QUIXIN
Clinical safety rating: caution
Comprehensive clinical and safety monograph for QUIXIN (QUIXIN).
Quixin (levofloxacin) is a fluoroquinolone antibiotic that inhibits bacterial DNA gyrase (topoisomerase II) and topoisomerase IV, thereby interfering with DNA replication, transcription, repair, and recombination.
| Metabolism | Levofloxacin is minimally metabolized (approximately 5%) in the liver; the metabolites are desmethyl-levofloxacin and levofloxacin N-oxide. The majority of the drug is excreted unchanged in the urine. |
| Excretion | Renal (approximately 70% unchanged in urine); biliary/fecal (~30%, partly as metabolites and unchanged drug). |
| Half-life | Terminal elimination half-life: 6–8 hours in adults with normal renal function; prolonged in renal impairment (up to 20 hours if CrCl <30 mL/min). |
| Protein binding | ~30% bound, primarily to albumin. |
| Volume of Distribution | 1.5–2.5 L/kg; indicates extensive tissue penetration (e.g., into ocular tissues). |
| Bioavailability | Topical ophthalmic: negligible systemic absorption (<5%). Not available for oral or parenteral use. |
| Onset of Action | Topical ophthalmic: Clinical effect (bacterial growth inhibition) within 30 minutes; maximum bacterial kill within 2 hours. |
| Duration of Action | Topical ophthalmic: Sustained concentrations above MIC for most ocular pathogens for up to 6 hours with a single drop; typical dosing every 6 hours maintains coverage. |
| Molecular Weight | 361.37 |
One to two drops in affected eye(s) every 2 hours while awake, up to 8 times daily for 7-14 days.
| Dosage form | SOLUTION/DROPS |
| Renal impairment | No adjustment required for topical ophthalmic use; systemic absorption minimal. |
| Liver impairment | No adjustment required for topical ophthalmic use. |
| Pediatric use | Children ≥1 year: same as adult dosing; <1 year: safety not established. |
| Geriatric use | No specific dose adjustment; use same as adult dosing. |
| 1st trimester | Avoid use unless benefit outweighs risk; quinolones are associated with arthropathy in juvenile animals, but human data are limited. |
| 2nd trimester | Avoid use unless benefit outweighs risk; potential fetal cartilage damage based on animal studies. |
| 3rd trimester | Avoid use unless benefit outweighs risk; risk of fetal cartilage damage and possible CNS effects. |
Clinical note
Comprehensive clinical and safety monograph for QUIXIN (QUIXIN).
| Placental transfer | Levofloxacin crosses the placenta; detectable in fetal plasma at concentrations approximately 70-80% of maternal levels. |
| Breastfeeding | Quixin (levofloxacin) is excreted into human breast milk in small amounts; caution is advised due to potential adverse effects on infant cartilage development and gastrointestinal flora. Use only if clearly needed and consider monitoring for infant diarrhea or rash. |
■ FDA Black Box Warning
Fluoroquinolones, including levofloxacin, are associated with an increased risk of tendinitis and tendon rupture in all ages. This risk is further increased in older patients (>60 years), patients taking corticosteroids, and patients with kidney, heart, or lung transplants.
| Serious Effects |
History of hypersensitivity to levofloxacin or other quinolonesHistory of tendinitis or tendon rupture with fluoroquinolone useChildren under 18 years (except for specific conditions)Pregnancy (generally avoided)
| Precautions | Fluoroquinolones may exacerbate muscle weakness in patients with myasthenia gravis; avoid use in these patients., Hypersensitivity reactions, including anaphylaxis, can occur after first dose., Prolonged use may result in overgrowth of nonsusceptible organisms including fungi., Avoid contact lens wear during treatment of conjunctivitis., Tendon effects: discontinue at first sign of tendon pain or inflammation. |
| Food/Dietary | No clinically significant food interactions with ophthalmic levofloxacin. Systemic absorption is negligible. |
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| Lactation Rating | L3 (Moderately Safe) |
| Teratogenic Risk | Fluoroquinolones are generally avoided in pregnancy due to arthropathy risk in juvenile animals. Human data are limited but do not show a clear increase in major malformations. First trimester: No established increase in teratogenicity, but reserve for serious infections. Second/third trimester: Potential fetal cartilage damage; avoid unless no alternative. Not recommended in pregnant women due to concerns of fetal musculoskeletal toxicity. |
| Fetal Monitoring | Monitor for maternal adverse effects: tendonitis, QT prolongation (ECG if risk factors), Clostridioides difficile infection. Fetal monitoring: No specific fetal monitoring required, but assess for joint or cartilage damage in neonate if exposure occurs in third trimester. Perform baseline and periodic liver function tests and renal function tests. |
| Fertility Effects | No known adverse effects on human fertility. Animal studies show no impairment of fertility at clinically relevant doses. |
| Clinical Pearls | Quixin (levofloxacin ophthalmic solution) is a fluoroquinolone antibiotic used for bacterial conjunctivitis. It achieves high corneal penetration. Reserve for confirmed bacterial etiology; avoid in viral or fungal infections. Monitor for corneal perforation in patients with corneal epithelial defects or dry eye. Discontinue if rash, urticaria, or other hypersensitivity occurs. |
| Patient Advice | Instill one drop in the affected eye(s) every 2 hours while awake (up to 8 times daily) for the first 2 days, then every 4 hours (up to 4 times daily) for the next 5 days. · Do not wear contact lenses during treatment or while symptoms persist. · Avoid touching the dropper tip to any surface to prevent contamination. · Temporary blurred vision may occur; do not drive or operate machinery until vision clears. · Report worsening symptoms, eye pain, or vision changes immediately. |