What is the appropriate dosing for medications?

Appropriate Medication Dosing Guidelines

Medication dosing must be tailored to specific patient characteristics including age, weight, renal function, and hepatic function to optimize efficacy while minimizing toxicity. The most recent and highest quality evidence provides clear dosing recommendations for various medication classes and patient populations.

General Dosing Principles

Age-Based Dosing Considerations

Adults

• Standard adult dosing typically applies to individuals ≥15 years of age 1
• For adults >59 years: Reduce doses of certain medications (e.g., aminoglycosides) to 10 mg/kg/day (750 mg maximum) 1

Children

• For most medications, pediatric dosing should be based on:
  • Weight-based dosing for children <2 years old
  • Body surface area (BSA) for children >6 months when appropriate 2
• Specific age-based recommendations:
  • Neonates/infants <1 year: Many medications lack safety data; use with extreme caution
  • Children 1-9 years: Often require higher mg/kg doses than adults due to faster metabolism
  • Children ≥10 years: May use adult dosing if weight >40 kg for many medications 1

Organ Function-Based Dosing

Renal Impairment

• Dose adjustment required for medications with renal clearance
• Base adjustments on creatinine clearance (CrCl):
  • CrCl <50 mL/min: Reduce dose or extend dosing interval for drugs like amantadine 1
  • CrCl <10 mL/min: Further reduction required for drugs like rimantadine (100 mg/day) 1
• For dialysis patients: Administer after dialysis to avoid premature drug removal 1

Hepatic Impairment

• For high hepatic extraction drugs: Reduce both initial and maintenance doses
• For low hepatic extraction drugs: Maintain initial dose but reduce maintenance dose
• For drugs with biliary elimination: Monitor closely in cholestatic disease 3

Specific Medication Class Dosing

Antiviral Medications

Influenza Antivirals

• Oseltamivir (adults): 75 mg twice daily for treatment; 75 mg once daily for prophylaxis 1
• Oseltamivir (children): Weight-based dosing
  • <15 kg: 30 mg twice daily
  • 15-23 kg: 45 mg twice daily
  • 23-40 kg: 60 mg twice daily

  • 40 kg: 75 mg twice daily 1

• Zanamivir (≥7 years): 10 mg (two 5-mg inhalations) twice daily 1

Pain Medications for Neuropathic Pain

Tricyclic Antidepressants

• Start with 25 mg at bedtime
• Increase by 25 mg every 3-7 days as tolerated
• Maximum: 150 mg/day
• Trial duration: 6-8 weeks with at least 2 weeks at maximum tolerated dose 1

Anticonvulsants

• Gabapentin:
  • Starting dose: 100-300 mg at bedtime or 100-300 mg three times daily
  • Titration: Increase by 100-300 mg every 1-7 days as tolerated
  • Maximum: 3600 mg/day in 3 divided doses
  • Trial duration: 3-8 weeks for titration plus 2 weeks at maximum dose 1
• Pregabalin:
  • Starting dose: 50 mg three times daily or 75 mg twice daily
  • Titration: Increase to 300 mg/day after 3-7 days, then by 150 mg/day every 3-7 days
  • Maximum: 600 mg/day (200 mg three times daily or 300 mg twice daily)
  • Trial duration: 4 weeks 1

Antipsychotics for Alzheimer's Disease

Atypical Antipsychotics

• Risperidone: Start 0.25 mg/day at bedtime; maximum 2-3 mg/day in divided doses
• Olanzapine: Start 2.5 mg/day at bedtime; maximum 10 mg/day in divided doses
• Quetiapine: Start 12.5 mg twice daily; maximum 200 mg twice daily 1

Special Considerations

Renal Replacement Therapy

• Peritoneal dialysis: Generally requires less dose adjustment than hemodialysis
• For CAPD patients with residual renal function: Dosing similar to pre-end-stage renal disease
• For anuric CAPD patients: Reduce doses further 4

Common Pitfalls to Avoid

1. "Small adult" dosing for children: Children are not simply small adults; they have unique pharmacokinetic parameters requiring specific dosing approaches 5
2. Ignoring renal function in elderly: Elderly patients often have decreased renal function despite normal serum creatinine levels 3
3. Failure to adjust for organ maturation: In children <2 months, hepatic metabolism is significantly reduced; use extreme caution with hepatically metabolized drugs 2
4. Overlooking drug interactions: Consider potential interactions that may alter drug metabolism or clearance
5. Not accounting for protein binding changes: In renal dysfunction, reduced protein binding can increase free drug concentration and toxicity 6

When dosing medications, always consider the patient's specific characteristics and monitor closely for efficacy and adverse effects, particularly when using medications with narrow therapeutic indices.