Understanding Narrow Therapeutic Index (NTI) Drugs and Dosage

Narrow Therapeutic Index Drugs (NTID)

These drugs have a small difference between the minimal therapeutic and minimal toxic concentrations in the blood.

This means that a small increase in the dose can lead to toxic effects, while a small decrease can lead to therapeutic failure.

NTIDs include:

- Warfarin (Coumadin)

- Phenytoin (Dilantin)

- Digoxin (Lanoxin)

Drugs with concentration-dependent toxicity

The toxicity of these drugs increases with their blood concentration, and there is no well-defined therapeutic range.

Examples of such drugs include:

- Aminoglycosides (streptomycin, gentamicin, tobramycin)

- Vancomycin

- Lithium