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ROUTES OF DRUG ADMINISTRATION

In broad spectrum of Pharmacology we study about how drug interacts with our body and how our body interacts with the drug i.e. the Pharmacokinetics and Pharmacodynamics of drug.

Routes of drug administration simply means as what are they ways to take drug?

If You want to take drugs what can be the factors which may influence are Patients condition, patient’s compliance, emergency and drug related factors. In that most important factor may be feasibility and convenience determine the Routes of administration of Drug.

Choice of Route of Drug Administration depends on:

  1. Physical and chemical properties of the drug.
  2. Site of Action.
  3. Rate and extent of drug absorption.
  4. Onset of action of drug by various routes.
  5. Dose accuracy.
  6. Patient condition.
  7. Patient compliance.
  8. Body’s response.
  9. First pass metabolism of the drug after administration.

What you get below?

  1. Classification
  2. Description of each Route with its sub-types diagrams, etc.
  3. Conclusion
  4. Frequently Asked Questions (FAQs)

Classification

Routes of drug administration classification

If you want classify Routes of drug administration, it may be classified mainly into two types, they are Local route and Systemic route. Further if you want to classify local routes it can be divided into three sub-types, Topical route, deeper route and arterial supply.

Further if you want to classify Systemic route, it can be divided into Oral route, Sublingual route, Rectal route, Cutaneous route, Inhalation route and Nasal route.

Description of each type

LOCAL ROUTES:

Local route of drug administration implies applying drug locally and it produces effect locally at the site of application. Systemic absorption is very less as compared to other routes.

The drug stands locally so the concentration of drug is high at the site of application and it will not expose to rest of the body. As it will not expose to rest of the body, systemic side effect or toxicity is absent or less.

Local route of drug administration is convenient but rapidity of action is very less as compared to systemic route of drug administration.

Topical Route: 

Topical route is a route of Drug Administration, in which the drug is applied externally as topically on skin or mucous membrane for localised action as you apply lotions, creams, pastes, etc. As said mentioned above, it is more convenient as well as encouraging to the patient.

a) Skin: As you apply pastes, ointments, creams, lotions, sprays, and dressing material on the skin, this is a part of topical route.

b) Mucous membrane: The dosage form depends on the site of application-

1. Mouth and pharynxMouth washes, Paints, Gargles, Lozenge
2.Eyes, Ears and NoseDrops, Ointments, Nasal spray
3.Gastrointestinal tractNon-absorbable drugs
4.Respiratory tractInhalational dosage, Aerosols,
5.UrethraJellies
6.VaginaPesseries, Creams, Powders, Vaginal tablets
7.Anal canalOintment, Suppositories
Mucous Membrane

Deeper tissues:

With the help of needles, syringes, injections the deep areas of skin are approachable but the condition is systemic circulation shouldn’t be approached.

Examples of which are Intra-articular injection (hydrocortisone acetate in knee joint), Infiltration around a nerve or intra-thecal injection (lidocaine), retro-bulbar injection (hydrocortisone acetate behind the eyeball).

Arterial supply:

It is a type of local route of drug administration wherein the drug is injected close to arteries.It is used in anticancer drugs, limb malignancy and femoral and brachial artery disease.

Routes of Drug Administration

SYSTEMIC ROUTES:

In this route of drug administration, the administered drug passes in to the blood and from there it is distributed all the body including the site of action. The systemic side effect is present in this route.

The concentration at the site of application or site of administration becomes less progressively. The onset of action is far more as compared to local route. The drug may undergo first pass metabolism.

Systemic routes: a type in routes of drug administration

Oral Route:

Oral route of drug administration is the oldest and is most common mode of drug administration.Among several routes of drug administration the oral route is most basic. This method of drug administration is Safer, convenient, non invasive, generally painless and there is no need of assistance. The dosage form used are Tablets, Solutions, suspensions, Mixtures, Capsules, Elixirs, syrups and many other that can be given orally.

Disadvantages of Oral Route:

1.Tablets, syrups, solution are not in use during emergencies.

2. Onset of action is less.

3. Drugs undergo first pass metabolism so the large part of drug is gets destroy.

4. Unpalatable drugs are difficult to administer. Example is Paraldehyde and chloramphenicol.

5. Patient may feel vomiting (nausea) or may vomit.

6. Drugs may not be absorbed. Example is Streptomycin.

Sublingual (SI) or Buccal Route:

The dosage forms like tablets are kept beneath the tongue or are crushed in the mouth and further it is absorbed sublingually or buccal cavity.

As the Buccal cavity is lipoidal in nature, only lipid soluble drugs absorbes orally. The drugs which are irritating from parental route or mucosal route are administered from sublingual route.

The main and most important advantage is liver is bypassed so that first pass metabolism of the administered drug do not take place. If you notice drug directly get absorbs into systemic circulations and then reaches site of action.

Examples of drugs given sublingually are Nitroglycerine, Soprenaline, Clonidine, Buprenorphine, etc.

Rectal Route:

Rectal drugs are mainly suppositories, enemas, which are inserted rectally.

