Ciprofloxacin Actions

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Actions of Ciprofloxacin in details

infoThe action of the drug on the human body is called Pharmacodynamics in Medical terminology. To produce its effect and to change the pathological process that is happening the body and to reduce the symptom or cure the disease, the medicine has to function in a specific way. The changes it does to the body at cellular level gives the desired result of treating a disease. Drugs act by stimulating or inhibiting a receptor or an enzyme or a protein most of the times. Medications are produced in such a way that the ingredients target the specific site and bring about chemical changes in the body that can stop or reverse the chemical reaction which is causing the disease.

Ciprofloxacin is a bactericidal agent which inhibits an essential step in the reproduction of bacterial deoxyribonucleic acid (DNA), the A subunit of DNA gyrase (topoisomerase).

Ciprofloxacin is more potent and has a broader spectrum of activity than nalidixic acid, a non-fluorinated quinolone.

Spectrum: Ciprofloxacin is active against (gram-negative aerobic bacteria). Enterobacteriaceae including Escherichia coli and Citrobacter, Enterobacter, Klebsiella, Proteus, Providencia, Salmonella, Serratia, Shigella, Yersinia spp, Pseudomonas aeruginosa, Hapnia, Edwardsiella, Morganella, Acinetobacter spp, Campylobacter spp, Gardenerella vaginalis, Helicobacter pylori, Legionella spp, Aeromonas, Plesiomonas, Pasteurella multocida and Vibrio spp. Ciprofloxacin has variable activity against Brucella melitensis.

Gram-positive aerobic staphylococci bacteria including penicillinase-producing and nonproducing strains as well as some methicillin-resistant strains are susceptible to Ciprofloxacin. Streptococcus pneumoniae and enterococci are less susceptible to the drug.

Ciprofloxacin is also active against Corynebacterium spp and Listeria monocytogenes.

It exerts bactericidal effect against Pseudomonas spp, Haemophilus ducreyi, H. influenzae, Moraxella (Branhamelia) catarrhalis, Neisseria gonorrhea, N. meningitidis. This is also true to β-lactamase-producing strains of H. influenzae, M. catarrhalis and N. gonorrhea.

Mycobacteria, mycoplasmas, rickettsias, Plasmodium falciparum and Clostridium difficile may be sensitive to Ciprofloxacin. Moderate susceptibility to Ciprofloxacin is exhibited by Chlamydia trachomatis.

Resistance: Bacteroides fragilis, C. difficile, other anaerobic bacteria, Campylobacter spp, non-typhoid Salmonella spp, multi-resistant Salmonella typhii, S. paratyphi and β-lactamase-producing gonococcus are resistant to Ciprofloxacin.

Ciprofloxacin is also inactive against against fungi and the spirochete, Treponema pallidum.

Nocardia asteroides, Ureaplasma urealyticum, are usually considered to be resistant to Ciprofloxacin.

During treatment with Ciprofloxacin, resistant strains of Staphylococcus aureus (including methicillin-resistant strains), P. aeruginosa, Enterobacteriaceae including E. coli and Serratia marcescens were found.

Monotherapy with Ciprofloxacin was reported to have caused the development of mutational resistance in mycobacteria.

Cross-resistance exists between Ciprofloxacin and other fluoroquinolones.

Resistance of Staphylococcus epidermidis to Ciprofloxacin may have been caused by the presence of the drug in sweat.

Effects when Given with Other Antimicrobial Agents: Enhanced effect is exhibited when Ciprofloxacin is given with imipenem against P. aeruginosa. The activity of Ciprofloxacin against S. aureus and P. aeruginosa is enhanced if given with aminoglycosides. The same is true against anaerobic bacteria if given concomitantly with clindamycin or cefotaxime.

Pharmacokinetics: Ciprofloxacin, upon ingestion, is readily absorbed in the gastrointestinal tract. Peak plasma concentration of 2.5 mcg/mL is reached 1-2 hrs after 500 mg oral dose. The oral bioavailability of the drug is about 70%.

