Ciprofloxacin

Ciprofloxacin is a fluoroquinolone antibiotic with broad-spectrum bactericidal activity against Gram-negative and some Gram-positive organisms.

It acts by inhibiting bacterial DNA gyrase and topoisomerase IV, enzymes essential for DNA replication, transcription, repair, and recombination.

Ciprofloxacin is licensed for the treatment of a range of infections, including urinary tract infections (UTIs), lower respiratory tract infections, bone and joint infections, gastrointestinal infections (including traveller's diarrhoea caused by enterotoxigenic E.

coli), intra-abdominal infections, and certain sexually transmitted infections.

The BNF notes that ciprofloxacin should be reserved for infections resistant to other antibiotics or when first-line agents are unsuitable, reflecting antibiotic stewardship principles.

The MHRA has issued important safety restrictions for fluoroquinolones (November 2018), advising that they should not be prescribed for mild or self-limiting infections due to the risk of disabling, long-lasting, and potentially irreversible side effects affecting musculoskeletal, nervous, and psychiatric systems.

Ciprofloxacin has excellent oral bioavailability (approximately 70-80%) and achieves therapeutic concentrations in most tissues.

Swallow tablets whole with plenty of water.

Ciprofloxacin may be taken with or without food but should not be taken with dairy products or calcium-fortified beverages, as calcium chelates the drug and reduces absorption by up to 50%.

Similarly, avoid concurrent ingestion of antacids containing aluminium, magnesium, or iron supplements; separate administration by at least 2 hours.

Maintain adequate hydration throughout the course to minimise the risk of crystalluria. Complete the full prescribed course even if symptoms improve.

Do not take double doses if a dose is missed; take the next dose at the scheduled time.

Uncomplicated UTI: 250 mg twice daily for 3 days.

Complicated UTI or pyelonephritis: 500 mg twice daily for 7-14 days.

Lower respiratory tract infections: 500 mg twice daily for 7-14 days.

Gonorrhoea (uncomplicated): 500 mg as a single dose (though ceftriaxone is now preferred first-line per BASHH guidelines).

Bone and joint infections: 500-750 mg twice daily for up to 3 months.

In renal impairment (creatinine clearance 30-60 mL/min), the maximum dose is 500 mg every 12 hours. In severe renal impairment (<30 mL/min), reduce to 250-500 mg every 24 hours.

Elderly patients require no specific dose adjustment but careful renal assessment.

Side effects are categorised per SmPC frequency data.

Common (≥1/100 to <1/10): Nausea, diarrhoea, vomiting, rash, arthralgia.

Uncommon (≥1/1,000 to <1/100): Headache, dizziness, sleep disturbance, taste alteration, abdominal pain, flatulence, dyspepsia, elevated liver transaminases, myalgia, pruritus, superinfection with Candida.

Rare (≥1/10,000 to <1/1,000): Tendinitis and tendon rupture (particularly Achilles tendon), peripheral neuropathy, seizures, photosensitivity, hepatitis, interstitial nephritis, QT prolongation, torsade de pointes, vasculitis, Stevens-Johnson syndrome, Clostridioides difficile-associated diarrhoea.

MHRA safety alert (2018): Fluoroquinolones have been associated with disabling and potentially irreversible adverse reactions affecting tendons, muscles, joints, nerves, and the central nervous system.

These may occur within hours of first dose and persist for months after cessation.

The risk is increased in elderly patients, those with renal impairment, and organ transplant recipients on corticosteroids.

The MHRA has restricted fluoroquinolone use to serious or life-threatening infections where other antibiotics are inappropriate. Do not prescribe for mild, self-limiting infections.

Discontinue immediately at the first sign of tendon pain, swelling, or inflammation; at the first sign of peripheral neuropathy (tingling, numbness, pain); or if psychiatric symptoms develop (anxiety, depression, hallucinations, suicidal ideation).

Avoid in patients with a history of tendon disorders related to fluoroquinolones.

Ciprofloxacin lowers the seizure threshold; use with caution in patients with epilepsy or conditions predisposing to seizures.

Significant CYP1A2 inhibition leads to interactions with theophylline, duloxetine, and tizanidine (contraindicated).

Avoid excessive sun exposure and UV light during treatment and for 48 hours after discontinuation.

Ciprofloxacin is contraindicated in patients with hypersensitivity to ciprofloxacin, other fluoroquinolones, or any excipient.

It must not be co-administered with tizanidine due to clinically significant CYP1A2 inhibition causing elevated tizanidine levels and severe hypotension.

It is contraindicated in children and adolescents (except for specific licensed indications) due to the risk of articular cartilage damage. Use during pregnancy and breastfeeding is contraindicated.

History of tendon disorders with previous fluoroquinolone exposure is a contraindication.