Rectal Route

The advantage of this is the unpleasant and irritant drugs can be easily given to the patient but the disadvantage is it is inconvenient and embarrassing.

This route of drug administration is frequently used when patient is in unconscious phase and vomits when any oral or sublingual drug is provided. No doubt, absorption is slower may be unpredictable and irregular (exceptions are diazepam solution and paracetamol suppository are Absorbed rapidly within some time in small age). 

Drugs are usually absorbs from external haemorrhoidal veins present in rectal region. Due to this reason the drugs bypass Liver and escapes the First pass metabolism. By frequent use of rectal suppositories and enemas this may lead to inflammation in this region and sores formation can take place.

Examples of some of the drugs administered through rectal route are Indomethacin, Diazepam, Aminophylline, Ergotamine, Paraldehyde and Paracetamol.

Cutaneous Route:

Drugs are applied on the skin it gets absorbed into systemic circulation. As skin is lipoidal in nature, lipid soluble drugs are applied on the skin.

The drug gets absorbed slowly so there is prolonged absorption of drug. Absorption of drug can be enhanced by rubbing the dosage form on the site of application also by using oily base and by an occlusive dressing.

Another advantage of Cutaneous route is liver is bypassed due to which first pass metabolism is not carried out.

Dosage forms like ointments, lotions, pastes, creams, etc are seen.

Transdermal therapeutic system: These are type of cutaneous route wherein the devices in the form of Transdermal adhesive patches are applied over skin. The size of the patches varies from 5 to 20 sq.cm.

This patch contains pockets which has reservoirs of drug that provide constant rate of drug release in the systemic circulation via stratum corneum.

The drug is bound in the reservoir between and occlusive backing film and a rate controlling micropore membrane, the under surface of which contains the drug. The adhesive layer is protected by another film that is to be peeled off just before application.

Here the transport of drug from patch to the skin and then to systemic circulation takes place. The transport is by diffusion technique.

The drug is delivered in such a manner that the rate of drug delivery is slower than rate of drug absorption. The drug delivery is irrespective of site specification. The rate of drug delivery is predictable and constant. Site of application may be mastoid region, chest, abdomen, upper arm, lower back, buttock region.

You can use fentanyl, Nitro glycerin, Nicotine and Estradiol, Isosorbide dinitrate, Hyoscine, and Clonidine as transdermal patches. (Consult doctor before use)

Inhalational route:

Inhalational route is the type of routes of drug administration wherein the drug is administered by means of inhalation. Many volatile liquids and gases are given by inhalational route, so that they reach directly to systemic circulation.

General anesthetics like Ether, Nitrous oxide, amyl nitrile, halothane, etc is to the patient by the route.

As we inhale the drug, it reaches alveoli and bronchial arteries exchange the gases and from there the gas circulates with the help of blood.

If the inhalation is discontinued the drug diffuses back and rapidly is eliminated from exhaled air. This provides controlled administration of drug with proper adjustment.

Ether is less used now a day due to its irritant and inflammation causing effect on bronchial wall and respiratory tract walls and it increases mucous secretion due to which there is difficulty in breathing.

Nasal:

Nasal route of drug administration is wherein the drug is administered with the use of sprays, Aerosols, by which the droplets of the drugs are absorbed by mucous membrane and passes directly in to the systemic circulation. In the is route stomach and liver is bypassed.

Nasal Route

Examples of certain drugs include GnRH agonists, calcitonin and desmopressin

Administered using nasal sprays or by using nebulizers.

Parenteral:

(Par-beyond,  enteral-intestinal.)

Parenteral Routes

Parenteral route of drug administration involves direct injection of drug in to the systemic circulation via injections, syringes.

The bio-availability of drug is 100% because no first pass metabolism is carried out and no drug is lost some were in body, it directly reached into the blood.

In parenteral route the major disadvantage is frequent sterilization is necessary ; this route is bit costlier than any other routes and risky process too.

Various types of Parenteral route are:

  1. Subcutaneous(S.C)
  2. Intramuscular (I.M)
  3. Intravenous(I.V)
  4. Intradermal injections.

Conclusion

Here we have studied many concepts of routes of drug administration with its types, sub-types, advantages, disadvantages, diagrams, tables, etc. Here we have studied many pros and cons of several routes of drug administration.

If you scroll below there are many FAQs on this topic, I hope you will get more clarity of the concept from the answers given below.

Frequently Asked Questions (FAQs):

1) Which route of drug administration is the oldest of all?

Among several routes of drug administration, Oral route of drug administration is the oldest of all.

2) Which route is most economical?

For patient it is Oral as they are cheap.

3) Which route of drug administration has 100% bioavailability?

Parenteral route further more is intravenous route in parenteral route.

4) Which route is most dangerous?

Parenteral route is more risky and dangerous among several routes of drug administration.

5) Why different routes are preferred?

According to bioavailability, emergency an many other factors the route is decided.

6) Which books to refer for routes of administration?

Again same book as in pharmacology, Essentials of medical pharmacology K.D.Tripathi is preferred by many students for studying routes of drug administration.

Grateful to Share My World with You.

Gaurav Gururaj Shanbhag
Grateful to Share My World with You.
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