What is the typical dosing regimen and potential side effects of Oxandrolone (Anovar)?

Oxandrolone Dosing and Side Effects

Dosing Regimens

For adults, the FDA-approved dosing of oxandrolone ranges from 2.5 mg to 20 mg daily, divided into 2 to 4 doses, with therapy typically lasting 2 to 4 weeks and repeated intermittently as needed. 1

Adult Dosing

• Standard range: 2.5-20 mg daily in divided doses 1
• Minimum effective dose: As low as 2.5 mg daily may provide benefit 1
• Typical duration: 2-4 weeks per course, repeated intermittently 1
• Geriatric patients: 5 mg twice daily (10 mg total daily) is recommended due to greater sensitivity to fluid retention and hepatic transaminase elevations 1

Pediatric Dosing

• Maximum dose: ≤0.1 mg/kg body weight daily (or ≤0.045 mg/lb) 1
• Administration: Intermittent courses as indicated 1
• Monitoring requirement: X-ray examinations every 6 months to assess bone age and epiphyseal maturation 1

Context-Specific Dosing from Clinical Literature

For hereditary angioedema prophylaxis (off-label use documented in guidelines):

• Adult dose: 10 mg/day (range 2.5 mg every 3 days to 20 mg/day) 2
• Pediatric dose: 0.1 mg/kg/day (range 2.5 mg/week to 7.5 mg/day) 2

Side Effects

Common Side Effects

The most frequently documented adverse effects include virilization in women, transient hepatic transaminase elevations, and lipid profile alterations. 1, 3

Androgenic/Virilizing Effects

• In women: Voice deepening, hirsutism, acne, clitoromegaly, menstrual irregularities 1
• Critical warning: Discontinue immediately at first sign of mild virilization to prevent irreversible changes 1
• In males: Excessive or persistent erections, acne aggravation 1

Hepatic Effects

• Transient transaminase elevations: Most common hepatic effect 3
• Serious hepatotoxicity: Unlike other C17-alpha-alkylated steroids, oxandrolone does NOT typically cause jaundice, cholestatic hepatitis, peliosis hepatis, or hepatic neoplasms 3
• Monitoring: Liver function tests should be obtained periodically 1

Lipid Alterations

• HDL cholesterol: Decreased 1
• LDL cholesterol: Increased 1
• Clinical implication: Requires caution in patients with cardiovascular disease history or risk 1
• Monitoring: Serum lipid levels should be checked periodically 1

Uncommon but Serious Side Effects

Hematologic

• Coagulation factors: Suppression of factors II, V, VII, and X with increased prothrombin time 1
• Polycythemia: Monitor hemoglobin and hematocrit with high doses 1

Endocrine/Reproductive

• Reproductive suppression in males: Testicular weight reduction, decreased spermatogenesis, suppressed FSH and LH 1, 4
• Pediatric growth effects: Accelerated epiphyseal maturation that may continue 6 months post-discontinuation, potentially compromising adult height 1, 5

Fluid Retention

• Edema: Particularly in elderly patients and women 1
• Increased risk: When combined with adrenal corticosteroids or ACTH 1

Gastrointestinal

• Symptoms: Nausea, vomiting 1

Long-Term/Rare Complications

• Prostatic effects: Increased risk of prostatic hypertrophy and carcinoma in geriatric males 1
• Hepatic tumors: Reported with long-term, high-dose therapy (though less common with oxandrolone than other C17-alkylated steroids) 1

Critical Drug Interactions

Warfarin (Most Clinically Significant)

Oxandrolone causes a 5.5-fold decrease in required warfarin dose (approximately 80-85% reduction) to maintain therapeutic INR. 1

• Mechanism: Increases S-warfarin half-life from 26 to 48 hours 1
• Clinical manifestations: Microscopic hematuria (60% of patients), gingival bleeding 1
• Management: Close INR/PT monitoring required when initiating, adjusting, or discontinuing oxandrolone; monitor for occult bleeding 1

Oral Hypoglycemic Agents

• Effect: May inhibit metabolism of oral hypoglycemics 1
• Management: Monitor blood glucose closely 1

Monitoring Requirements

Baseline and Periodic Assessments

• Hepatic: Liver function tests periodically 1
• Lipids: Serum lipid levels periodically 1
• Hematologic: Hemoglobin and hematocrit with high doses 1
• Pediatric bone age: X-ray every 6 months during treatment 1
• Calcium levels: Frequent monitoring in women with disseminated breast carcinoma 1

Clinical Monitoring

• Women: Observe for virilization signs (voice changes, hirsutism, acne, clitoral enlargement) 1
• All patients: Nausea, vomiting, skin color changes, ankle swelling 1
• Males: Excessive/persistent erections 1

Special Populations and Contraindications

Absolute Contraindications

• Pregnancy: Category X - causes masculinization of female fetus 1
• Breast carcinoma in males 1
• Known or suspected prostate carcinoma 1
• Nephrosis or nephrotic phase of nephritis 1
• Hypercalcemia 1

Relative Contraindications/Cautions

• Pediatric use: Only by specialists aware of bone maturation effects; risk of compromising adult height 1, 5
• Geriatric males: Increased risk of prostatic complications 1
• Cardiovascular disease: Caution due to lipid effects 1
• Nursing mothers: Unknown if excreted in breast milk; consider discontinuing nursing or drug 1