Drugs: Routes of Administration
WHAT ARE DRUGS FOR?
Drugs are used in different ways. Some of the major ones are:
- SYMPTOMATIC --To relieve symptoms of diseases. An example of a drug that acts like this is the Aspirin.
- PREVENTIVE -- To prevent getting diseases such as Influenza Flu Virus, Hepatitis, or Chicken Pox. An example of drugs like this is the vaccine, which is usually introduced into a patient's body using an injection.
- DIAGNOSTIC-- Some drugs such as those that has radioactive traces are used for diagnosis purposes. This is visualized under powerful machines that can detect the presence of these minute amounts of radioactivity in the body.
- CURATIVE-- Some drugs like the good ole antibiotics are used to kill the root of the disease such as the bacteria.
- MAINTENANCE-- Some drugs are used to maintain a certain desirable health level. This is useful for weight management issues, heart problems, diabetes, so on.
- CONTRACEPTIVE-- Some drugs are used to prevent fertilization
DRUGS COME IN ALL FORMS
- Some are acidic, basic or neutral
- Some are small or large molecules (such as lipids, carbohydrates, proteins, so on)
- Some are in solid, liquid or gaseous physical state
- Some have localized or generalized site of action
- Some are more soluble than others
- Some may have undesirable effects on the body (specifically in the production of stomach gastric juices)
- Some need to have a very accurate dosage
- Some depends on the health status of the patient (if the patient is constantly vomiting, for example, then oral routes should be avoided)
Since almost all the drugs come in different sizes, shapes, concentration, so on, we need to recognize that almost all drugs are poisonous. Therefore, it is equally vital to know whether a certain concentration is therapeutic or toxic and make sure that we properly administer it.
WHAT MAKES AN IDEAL DRUG?
There are many factors that make an ideal drug. Some of which are:
- FREEDOM FROM DRUG INTERACTIONS
- LOW COST
- CHEMICALLY STABLE
- EASY TO ADMINISTER
Right now, we are looking at the level at which the drug can be administered to the patient's body with ease.
There are many ways in which a drug can be administered. We can divide it into these broad categories:
- ENTERAL (Oral, Sublingual, Rectal)
- PARENTERAL (Intravascular, Intramuscular, Subcutaneous)
- OTHERS (Inhalation, Intranasal, Intraventricular, Topical, Transdermal)
(A) ORAL ROUTE
This is the most used route of administration but is not the best. This particular route requires a very specific pathway from the moment the medicine is popped in the mouth down to the excretion. The metabolic pathway itself is not the same for all drugs; some are absorbed by the gastric walls while some by the intestinal walls. Since a great percentage of it will be excreted out of the body, even before it can enter the bloodstream, then the therapeutic effect will be reduced significantly. Therefore, the bioavailability of the drug through oral route is lessened.
(B) SUBLINGUAL ROUTE
Drugs that are administered via this route are placed under the tongue, where many small blood vessels are located. Also because of the abundance of blood vessels in this region, drugs that are administered via this route are absorbed rapidly. This will allow the drug to enter the bloodstream directly, without passing through the acidic gastric environment or the intestines. One of the major problems with this route is that one has to make sure that the drug is lipid soluble.
(C) RECTAL ROUTE
This is absorbed by veins called external hemorrhoid and since drugs administered through this route do not enter the portal circulation, then a large percentage of the drug will be available in the body (this is because the portal circulation will go through the liver, where come drugs get metabolized).
When the patient is constantly vomiting and cannot hold on food, or if unconscious, this route may be one of the best options. Another scenario could be when the drugs being administered are considered irritants, then rectal route may be used.
Some drugs are incompatible with the gastrointestinal tract so a parenteral route is used. This is especially useful when drug action is needed fast. Since it does not have to go through the digestive tract, there is more control over the drug, and more bioavailability
(A) INTRAVASCULAR/ INTRAVENOUS ROUTE (IV)
Out of the three most common parenteral routes, the IV route is the most used. However, this does not come without any negative effects. Sometimes, because of the very high levels in the bloodstream, there could be adverse reactions. Since the effect is very rapid, it is important to have a controlled amount of drug introduced.
(B) INTRAMUSCULAR ROUTE (IM)
The most common sites of IM administration are the gluteal muscles and the deltoid, where there is a faster rate of absorption compared to the subcutaneous route, but slower rate of absorption compared to the IV route. If the amount of drug (in liquid form) is unusually higher, then this route may be advisable.
(C) SUBCUTANEOUS ROUTE (SC)
This route's rate of absorption is slower than the IV route but faster than the IM route.
This route uses drugs in its gaseous state. By inhaling the drug, it will travel to the lungs where countless of blood vessels are located. The drug easily diffuses into the bloodstream and go to the site of action. This route is almost comparable to the IV route.
(B) INTRANASAL ROUTE
This route may bypass the blood-brain barrier and the rate of absorption is just a tad slower than when administered through an IV route. Since drugs in this route are absorbed by the mucus membrane, it is more easily diffused through the body, compared to oral route. Some of the drugs that are abused are taken through this route.
This route uses creams, gels, tinctures, sprays and other methods in which action is localized. It is usually applied/rubbed on the skin where it gets absorbed. Although its action is localized, it can still get to the bloodstream because of the said absorption.
(D) TRANSDERMAL ROUTE
Usually delivered via a patch which goes through the skin barriers before it enters the bloodstream. This is especially useful when the action desired is maintained for long period (days or weeks). Another form of patch is used to prevent pregnancy (a contraceptive).