Absorption of the drug may be delayed by food but it does not give significant clinical effects. The plasma half-life (t½) of Ciprofloxacin is 3.5-4.5 hrs and may be delayed in patients with end-stage renal disease (8 hrs) and in the elderly. In patients with severe liver cirrhosis, t½ is slightly prolonged.

Ciprofloxacin is 20-40% protein bound. It is widely distributed in body and tissues. It may be seen in the cerebrospinal fluid, 10% in normal meninges, and is able to cross the placenta.

Ciprofloxacin is found to be excreted in breast milk but is mainly excreted in the urine by active tubular secretion and glomerular filtration which may be reduced by probenecid. Other means of elimination include hepatic metabolism, excretion in the bile where high concentration are achieved and transluminal excretion in the intestinal mucosa.

The urinary metabolite of Ciprofloxacin is oxociprofloxacin and primary fecal metabolite is suphociprofloxacin.

Oral Ciprofloxacin is 40-50% and 15% is excreted in the urine as unchanged drug and metabolite, respectively, within a period of 1 day. Fecal excretion involves 20-35% of Ciprofloxacin taken orally.

Few amounts of the drug may be removed by dialysis.

How should I take Ciprofloxacin?

Take Ciprofloxacin only as directed by your doctor. Do not take more of it, do not take it more often, and do not take it for a longer time than your doctor ordered.

Ciprofloxacin comes with a Medication Guide. Read and follow the instructions carefully. Ask your doctor if you have any questions.

Ciprofloxacin works best when there is a constant amount in the blood or urine. To help keep the amount constant, do not miss any doses. Also, it is best to take the doses at evenly spaced times, day and night. For example, if you are to take one dose a day, try to take it at the same time each day.

If you need to take Ciprofloxacin for anthrax infection, your doctor will want you to begin taking it as soon as possible after you are exposed to anthrax.

Swallow the extended-release tablet whole. Do not crush, split, or chew it.

Shake the oral liquid for at least 15 seconds just before each use. The oral liquid has small microcapsules floating in it. These microcapsules may look like bubbles or small beads. Do not chew the microcapsules when you take the oral liquid. Measure the oral liquid with the marked measuring spoon that comes with the bottle.

You may take Ciprofloxacin with or without food. However, Proquin® XR tablets should be taken with a main meal, preferably the evening meal.

Drink plenty of fluids while you are taking Ciprofloxacin. Drinking extra water will help prevent some unwanted effects of Ciprofloxacin.

Do not take Ciprofloxacin alone with milk, yogurt, or other dairy products. Do not drink any juice with calcium added when you take Ciprofloxacin. It is okay to have dairy products or juice as part of a larger meal when you take Ciprofloxacin.

If you are taking aluminum or magnesium-containing antacids, iron supplements, multivitamins, didanosine (Videx®), lanthanum carbonate (Fosrenol®), sevelamer (Renagel®), sucralfate (Carafate®), or any products containing calcium or zinc, do not take them at the same time that you take Ciprofloxacin. It is best to take these medicines at least 2 hours before or 4 to 6 hours after taking Ciprofloxacin. These medicines may keep Ciprofloxacin from working properly.

Keep using Ciprofloxacin for the full treatment time, even if you feel better after the first few doses. Your infection may not clear up if you stop using the medicine too soon.


The dose of Ciprofloxacin will be different for different patients. Follow your doctor's orders or the directions on the label. The following information includes only the average doses of Ciprofloxacin. If your dose is different, do not change it unless your doctor tells you to do so.

The amount of medicine that you take depends on the strength of the medicine. Also, the number of doses you take each day, the time allowed between doses, and the length of time you take the medicine depend on the medical problem for which you are using the medicine.

