Overview
Ciprofloxacin is a widely utilized, potent fluoroquinolone antibiotic. While it possesses a broad spectrum of activity, it is particularly distinguished by its exceptional efficacy against Gram-negative bacteria, including challenging pathogens like Pseudomonas aeruginosa. Due to concerns over rising resistance and its side effect profile, its use is increasingly reserved for infections where other antibiotics are ineffective or inappropriate. Common indications include complicated urinary tract infections, acute pyelonephritis, chronic bacterial prostatitis, severe infectious diarrhea, typhoid fever, and bone and joint infections. It is also used for post-exposure prophylaxis of inhalational anthrax.

Mechanism of Action
Ciprofloxacin exerts a rapid bactericidal effect by specifically targeting bacterial DNA gyrase (topoisomerase II) and topoisomerase IV. These enzymes are absolutely essential for the uncoiling, replication, and repair of bacterial DNA. By inhibiting these enzymes, ciprofloxacin effectively halts DNA synthesis, preventing bacterial cell division and causing rapid death of the microorganism. Its unique mechanism makes it effective against bacteria that have developed resistance to other classes of antibiotics, such as beta-lactams or macrolides.

Dosage and Administration
For adults, the oral dosage typically ranges from 250 mg to 750 mg every 12 hours, depending on the severity and nature of the infection. For example, a standard dose for a complicated UTI might be 500 mg every 12 hours for 7 to 14 days, while bone infections may require 750 mg every 12 hours for several weeks. It is critical that ciprofloxacin is not taken concurrently with dairy products (like milk or yogurt) alone or calcium-fortified juices, as calcium significantly reduces its absorption. It must also be separated by at least 2 hours from antacids, iron supplements, and zinc.

Side Effects and Risks
Ciprofloxacin shares the severe “black box warnings” common to all fluoroquinolones. These include a heightened risk of tendinitis and tendon rupture (most notably the Achilles tendon), peripheral neuropathy, and severe central nervous system effects (such as confusion, hallucinations, and a lowered seizure threshold). It can also cause QT interval prolongation and carries a risk of severe Clostridioides difficile-associated diarrhea. More common, milder side effects include nausea, diarrhea, dizziness, and photosensitivity (increased susceptibility to severe sunburns).

Contraindications
It is strictly contraindicated in patients with a known hypersensitivity to ciprofloxacin or other fluoroquinolones. Co-administration with tizanidine is contraindicated due to severe hypotensive and sedative effects. It should be avoided in patients with a history of myasthenia gravis, as it may exacerbate muscle weakness. Caution is required in patients with known CNS disorders that predispose to seizures, and in those with known QT prolongation. Dose adjustments are necessary for patients with impaired renal function.

Pregnancy and Lactation
The use of ciprofloxacin during pregnancy is generally avoided unless the potential benefit clearly outweighs the risks. Similar to other fluoroquinolones, animal studies have demonstrated cartilage damage in weight-bearing joints of juvenile animals, raising concerns for fetal development. It is excreted into human breast milk. Because of the potential for serious adverse reactions, including cartilage damage, in nursing infants, breastfeeding is not recommended during treatment with ciprofloxacin.