*4.4.2. Intramuscular injection*

This method of drug delivery ensures rapid absorption of the drug in aqueous solutions. Slow and even absorption is possible when drugs are suspended in oily vehicles.

#### *4.4.3. Intravenous administration*

This route ensures rapid delivery of the desired blood concentration of the drug to be obtained accurately and immediately and is the preferred route of delivery in emergency situations. Irritating drugs are delivered intravenously because the veins have low sensitivity to pain. This mode of delivery is also preferred for drug such as the barbiturates and phenytoin, antiseizure drugs which dissolve only in rather strong alkaline solution and therefore need the blood to buffer the pH of the drug solution for better solubility. Drugs such as ethylene diamine tetra acetic acid (EDTA) for treatment of heavy-metal poisoning are given by intrave‐ nous injection or through an infusion because they are poorly absorbed in the gut. The other advantage of this mode of delivery is the avoidance of the hepatic and pulmonary first-pass effect. Generally, the properties of the drug may determine the route that must be used for reasonable efficacy.
