LEVOLET
Clinical safety rating: caution
Comprehensive clinical and safety monograph for LEVOLET (LEVOLET).
Levolet (levothyroxine) is a synthetic thyroid hormone that replaces endogenous thyroxine (T4). It is converted to triiodothyronine (T3) in peripheral tissues, which binds to thyroid hormone receptors to regulate gene expression, increasing metabolic rate and protein synthesis.
| Metabolism | Hepatic metabolism via deiodination (D1, D2, D3 isoenzymes) and glucuronidation; approximately 80% of absorbed T4 is converted to T3. Also metabolism via sulfation and biliary excretion. |
| Excretion | Renal: 70-80% unchanged, biliary/fecal: 20-30% as metabolites. |
| Half-life | Terminal elimination half-life: 6-8 hours; shorter in patients with hepatic impairment. |
| Protein binding | 70-80% bound to albumin. |
| Volume of Distribution | 0.6-1.0 L/kg, indicating extensive tissue distribution. |
| Bioavailability | Oral: 70-80%; intravenous: 100% (bioavailability by definition). |
| Onset of Action | Oral: 30-60 minutes; intravenous: 5-10 minutes. |
| Duration of Action | Oral: 8-12 hours; intravenous: 6-8 hours; extended release: up to 24 hours. |
| Action Class | Quinolones/ Fluroquinolones |
| Brand Substitutes | Cenquin 500mg Tablet, Levocef 500mg Tablet, Levoshan 500mg Tablet, Qulef 500mg Tablet, Levolve 500mg Tablet, Levonac 750mg Tablet, Q Life 750mg Tablet, Veloxin 750mg Tablet, Ultramycin 750mg Tablet, Uribact 750mg Tablet |
Levofloxacin 500 mg orally or intravenously once daily for 5-14 days depending on indication.
| Dosage form | TABLET |
| Renal impairment | CrCl 20-49 mL/min: 500 mg loading dose, then 250 mg every 24 hours; CrCl 10-19 mL/min: 500 mg loading dose, then 250 mg every 48 hours; CrCl <10 mL/min on dialysis: 500 mg loading dose, then 250 mg every 48 hours. |
| Liver impairment | No dosage adjustment required for mild to moderate hepatic impairment (Child-Pugh A or B). Not studied in severe hepatic impairment (Child-Pugh C); use with caution. |
| Pediatric use | Not recommended for use in pediatric patients due to potential musculoskeletal toxicity. For inhalational anthrax: ≥50 kg: 500 mg IV/orally every 24 hours; <50 kg and ≥6 months: 8 mg/kg IV/orally every 12 hours (max 250 mg/dose); <6 months: 8 mg/kg IV/orally every 12 hours (max 250 mg/dose). |
| Geriatric use | Use lower doses based on renal function. Increased risk of tendinitis and tendon rupture. Monitor renal function and QT interval. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for LEVOLET (LEVOLET).
| Breastfeeding | Levofloxacin is excreted into human breast milk. The milk-to-plasma (M/P) ratio is approximately 0.8–1.0. The dose received by the infant is estimated to be 2-7% of the maternal weight-adjusted dose, which is generally considered low. However, due to potential adverse effects (e.g., arthropathy, gastrointestinal disturbance), caution is advised. Alternative antibiotics are preferred during breastfeeding, especially for young infants. The manufacturer recommends caution and weighing risk versus benefit. |
| Teratogenic Risk | Levofloxacin (Levolet) is a fluoroquinolone antibiotic. Animal studies have shown fetal toxicity (e.g., skeletal abnormalities, weight loss) at maternal doses. Human data are limited but suggest an increased risk of tendon damage and possibly neurodevelopmental effects in offspring. However, the direct teratogenic risk is considered low based on population studies. Use is generally avoided during pregnancy, especially in the first trimester, unless no safer alternatives exist. Third-trimester use may carry risk of neonatal joint/tendon abnormalities. |
■ FDA Black Box Warning
Not approved for weight loss or obesity; serious cardiovascular toxicity or death may occur, especially at high doses. Contraindicated in thyrotoxicosis and uncorrected adrenal insufficiency.
| Serious Effects |
Untreated thyrotoxicosis (e.g., Graves disease), uncorrected adrenal insufficiency, recent myocardial infarction (relative), hypersensitivity to levothyroxine or excipients.
| Precautions | Cardiovascular risk: can exacerbate angina, arrhythmias, or heart failure, especially in elderly. Monitor thyroid function tests; adjust dose in adrenal insufficiency (use corticosteroids first). Osteoporosis risk with TSH suppression over long term. Rapid dose increase may precipitate thyrotoxic crisis. |
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| Fetal Monitoring | Monitor for maternal adverse effects: tendonitis/tendon rupture, neurotoxicity (dizziness, seizures), QT prolongation (ECG monitoring if risk factors), and hypoglycemia. Fetal/neonatal monitoring: no specific mandated monitoring, but if used late in pregnancy, observe neonate for signs of joint or tendon issues. Baseline renal function and liver function tests recommended due to hepatic/renal excretion. |
| Fertility Effects | No evidence of direct negative effects on fertility in humans. Animal studies have not shown impaired fertility. However, as with any severe infection, temporary reduction in fertility may occur due to illness-related stress. |