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. |
| Molecular Weight | 318.3 Da |
| 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 | Avoid during first trimester due to risk of miscarriage and malformations; use only if benefits outweigh risks. |
| 2nd trimester | Use only if clearly needed; monitor fetal growth and well-being. |
| 3rd trimester | Avoid near term due to risk of premature closure of ductus arteriosus and oligohydramnios. |
Clinical note
Comprehensive clinical and safety monograph for LEVOLET (LEVOLET).
| Placental transfer | Crosses placenta; fetal concentrations reach ~50-100% of maternal serum levels. |
| Breastfeeding | Excreted in breast milk in low amounts; use with caution in nursing mothers, especially in preterm infants. |
| Lactation Rating |
■ 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 |
Hypersensitivity to levonorgestrel or any componentKnown or suspected pregnancyUndiagnosed abnormal genital bleeding
| 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. |
| Food/Dietary | High-fiber foods, soy products, grapefruit juice, and walnuts may reduce absorption. Avoid concurrent ingestion; maintain consistent dietary habits. Iron and calcium supplements, as well as antacids containing aluminum or magnesium, should be taken at least 4 hours apart. |
Loading safety data…
| L3 (Moderately Safe) |
| 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. |
| 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. |
| Clinical Pearls | LEVOLET (levothyroxine) absorption is reduced by calcium carbonate, iron, soy, and fiber; take on empty stomach with water 60 minutes before breakfast. For subclinical hypothyroidism, start at 1.6 mcg/kg/day; adjust in 12.5-25 mcg increments every 6-8 weeks. Monitor TSH at 6-8 weeks after any dose change. T4 monotherapy preferred over T3/T4 combinations due to lack of benefit and increased adverse effects. |
| Patient Advice | Take levothyroxine on an empty stomach, at least 60 minutes before breakfast or other medications. · Do not take with calcium supplements, iron supplements, or antacids; separate by at least 4 hours. · Consistency is key: take at the same time every day and use the same brand if possible. · Report symptoms of hyperthyroidism (palpitations, weight loss, heat intolerance) or hypothyroidism (fatigue, weight gain, cold intolerance) to your doctor. · Do not stop or change dose without consulting your healthcare provider; regular blood tests are needed. |