Maintenance Dose Calculator
Calculate the steady-state dosage required to maintain target plasma concentrations.
Calculation Result
Required Dose: 0 mg every hours
Maintenance Rate: 0 mg/hr
What is a Maintenance Dose?
A maintenance dose is the amount of drug administered at regular intervals to maintain a specific target concentration of the drug in the patient's plasma at a steady state. In clinical pharmacology, the goal is to balance the rate of drug administration with the rate of drug elimination. When these two rates are equal, the drug has reached a "steady state," ensuring therapeutic efficacy while minimizing the risk of toxicity.
The Maintenance Dose Formula
The core mathematical relationship used in this calculator is based on the principle of clearance. The formula is expressed as:
Maintenance Dose = (Target Cp × CL × τ) / F
- Target Cp: The desired steady-state plasma concentration.
- CL (Clearance): The volume of plasma cleared of the drug per unit of time.
- τ (Dosing Interval): The time between consecutive doses.
- F (Bioavailability): The fraction of the administered dose that reaches the systemic circulation (1.0 for IV, less for oral).
How to Use the Calculator
To use this professional tool, follow these steps:
- Enter the Target Concentration required for the therapeutic effect.
- Input the patient's Clearance rate. This is often calculated based on weight, age, and renal function (like Creatinine Clearance).
- Define the Dosing Interval (how often the medicine is taken).
- Provide the Bioavailability factor. For intravenous medications, enter 1. For oral medications, check the specific drug's pharmacokinetic profile.
- Click "Calculate" to see the required dose per interval.
Frequently Asked Questions
Why is bioavailability important?
Bioavailability accounts for the "first-pass effect" and absorption limitations. If a drug is only 50% absorbed (F=0.5), you must double the oral dose to achieve the same plasma level as an IV administration.
When should maintenance doses be adjusted?
Adjustments are necessary when a patient's clearance changes, commonly due to renal or hepatic impairment. If clearance decreases, the maintenance dose must be lowered to avoid toxic accumulation.