Levofloxacin

BRAND NAMES

Levofloxacin is marketed under several brand names worldwide, including Levaquin, Tavanic, and Cravit, which are the most commonly used oral and injectable forms. For eye-related infections, it is also available under ophthalmic brands such as Oftaquix and Quixin. These brands all contain the same active ingredient but may vary by manufacturer and region.

MECHANISM OF ACTION

Levofloxacin works by inhibiting two essential bacterial enzymes: DNA gyrase (topoisomerase II) and topoisomerase IV. These enzymes are required for normal bacterial DNA replication, repair, and cell division. By blocking DNA gyrase, levofloxacin prevents the relaxation of supercoiled bacterial DNA, and by inhibiting topoisomerase IV, it stops the separation of replicated bacterial chromosomes. As a result, bacterial DNA cannot be properly copied or segregated, leading to disruption of cell division and ultimately bacterial cell death.

PHARMACOKINETICS

Absorption

Levofloxacin is well absorbed after oral administration, with an oral bioavailability of about 99%, meaning almost the entire dose reaches systemic circulation.

Distribution

Levofloxacin is widely distributed in the body after absorption and penetrates well into tissues and body fluids such as the lungs, kidneys, prostate, skin, and urine. It has low to moderate plasma protein binding and achieves good concentrations at infection sites, which helps it act effectively against bacteria in different parts of the body.

Metabolism

Levofloxacin undergoes minimal metabolism in the body. Most of the drug remains unchanged after administration, meaning it is not extensively broken down by liver enzymes.

Elimination

Levofloxacin is mainly eliminated through the kidneys, with about 80–90% of the drug excreted unchanged in the urine. A small amount is removed through feces. It has a half-life of around 6 to 8 hours, allowing once-daily dosing. In patients with kidney problems, dose adjustment is needed to prevent accumulation in the body.

PHARMACODYNAMICS

Levofloxacin shows concentration-dependent bactericidal activity, meaning its killing effect increases as drug concentration rises above the minimum inhibitory concentration (MIC). It also has a post-antibiotic effect, where bacterial growth remains suppressed even after drug levels decrease. Its main pharmacodynamic action is inhibition of DNA gyrase and topoisomerase IV, which stops bacterial DNA replication and leads to cell death.

ADMINISTRATION

Levofloxacin is administered either orally or intravenously (IV)depending on the severity of the infection and the patient’s condition. The oral form is available as tablets or solution and is usually taken once daily, with or without food, but should be taken with plenty of water. The IV form is given in hospitals through slow infusion into a vein, typically over 60 to 90 minutes to reduce the risk of side effects.

DOSAGE AND STRENGTH

Levofloxacin is available in different strengths depending on the formulation. Oral tablets are commonly available in 250 mg, 500 mg, and 750 mg strengths, while intravenous (IV) preparations are typically available as 500 mg/100 mL or 750 mg/150 mL solutions for infusion. The dosage varies based on the type and severity of infection, but a common adult dose is 500 mg once daily or 750 mg once daily for 5–14 days. In patients with reduced kidney function, the dose or dosing interval may need adjustment to prevent drug accumulation.

DRUG INTERACTIONS

Levofloxacin can interact with several medicines. Antacids, iron, calcium, and zinc supplements can reduce its absorption, so they should be taken separately. It may increase the risk of heart rhythm problems when used with other QT-prolonging drugs and can raise bleeding risk with warfarin. NSAIDs may also increase the chance of nervous system side effects like seizures.

FOOD INTERACTIONS

Levofloxacin should not be taken with dairy products (milk, curd) or mineral supplements like calcium, iron, magnesium, zinc, and aluminium, as they reduce its absorption and effectiveness. It should be taken 2 hours before or 4–6 hours after these foods or medicines. It can be taken with or without regular meals.

CONTRAINDICATIONS

Levofloxacin is contraindicated in patients with hypersensitivity to levofloxacin or other fluoroquinolones. It should not be used in children, pregnant, or breastfeeding women unless absolutely necessary. It is also avoided in patients with a history of tendon disorders related to fluoroquinolone use and in those with seizure disorders, as it may increase the risk of tendon rupture and seizures.

SIDE EFFECTS

• Nausea 

• Vomiting 

• Diarrhea 

• Headache 

• Dizziness 

• Abdominal pain 

• Insomnia

OVER DOSE

• Nausea and vomiting 

• Dizziness and confusion 

• Drowsiness or agitation 

• Seizures (serious) 

• Irregular heartbeat (rare)

TOXICITY

Levofloxacin toxicity may affect the nervous system, causing dizziness, confusion, agitation, or seizures. It can also cause gastrointestinal symptoms like nausea and vomiting, and in rare cases lead to heart rhythm problems, tendon damage, kidney or liver dysfunction, and nerve injury (peripheral neuropathy). Severe toxicity is usually linked to overdose or high-risk patients.