Steady state concentration of a drug is achieved in: September 2007
**Core Concept**
The concept of steady state concentration in pharmacokinetics refers to the point at which the rate of drug administration equals the rate of drug elimination, resulting in a stable plasma concentration of the drug.
**Why the Correct Answer is Right**
At steady state, the amount of drug entering the body equals the amount being eliminated. This occurs after 4 to 5 half-lives of the drug, depending on the drug's pharmacokinetic properties. The liver enzyme cytochrome P450 plays a crucial role in drug metabolism and elimination. In the steady state, the plasma concentration of the drug remains constant, allowing for predictable therapeutic effects and minimizing the risk of toxicity.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because the concept of steady state does not apply to a single dose of a drug. A single dose does not allow for the establishment of a stable plasma concentration.
**Option B:** This option is incorrect because the concept of steady state is not related to the maximum tolerated dose of a drug. The maximum tolerated dose is the highest dose that can be administered without causing significant side effects.
**Option C:** This option is incorrect because the concept of steady state is not related to the duration of action of a drug. The duration of action refers to the length of time a drug remains effective in the body.
**Clinical Pearl / High-Yield Fact**
To achieve steady state, it is essential to administer a drug at a consistent dosing interval, such as every 8 hours, to allow for the establishment of a stable plasma concentration.
**Correct Answer: C. After 4-5 half-lives of the drug.**