Aerosol medications are used commonly in mechanically ventilated patients. Several classes of drugs with different properties and indications may be given by inhalation. In all cases, inhaled therapy's main advantage over the systemic route is that, for a given therapeutic response, the drug dose is several-fold lower, whereas systemic absorption is negligible. Because of this, the side effects are minimized greatly. Additionally, for some medications, the systemic route either causes nonacceptable side effects or results in considerably inferior therapeutic response, rendering the inhaled route the method of choice of drug administration. Bronchodilators, vasoactive drugs, surfactant, antibiotics, and helium are some agents that can be inhaled during mechanical ventilation.