  • For oral dosage form (extended-release tablets):
    • For uncomplicated urinary tract infections (acute cystitis):
      • Adults—500 milligrams (mg) once a day for 3 days.
      • Children—Use and dose must be determined by your doctor.
    • For complicated urinary tract infections:
      • Adults—1000 milligrams (mg) once a day.
      • Children—Use and dose must be determined by your doctor.
    • For acute uncomplicated pyelonephritis:
      • Adults—1000 milligrams (mg) once a day.
      • Children—Use and dose must be determined by your doctor.
  • For oral dosage forms (suspension or tablets):
    • For infections:
      • Adults—250 to 750 milligrams (mg) two times a day, taken every 12 hours.
      • Children—Use and dose must be determined by your doctor.
    • For urinary tract or serious kidney infections:
      • Adults—250 to 500 milligrams (mg) two times a day, taken every 12 hours.
      • Children—Dose is based on body weight and must be determined by your doctor. The dose is usually 10 to 20 milligrams (mg) per kilogram (kg) of body weight every 12 hours. However, the dose is usually not more than 750 mg per day.
    • For gonorrhea:
      • Adults—250 milligrams (mg) taken as a single dose.
      • Children—Use and dose must be determined by your doctor.
    • For anthrax infection (post-exposure):
      • Adults—500 milligrams (mg) two times a day, taken every 12 hours.
      • Children—Dose is based on body weight and must be determined by your doctor. The dose is usually 15 milligram (mg) per kilogram (kg) of body weight every 12 hours. However, the dose is usually not more than 500 mg per day.

Missed Dose

If you miss a dose of Ciprofloxacin, take it as soon as possible. However, if it is almost time for your next dose, skip the missed dose and go back to your regular dosing schedule. Do not double doses.

Do not take more than one extended-release tablet each day.


Keep out of the reach of children.

Do not keep outdated medicine or medicine no longer needed.

Ask your healthcare professional how you should dispose of any medicine you do not use.

Store the medicine in a closed container at room temperature, away from heat, moisture, and direct light. Keep from freezing.

You may store the oral liquid at room temperature or in the refrigerator. Do not freeze the bottle. Do not keep the mixed oral liquid for more than 14 days. Throw away any unused liquid after 14 days.

Ciprofloxacin administration

infoAdministration of drug is important to know because the drug absorption and action varies depending on the route and time of administration of the drug. A medicine is prescribed before meals or after meals or along with meals. The specific timing of the drug intake about food is to increase its absorption and thus its efficacy. Few work well when taken in empty stomach and few medications need to be taken 1 or 2 hrs after the meal. A drug can be in the form of a tablet, a capsule which is the oral route of administration and the same can be in IV form which is used in specific cases. Other forms of drug administration can be a suppository in anal route or an inhalation route.

Use this medication exactly as prescribed by your doctor. Do not use it in larger amounts or for longer than recommended. Follow the directions on your prescription label.

Otic medications are for use only the ear. Do not take Ciprofloxacin otic by mouth or apply it to the skin.

Wash your hands before using this medication.

Ciprofloxacin otic comes in single-use containers. Each container has enough medicine in it for one dose.

Before using the medication, warm the container by holding it in your hands for at least a minute. Using Ciprofloxacin otic that is cold may cause dizziness when you place the medicine into your ear.

To use the ear drops, lie down with your ear facing upward. Pull back on your ear gently to open up the ear canal. If giving this medicine to a child, pull down on the earlobe to open the ear canal. Empty all of the medicine from the container into the ear and stay lying down for at least 1 minute longer.

If you are treating both ears, repeat the instructions above using a second container of Ciprofloxacin otic.

Ciprofloxacin should be used 2 times daily for 7 days, unless your doctor tells you otherwise. Your doses should be spaced at least 12 hours apart.

Each single-use container of this medicine is for one use only. Throw away the container after one use, even if there is still some medicine left in it.

Use this medication for the full prescribed length of time. Your symptoms may improve before the infection is completely cleared. Call your doctor if your infection does not improve after using Ciprofloxacin otic, or if your symptoms get worse.

