What does an increased therapeutic index indicate?

An increased therapeutic index signifies that there is a larger margin between the effective dose of a drug and its toxic dose. This means that the drug can be administered at therapeutic levels without approaching toxicity. A higher therapeutic index indicates greater safety in drug administration because it allows a larger window of dosage within which the drug can be effective without causing harmful effects.

In contrast, a lower therapeutic index suggests a higher risk of toxicity, as the effective dose is closer to the toxic dose. This concept is particularly important in clinical practice, as it helps healthcare providers select medications that are safer for patients, especially those who may require long-term treatment or have multiple health issues.

The other options do not directly correlate with the concept of therapeutic index. While a drug with a high therapeutic index may also have efficacy, safety is the primary concern that the therapeutic index addresses. Dependency on the drug and duration of action are related to different pharmacological properties and are not determined by the therapeutic index alone.