MOXIFLOXACIN HYDROCHLORIDE
Clinical safety rating: caution
Animal studies have proved adverse effects but may be safe for humans
Inhibits bacterial DNA gyrase (topoisomerase II) and topoisomerase IV, preventing DNA replication, transcription, repair, and recombination.
| Metabolism | Metabolized primarily via glucuronidation and sulfate conjugation; not significantly metabolized by CYP450 enzymes. A small fraction undergoes N-sulfation or methyl ester formation. |
| Excretion | Approximately 20% of a dose is excreted unchanged in urine, with about 25% recovered as a glucuronide conjugate (M1) and a sulfate conjugate (M2). Biliary/fecal excretion accounts for about 55% of the dose, with a portion undergoing enterohepatic recirculation. |
| Half-life | Terminal elimination half-life is approximately 12-14 hours in healthy adults, allowing once-daily dosing. This is extended in severe renal impairment (creatinine clearance <30 mL/min) and in the elderly. |
| Protein binding | Approximately 45-50% bound to serum proteins, mainly albumin. |
| Volume of Distribution | Volume of distribution is approximately 2.5-3.5 L/kg, indicating extensive tissue penetration, achieving concentrations in tissues such as lung, sinus, and skin that exceed plasma levels. |
| Bioavailability | Oral bioavailability is approximately 90% (range 86-92%), so intravenous and oral doses are equivalent. |
| Onset of Action | For oral administration, plasma concentrations reach therapeutic levels within 1-2 hours. For intravenous infusion, onset is immediate upon reaching steady-state concentrations, typically within the first dose. |
| Duration of Action | With once-daily dosing, plasma concentrations remain above the MIC for most susceptible pathogens for the entire 24-hour interval. The half-life supports a dosing interval of 24 hours. |
| Molecular Weight | 437.89 |
400 mg orally or intravenously once daily for most indications; duration varies by indication.
| Dosage form | SOLUTION/DROPS |
| Renal impairment | No dose adjustment required for mild to moderate renal impairment (CrCl ≥30 mL/min); avoid use in severe renal impairment (CrCl <30 mL/min) due to lack of safety data, though pharmacokinetics are not significantly altered. |
| Liver impairment | No dose adjustment required for mild to moderate hepatic impairment (Child-Pugh A and B); not recommended in severe hepatic impairment (Child-Pugh C) due to lack of data. |
| Pediatric use | Not recommended for use in children <18 years for most indications except for specific conditions like inhalational anthrax (post-exposure) with weight-based dosing: 10 mg/kg orally or intravenously once daily (max 400 mg/day). |
| Geriatric use | No specific dose adjustment required based solely on age; use caution due to increased risk of adverse effects (e.g., QT prolongation, tendinitis, neuropathy) and monitor renal function as elderly patients may have reduced renal clearance. |
| 1st trimester | Avoid use unless no alternative; animal studies show embryotoxicity and teratogenicity at high doses. Human data limited; fluoroquinolones associated with musculoskeletal and neurological risks. |
| 2nd trimester | Avoid use unless no alternative; potential for fetal cartilage damage and arthropathy based on animal models. |
| 3rd trimester | Avoid use unless no alternative; theoretical risk of neonatal joint toxicity and CNS effects. |
Clinical note
Drugs that prolong the QT interval may have additive effects Associated with tendonitis and tendon rupture and may exacerbate myasthenia gravis.
| Placental transfer | Moxifloxacin readily crosses the placenta; fetal concentrations are approximately 50-70% of maternal plasma levels. |
| Breastfeeding | Moxifloxacin is excreted into human breast milk in small amounts. Although the risk to the nursing infant is considered low, the American Academy of Pediatrics recommends caution due to potential for adverse effects on infant gut flora and rare risk of arthropathy. Manufacturer advises discontinuation of nursing or drug based on importance of drug to mother. |
■ FDA Black Box Warning
Fluoroquinolones, including moxifloxacin, are associated with an increased risk of tendinitis and tendon rupture in all ages. This risk is further increased in patients over 60 years of age, those taking corticosteroids, and those with kidney, heart, or lung transplants. Additionally, fluoroquinolones may exacerbate muscle weakness in patients with myasthenia gravis. Avoid use in patients with a known history of myasthenia gravis.