Store this medication at room temperature away from moisture, heat, and light. Keep each single-use container in the foil pouch until you are ready to use the medication.

Ciprofloxacin pharmacology

infoPharmacokinetics of a drug can be defined as what body does to the drug after it is taken. The therapeutic result of the medicine depends upon the Pharmacokinetics of the drug. It deals with the time taken for the drug to be absorbed, metabolized, the process and chemical reactions involved in metabolism and about the excretion of the drug. All these factors are essential to deciding on the efficacy of the drug. Based on these pharmacokinetic principles, the ingredients, the Pharmaceutical company decides dose and route of administration. The concentration of the drug at the site of action which is proportional to therapeutic result inside the body depends on various pharmacokinetic reactions that occur in the body.

Mechanism of Action

Ciprofloxacin is a member of the fluoroquinolone class of antibacterial agents.



When Ciprofloxacin is administered with food, approximately 87% of Ciprofloxacin is gradually released from the tablet over a 6-hour period. When administered following a meal maximum plasma Ciprofloxacin concentrations are attained approximately 4.5-7 hours after dosing with Ciprofloxacin (Ciprofloxacin hcl) tablets. Ciprofloxacin (Ciprofloxacin hcl) should be administered with a main meal of the day, preferably the evening meal; if Ciprofloxacin (Ciprofloxacin hcl) is given while fasting, the bioavailability will be lowered substantially. Administration of Ciprofloxacin (Ciprofloxacin hcl) with a standardized meal (1000 calories, 50% fat) increased the Cmax and AUC0-24h by approximately 120% and 170%, respectively, compared to administration under fasting conditions; the mean Tmax was prolonged from 2.3 hours to 4.5 hours. Table 2 presents the pharmacokinetic parameters obtained at steady state for Ciprofloxacin 500 mg once daily versus Ciprofloxacin immediate-release tablets 250 mg twice daily.

Table 2: Steady-State Pharmacokinetics for Ciprofloxacin in Plasma of Healthy Subjects (Day 3).

Activity in vitro and in vivo

Ciprofloxacin has in vitro activity against a wide range of gram-negative and gram-positive organisms. Ciprofloxacin is less active when tested at acidic pH. The inoculum size has little effect when tested in vitro . The minimal bactericidal concentration (MBC) generally does not exceed the MIC by more than a factor of 2.

Ciprofloxacin has been shown to be active against most strains of the following organisms, both in vitro and in clinical infections as described in the INDICATIONS AND USAGE section.

Aerobic gram-negative microorganisms

Escherichia coli

Klebsiella pneumoniae

The following in vitro data are available, but their clinical significance is unknown:

Ciprofloxacin exhibits in vitro MICs of 1 mcg/mL or less against most ( > 90%) strains of the following microorganisms; however, the safety and effectiveness of Ciprofloxacin (Ciprofloxacin hcl) in treating clinical infections due to these microorganisms have not been established in adequate and well-controlled clinical trials.

Aerobic gram-negative microorganisms

Proteus mirabilis

Susceptibility Tests

Interpretive criteria for urinary isolates have not been established for Ciprofloxacin. Interpretive criteria established based on systemic drug levels may not be appropriate for uncomplicated urinary tract infections.

  • Dilution Techniques: Quantitative methods are used to determine antimicrobial minimum inhibitory concentrations (MICs). These MICs provide estimates of the susceptibility of bacteria to antimicrobial compounds. The MICs should be determined using a standardized procedure. Standardized procedures are based on a dilution method1 (broth or agar) or equivalent with standardized inoculum concentrations and standardized concentrations of Ciprofloxacin powder. The MIC values should be interpreted according to the criteria outlined in Table 4.
  • Diffusion Techniques: Quantitative methods that require measurement of zone diameters also provide reproducible estimates of the susceptibility of bacteria to antimicrobial compounds. One such standardized procedure 2 requires the use of standardized inoculum concentrations. This procedure uses paper disks impregnated with 5-mcg Ciprofloxacin to test the susceptibility of microorganisms to Ciprofloxacin.

