Drug Dosage Calculator

Weight-based dosing is standard for many medications because pharmacokinetic parameters (absorption, distribution, metabolism, excretion) scale with body size. The basic formula is simple: multiply the dose per kilogram by the patient's weight in kilograms. **When weight-based dosing is used**: - **Pediatrics**: Almost all pediatric medications use mg/kg dosing - **Chemotherapy**: Usually uses BSA (mg/m²) but some drugs use mg/kg - **Antibiotics**: Many have weight-based dosing for children and sometimes adults - **Anesthetics**: Induction agents and muscle relaxants are dosed by weight - **Heparin and other anticoagulants**: Weight-based loading and maintenance doses **Important considerations**: 1. **Dose capping**: Many drugs have maximum doses regardless of weight. For example, acetaminophen might be dosed at 15 mg/kg but capped at 1000 mg per dose in adults. 2. **Obese patients**: For some drugs (especially hydrophilic ones), using actual body weight in obese patients can cause overdose. Adjusted or ideal body weight may be more appropriate. 3. **Lean body mass dosing**: For drugs that distribute primarily to lean tissue, dosing by lean body mass is more accurate than total weight. 4. **Round to available strengths**: Calculated doses often don't match commercial formulations. Round to the nearest practical dose (typically within ±10%). **Always verify**: Weight-based dosing doesn't replace clinical judgment. Always check drug references, consider comorbidities, drug interactions, and organ function.