| Common Effects | Eye discomfort Dry eye Burning sensation in eye |
| Serious Effects |
Known hypersensitivity to moxifloxacin or any fluoroquinoloneHistory of tendon disorders related to fluoroquinolone therapyPregnancy (contraindicated in pregnancy according to manufacturer)Lactation (manufacturer advises avoid unless essential)Children and adolescents <18 years of age (due to arthropathy risk)Patients with prolonged QT interval or uncorrected electrolyte disturbances (e.g., hypokalemia, hypomagnesemia), clinically significant bradycardia, or receiving class IA or III antiarrhythmics
| Precautions | Tendon effects: risk of tendinitis and tendon rupture., Myasthenia gravis exacerbation., Peripheral neuropathy: may occur rapidly and be irreversible., Central nervous system effects: dizziness, confusion, seizures, increased intracranial pressure., QT prolongation: avoid in patients with known QT prolongation, electrolyte disturbances, or concurrent use of Class IA/III antiarrhythmics., Hypersensitivity reactions: serious and occasionally fatal anaphylactic reactions., Photosensitivity/phototoxicity., Clostridioides difficile-associated diarrhea., Blood glucose disturbances: both hypoglycemia and hyperglycemia., Avoid in patients with known aortic aneurysm or those at risk., Use with caution in patients with renal impairment (no dose adjustment needed for mild/moderate but caution in severe). |
Loading safety data…
| Lactation Rating | L3 (Moderately Safe) or 'Caution' |
| Teratogenic Risk | Fluoroquinolones like moxifloxacin have been associated with arthropathy in juvenile animals. Human pregnancy data are limited; however, moxifloxacin is generally avoided during pregnancy unless benefit outweighs risk due to concerns about fetal cartilage development. First trimester: no adequate human studies; animal studies show no evidence of teratogenicity but do show fetal toxicity at high doses. Second and third trimesters: potential risk of fetal cartilage damage and arthralgia. The drug crosses the placenta. |
| Fetal Monitoring | Monitor for maternal adverse effects: gastrointestinal disturbances, CNS effects (dizziness, headache), QT prolongation (ECG monitoring if risk factors present), and tendonitis/tendon rupture. Fetal monitoring: consider periodic ultrasound to assess growth if used during second/third trimester, and monitor for signs of neonatal joint issues postpartum. |
| Fertility Effects | Moxifloxacin has not been reported to significantly impair fertility in humans. Animal studies have not shown adverse effects on fertility at clinically relevant doses. |
| Food/Dietary | Avoid taking with dairy products (milk, yogurt), calcium-fortified juices, and antacids or supplements containing magnesium, aluminum, iron, or zinc within 4 hours of moxifloxacin dose as these reduce absorption. Avoid excessive alcohol intake while on this medication. |
| Clinical Pearls | Avoid use in patients under 18 due to cartilage damage risk. Use with caution in elderly or those with known QT prolongation; consider ECG monitoring. Monitor for signs of tendonitis or tendon rupture, especially with concomitant corticosteroids. Adjust dose in severe renal impairment (CrCl <30 mL/min). Moxifloxacin has excellent respiratory and intra-abdominal coverage but limited activity against Pseudomonas aeruginosa. |
| Patient Advice | Take exactly as prescribed; do not skip doses or stop early. · Notify your doctor immediately if you experience tendon pain, swelling, or rupture, especially in the Achilles tendon. · Report any signs of allergic reaction, such as rash, hives, or difficulty breathing. · Avoid prolonged sun exposure and use sunscreen; moxifloxacin increases photosensitivity. · Use caution when driving or operating machinery; may cause dizziness or vision changes. · Take with or without food, but avoid dairy products, calcium-fortified juices, and antacids containing magnesium or aluminum within 4 hours of dose. · Drink plenty of fluids unless otherwise instructed. |