Routes of administration of a drug

The choice of a route of administration is very important, because it can influence the whole pharmacokinetic process of the molecule introduced into our body.

The choice on how to administer a drug depends mainly on the target to be hit with that particular active ingredient; for example, in the presence of a cutaneous mycosis or an allergic form of the skin the transcutaneous route of administration will be chosen.

Furthermore it must be taken into account:

• of the pharmaceutical form;
• of the rapidity in reaching a certain effect (for example during an emergency treatment, such as anaphylactic shock, a route of administration is used which allows an immediate achievement of a certain effect);
• of the duration of the effect and finally of the patient's health conditions.

The main routes of administration are:

• Enteral routes of administration (oral, sublingual, rectal)
• Parenteral routes of administration (intravascular, intramuscular, subcutaneous, intradermal)
• Route of inhaled administration
• Transcutaneous route of administration

There are also other routes of administration such as intradermal, intrathecal, intra-articular, intra-cavitary, intra-arterial and transmuscular.

The intradermal route of administration is used for allergy testing and the maximum injectable volume is 0.1 - 0.2 ml.

The intra-arterial route of administration is applied in particular cases, such as when high concentrations of drug are to be obtained in certain organs (eg angiographies).

The intrathecal route of administration involves injecting the active ingredient directly into the CSF flowing into the cerebral ventricles and surrounding the spinal cord. The drug administered easily exceeds the BEE (Blood-brain barrier). This route is widely used in surgical operations that require local anesthesia (spinal or epidural anesthesia).