Generality
The intrathecal route of administration is a particular type of parenteral administration, which consists in injecting the drug directly into the spinal fluid. In this way, it is possible to administer the desired active ingredient near the receptors present at the spinal level, with which it must interact to obtain the desired therapeutic action.
The drugs most commonly administered intrathecally are:
- Local anesthetics (think, for example, of spinal anesthesia);
- muscle relaxants;
- anticancer;
- Opioid analgesics.
Types of Intrathecal Administration
As mentioned, intrathecal administration involves injecting the drug directly into the spinal fluid. However, direct injection is not the only form of intrathecal administration known.
In fact, nowadays, the use of intrathecal infusoria is particularly widespread.
Intrathecal infusori - also known as intrathecal pumps - are special medical devices that allow the drug to be administered in small doses continuously, or at regular intervals, depending on the case.
The intrathecal pump is usually placed under the skin in the abdominal area. The drug then reaches the spinal fluid through a small catheter, which is positioned at the spinal level and which is in communication with the pump itself.
The pump is equipped with a tank which, when necessary, is supplied by the doctor via an abdominal injection: the needle of the syringe will then reach the pump at its reservoir to allow filling.
Therefore, the infuser has the task of storing and conveying the drug in the spinal fluid.
Basically, we can distinguish two different types of intrathecal infusori:
- Intratecal pumps with continuous infusion : as can be understood from the same name, this type of pump allows a continuous and constant intrathecal administration of the drug during the day;
- Intratecal pumps with programmed infusion : these infusors - through an adjustment carried out with a special external computer - allow the administration of different doses of medication at different times of the day.
Obviously, the insertion of the intratecal pump and the catheter is carried out with an invasive method through a small surgical intervention. However, intrathecal administration with the aid of infusori of this type is particularly indicated in all those patients who need frequent - and sometimes continuous - drug administrations in order to control the symptoms of the pathology they suffer from. The insertion of the intrathecal infuser, in fact, allows the patient not to be subjected to continuous - and, in the long run, bothersome and painful - injections.
Among the different drugs for which it is necessary to resort to intrathecal administration, those most commonly administered through the aforementioned infusori are opioid analgesics used in the treatment of chronic pain and muscle relaxants (such as, for example, baclofen) used in the control of typical spasticity manifested in various neurodegenerative diseases, such as, for example, multiple sclerosis.
Advantages
Intrathecal administration has considerable advantages:
- It allows to administer the drug near the site of action on which it must act;
- Facilitates the passage of the active ingredient through the blood-brain barrier (BEE);
- It allows for a more rapid onset of action;
- It allows to administer much lower drug doses than those that must be used in other routes of administration, however obtaining the desired therapeutic effect and avoiding the so-called first pass effect;
- Since the intrathecal administration allows the injection of smaller doses of drug, it also allows to reduce the side effects that can occur if the active ingredient is administered through other enteral or parenteral routes.
Disadvantages
The disadvantages that can result from intrathecal administration are:
- Pain perceived by the patient during the injection;
- Reactions at the injection site;
- Need to contact specialized personnel in special facilities to perform the injection or to fill the infuser;
- Possibility of surgical complications when the surgery is performed to insert the intrathecal infuser;
- Difficulty in intervening in case of accidental administration of excessive doses of drug (a rare event, since the intrathecal administration of the medicine can only be performed by specialized personnel).
