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 principle in proximity to the receptors present in the spinal cord, with which it must interact. to obtain the desired therapeutic action.
Naturally, the intrathecal administration of a drug must be carried out only and exclusively by personnel specialized in this field.
The drugs most commonly administered intrathecally are:
- Local anesthetics (think, for example, of "spinal anesthesia);
- Muscle relaxants;
- 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 known form of intrathecal administration.
In fact, nowadays, the use of intrathecal infusers is also particularly widespread.
Intrathecal infusers - 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 same pump.
The pump is equipped with a reservoir which, when necessary, is refilled by the doctor through an injection carried out at the abdominal level: the needle of the syringe will then reach the pump at its reservoir to allow it to be filled.
The infuser, therefore, has the task of both storing and conveying the drug in the spinal fluid.
Basically, we can distinguish two different types of intrathecal infusoria:
- Continuous infusion intrathecal pumps: as can be understood from the same name, this type of pump allows continuous and constant intrathecal administration of the drug throughout the day;
- Intrathecal pumps with programmed infusion: these infusers - through a regulation carried out with a special external computer - allow the administration of different doses of drug at different times of the day.
Obviously, the insertion of the intrathecal pump and the catheter is carried out with an invasive method through a small surgical intervention. However, the intrathecal administration with the help of infusers of this type is particularly indicated in all those patients who require frequent - and sometimes continuous - drug administration 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, annoying and painful - injections.
Among the different drugs for which it is necessary to resort to intrathecal administration, those most administered through the aforementioned infusors are opioid analgesics used in the treatment of chronic pain and muscle relaxants (such as, for example, baclofen) used in the control of the typical spasticity that occurs. manifests itself in various neurodegenerative diseases, such as, for example, multiple sclerosis.
Intrathecal administration has significant advantages:
- It allows to administer the drug near the site of action on which it has to act;
- Facilitates the passage of the active ingredient through the blood brain barrier (BEE);
- It allows to obtain a more rapid onset of action;
- It allows to administer doses of drug which are much lower than those which must be used in other routes of administration, obtaining in any case the desired therapeutic effect and avoiding the so-called first pass effect;
- Since the intrathecal administration allows to inject smaller doses of the drug, it also allows to decrease the side effects that can occur if the active principle is administered through other routes, enteral or parenteral.
The disadvantages that can arise from intrathecal administration are:
- Pain felt by the patient during the injection;
- Reactions at the injection site;
- Need to contact specialized personnel inside special facilities for the execution of the injection or for the filling of the infuser;
- Possibility of surgical complications when the intervention for the insertion of the intrathecal infuser is performed;
- Difficulty of intervention in case of accidental administration of excessive doses of the drug (a rare event, however, since the intrathecal administration of the drug can only be carried out by specialized personnel).