    Reports from the laboratory providing results of the standard single-disk susceptibility test with a 5-mcg Ciprofloxacin disk should be interpreted according to the f criteria outlined in Table 4. Interpretation should be as stated above for results using dilution techniques. Interpretation involves correlation of the diameter obtained in the disk test with the MIC for Ciprofloxacin.

Table 4: Susceptibility Interpretive Criteria for Ciprofloxacin

Pathogen Minimum Inhibitory Concentrations (mcg/mL) Disk Diffusion (zone diameter in mm)
Enterobacteriaceae ≤ 1 2 ≥ 4 ≥ 21 16-20 ≤ 15
S=Susceptible, I=Intermediate, and R=Resistant

A report of “Susceptible” indicates that the pathogen is likely to be inhibited if the antimicrobial compound in the blood reaches the concentration usually achievable. A report of “Intermediate” indicates that the result should be considered equivocal, and if the microorganism is not fully-susceptible to alternative, clinically feasible drugs, the test should be repeated. This category implies possible clinical applicability in body sites where the drug is physiologically concentrated or in situations where high dosage of drug can be used. This category also provides a buffer zone which prevents small uncontrolled technical factors from causing major discrepancies in interpretation. A report of “Resistant” indicates that the pathogen is not likely to be inhibited if the antimicrobial compound in the blood reaches the concentration usually achievable; other therapy should be selected.

  • Quality Control:

    Standardized susceptibility test procedures require the use of laboratory control microorganisms to control the technical aspects of the laboratory procedures. For dilution technique, standard Ciprofloxacin powder should give the MIC values provided in Table 4. For diffusion technique, the 5 mcg Ciprofloxacin disk should provide zone diameters provided in Table 5.

Table 5: Quality Control for Susceptibility Testing

Microorganism Microorganism QC Number MIC (mcg/mL) Disk Diffusion (zone diameter in mm)
Escherichia coli ATCC 25922 0.004-0.015 30-40
Staphylococcus aureus ATCC 29213 0.12-0.5 Not applicable
Staphylococcus aureus ATCC 25923 Not applicable 22 – 30

Animal Pharmacology

Gastrointestinal or other toxic effects were not observed in male and female beagle dogs following oral administration of Ciprofloxacin (Ciprofloxacin hcl) tablets at doses up to 1,000 mg/day for 28 consecutive days (approximately 3 and 5 times the human therapeutic dose based upon AUC comparisons to male and female dogs, respectively).

Ciprofloxacin and other quinolones have been shown to cause arthropathy in immature animals of most species tested.

Crystalluria, sometimes associated with secondary nephropathy, occurs in laboratory animals dosed with the fluoroquinolone class of drugs. This is primarily related to the reduced solubility of Ciprofloxacin under alkaline conditions, which predominate in the urine of test animals. In contrast, crystalluria is rare in man since human urine is typically acidic.

In mice, concomitant administration of nonsteroidal anti-inflammatory drugs such as phenylbutazone and indomethacin with quinolones has been reported to enhance the CNS stimulatory effects of quinolones.

Ocular toxicity seen with some related drugs has not been observed in Ciprofloxacin-treated animals. There was no indication of ocular toxicity in the dog study cited above.

Clinical Studies

Uncomplicated Urinary Tract Infections

Ciprofloxacin (Ciprofloxacin hcl) was evaluated for the treatment of uncomplicated urinary tract infections (acute cystitis) in a randomized, double-blind, controlled trial conducted in the US. This study compared Ciprofloxacin 500 mg once daily for 3 days with Ciprofloxacin immediate-release tablets. Of the 1,037 patients enrolled, 524 were randomly assigned to the Ciprofloxacin (Ciprofloxacin hcl) treatment group and 513 were randomly assigned to the control group. A total of 272 (52%) patients in the Ciprofloxacin (Ciprofloxacin hcl) group and 251 (49%) in the control group were evaluable for efficacy and included in the Per-Protocol population. The primary efficacy variable was bacteriologic eradication of the baseline organism(s) with no new infection at the Test-of-Cure (TOC) visit (Day 4 to 11 post-therapy).

