Routes of Drug Administration

If you require medication, for whatever ailment, when taking a medication due to whatever aliment, the drug administration can vary depending on various circumstances, for example, the desired effect of the medication, whether the medication is intended to be local (aimed at a specific areaof the body) or systemic (aimed at the whole body), as well as the patient's well-being. A list of commonly used routes of drug administration can be found below, along with useful information about dosage and abbreviations.

Routes of Drug Administration

1. Enteral—Entering Intestinal/Digestive Tract


The mouth route is the most commonly used route of drug administration due to the ease in which the drugs can be taken. This method also provides the most difficult pathway for the drug to reach the targeted area. Drugs which are taken orally have a high chance of incurring the first-pass effect—also known as first-pass metabolism, which refers to the drug concentration being reduced before arriving at the systemic circulation.


Rectal administration can deliver both systemic and local effects, although it has proven to be rather ineffective at times. This type of administration can be useful for those who find it difficult to swallow, or keep down medication, for example, people with vomiting condition.


Although this type of administration does not lead to the drug entering the gastrointestinal tract, it is placed under the tongue, therefore, it is considered oral and enteral. The medication rapidly diffuses into the network of capillaries, directly entering the system circulation.

2. Parenteral—Medication That Avoids the Gastrointestinal Tract

Intravenous (IV)

This is the most common parenteral route of drug administration, which is often administered when a quick effect is required from the drug. This method involves injecting the medication straight into systemic circulation. However, there are numerous drawbacks to this method, including giving too high a concentration of the medication.

Intramuscular (IM)

This method of drug administration offers patients with a faster effect than medication that is taken orally. Through this route, the drug can be in aqueous or depot form. But the aqueous can be absorbed faster than depot form. Besides, the amount and rate of absorption are highly dependent on local blood flow and where the injection is made.

Subcutaneous (SC)

Much like IM injections, SC injections need similar absorption. This route of drug administration is slower to take effect than IV, but also has reduced risks.

3. Other Routes

  • Inhalation: This route is typically used for drugs that are gaseous, or for medications that can be given in aerosol, such as an asthma pump. This form of administration offers almost instantaneous effects.
  • Intranasal: This is the term given to medications that are administered through the nose.
  • TopicalMedication that is supplied exactly when and where it is required or desired.
  • TransdermalThis is the term given to medication that is absorbed through the skin, the rate of absorption, however, is dependent upon an individual's skin characteristics.
  • Intrathecal/Intravetricular: For this route, the medication is administered into cerebrospinal fluid.

Drug Administration on Dosage and Time


To correctly determine how much of a medication you should be taken, you should always seek advice from a medical professional. Although most medications advise the recommended dosage within the instructions, you should still have a consultation with your doctor before proceeding. It can be very difficult to determine the correct dosage of medication when treating many illnesses and many factors can affect your required dosagesuch as your age and physical state, etc.


It is also important to know when to take the medication. Many types of treatments require the medication to be taken consistently at precises times, or with precise intervals between each dosage. If these strict guidelines are not followed, then the treatment may prove to be ineffective.

Below is a table with some common abbreviations used with prescriptions and medication:

Abbreviation in Prescriptions



Taken by mouth


Taken after meals


Taken before meals


Taken twice daily


Taken three times a day


Taken four times a day


Taken every other day


Taken in the morning


Taken every four hours


Taken at bedtime

ad lib.

Taken as desired


Taken as needed



Pros & Cons of Different Routes of Drug Administration

1. Oral

Pros: Easily administered; preferable to patients; slow-release medications may extend the duration of the effect; medications are formulated to avoid stomach acids and digestive enzymes.

Cons: Unsuitable for those who are experiencing severe vomiting or have difficultyswallowing. Also, because it is absorbed slowly, this route is not fast acting. And unpredictable effect due to stomach acids and digestive enzymes should be noticed.

2. Rectal

Pros: Absorption rate is good as the haemorrhoidal veins connect and drain straight into the inferior vena cava.

Cons: Disliked by some patients; not suitable for those who have undergone anal or rectal surgery/injury.

3. Subcutaneous or Intramuscular

Pros: Absorption is good; effect of medication happens quicker than many other routes of drug administration; can have extended duration of medicinal effect, depending on formulation.

Cons: Absorption can be unpredictable; injections may hurt or scare patients (especially children).

4. Intravenous

Pros: Offers a very dependable effect, drugs reaches the systemic circulation instantaneously.

Cons: Requires specialist equipment; requires more work from health care professionals than other routes; can be unnerving to some patients; disposed to t infection; may cause adverse reactions.

5. Topical

Pros: Easy to administer; extremely un-invasive; high rate of patient satisfaction.

Cons: Very slow rate of absorption.

6. Inhaled

Pros: Extremely high rate of absorption.

Cons: Effectiveness depends upon the patient's inhaler, and their technique when using it.

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