Response to Fish Antibiotics – Step 2: Ciprofloxacin

  1. David C. says:

    Skip cipro, use levo.

    Very good data show cipro drives resistance within the FQ class. That is part of why levo nearly completely replaced cipro on hospital formularies more than a decade ago.

    Cipro is hydrophilic and small, and a great substrate for drug transporters in pathogens’ cell membranes. Levo is hydrophobic and large, and reaches much higher concentrations in tissues than any of the other FQ’s including cipro. Levo is also almost entirely renally excreted, as opposed to cipro which is only 40% or so.

    When cipro went generic, E. coli resistance to FQ’s skyrocketed. Burke Cunha, MD (Inf. Diseases in OH, probably retired now) published some great work on how even within a class of antibiotics, some members drive resistance and others don’t. His poster child for the former was cipro, and the latter, levo.

    More cipro goes out the intestine, so maybe for diverticulitis it would be a better choice. For everything else, levo is clearly a better choice, and that explains why even after cipro went generic, most urologists in my area still used levo.

    [Reply from Doc Cindy: Many good points here. Bacterial resistance varies greatly between communities, and in NE Ohio, ciprofloxacin still offers good coverage in most cases. I do agree that levofloxacin is a better choice for serious infections, but it remains much more expensive. As with every antibiotic, resistance is driven by overuse. In an era of reduced antibiotic use, ciprofloxacin should regain some of the nearly miraculous effectiveness it exhibited when first release. Thanks for writing.]

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