The bacteriological eradication and clinical success rates were similar for both treatment groups. The eradication and clinical success rates and their corresponding 95% confidence intervals for the differences between rates (Ciprofloxacin minus control group) are given in Table 6.

Table 6: Bacteriological Eradication and Clinical Cure Rates at the Test-of-Cure (TOC) Visit

Ciprofloxacin 500 mg once daily for 3 days Ciprofloxacin immediate- release tablet 250 mg twice daily for 3 days
qd x 3 Days bid x 3 Days
Randomized Patients 524 513
Per Protocol Patients 272 (52%) 251 (49%)
Bacteriologic Eradication with no new infection at TOC 212 / 272 (78%) 193 / 251 (77%)
Clinical Response at TOC 233 / 272 (86%) 216 / 251 (86%)
Bacteriologic Eradication by organism*
E. coli 211 / 222 (95%) 184 / 202 (91%)
K. pneumoniae 11 / 12 (92%) 10 / 13 (77%)
*Number of patients with specified baseline organism eradicated /Number of per-protocol patients with specified baseline organism.

The bacteriological eradication rates for baseline organisms at the TOC visit were 93% (254/272) for Ciprofloxacin and 90% (225/251) for Ciprofloxacin immediate-release tablets. Of the patients with their baseline organism eradicated, new infections were detected in 42/254 (16%) Ciprofloxacin-treated patients and 32/225 (14%) Ciprofloxacin-treated patients at the TOC visit. Gram-negative rods were responsible for new infections in 10 Ciprofloxacin-treated patients and 7 Ciprofloxacin-treated patients, and Enterococcus species were isolated in 24 Ciprofloxacin-treated patients, and 20 Ciprofloxacin-treated patients.


Clinical and Laboratory Standards Institute. Methods for Dilution Antimicrobial Susceptibility Tests for Bacteria That Grow Aerobically. Eight Edition. Approved Standard CLSI Document M7-A8, Vol. 29, No. 2, CLSI, Wayne, PA, January, 2009.

Clinical and Laboratory Standards Institute. Performance Standards for Antimicrobial Disk Susceptibility Tests. Tenth Edition. Approved Standard CLSI Document M2-A10, Vol. 29, No. 1, CLSI, Wayne, PA, January, 2009.


  1. DailyMed. "CIPROFLOXACIN; DEXAMETHASONE: DailyMed provides trustworthy information about marketed drugs in the United States. DailyMed is the official provider of FDA label information (package inserts).". (accessed September 17, 2018).
  2. NCIt. "Ciprofloxacin: NCI Thesaurus (NCIt) provides reference terminology for many systems. It covers vocabulary for clinical care, translational and basic research, and public information and administrative activities.". (accessed September 17, 2018).
  3. EPA DSStox. "Ciprofloxacin: DSSTox provides a high quality public chemistry resource for supporting improved predictive toxicology.". (accessed September 17, 2018).


The results of a survey conducted on for Ciprofloxacin are given in detail below. The results of the survey conducted are based on the impressions and views of the website users and consumers taking Ciprofloxacin. We implore you to kindly base your medical condition or therapeutic choices on the result or test conducted by a physician or licensed medical practitioners.

User reports

2 consumers reported administration

When best can I take Ciprofloxacin, on an empty stomach, before or after food? website users have also released a report stating that Ciprofloxacin should be taken With a meal. In any case, this may not be the right description on how you ought to take this Ciprofloxacin. Kindly visit your doctor for more medical advice in this regard. Click here to see other users view on when best the Ciprofloxacin can be taken.
With a meal1
After food1

Consumer reviews

Elias08 May 2015 09:45
its hard to find. have been to so many chemists all in vain

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Information checked by Dr. Sachin Kumar, MD Pharmacology

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