Routes of drugs administration 

In this blog we explain what is the routes of drugs administration, what are different routes of drugs administration, why route of drugs administration is important and local, internal and systematic route of drug administration .

What is the route of drugs administration?

Most drugs can be administered by a variety of routes. The choice of appropriate route in a given situation depends both on Drug as well as patient related factors.

What are the different routes of drug administration? 

Routes can be broadly divided into those for

a. Local action b. Systemic action 

a. Local routes of drug administration: These routes can only be used for drugs whose systematic absorption from site is minimal or absent. Thus high concentration are attained at the desired site without exposing the rest of the body.

a. The local routes of dug administration are: 

1. Topical: This refers to external applications of the drug to the surface of localized action. Drugs can be effectively delivered to the localized lesions on skin, oropharyngeal / nasal mucosa, eyes, ear canal, anal canal or vegina. 

Ex. Lotion, ointment, cream, powder, rinse, paints, spray, lozenges, suppositories or pessaries.

2. Deeper tissue: certain deep areas can be approached by using a syringe and needle but the drug should be in such a form that systematic absorption is slow.

E.g: intra-articular injection (hydrocortisone acetate in knee joint), infiltration around a nerve or intrathecal injection (lidocaine), retrobulbar injection (hydrocortisone acetate behind the eyeball).

3. Arterial supply: close intra-arterial injection is used for contrast media in angiography; anticancer drug can be infused in femoral or brachial artery to localize the effect for limb malignancies.

b. Systemic routes of drugs administration: 

The drug administered through systematic routes in intended to be absorbed all over, including the site of action, through circulation.

1. Oral: it is ingestion is the oldest and commonest mode of dug administration. it is safer, more convenient does not need assistance, noninvasive often painless, the medicament need not be sterile and so is cheaper, both solid dosage forms (powders, tablets, capsules, spansules, dragees, moulded tablets, gastrointestinal therapeutic system-GITs)  and liquid dosage forms (elixirs, syrups, emulations, mixtures) can be given orally. 

2. Sublingual ( S.I.) or buccal: the tablet or pellet containing the dug is placed under the tongue or crushed in the mouth and spread over the buccal mucosa. only lipid soluble and non-irritating drugs can be so administered. absorption is relatively rapid-action can be produced in minutes. though it is some what inconvenient, one spit the drug after the desired effect has been obtained. the chief advantage is that liver bypassed and drugs with high first pass metabolism can be absorbed directly into systemic circulation. drugs given sublingually are GIN, buprenorphine, desamino-oxytocin.

3. Rectal: certain irritant and unpleasant drugs can be put into rectum as suppositories or retention enema for systemic effect. this route can also be used when the patient is having recurrent vomiting or it unconscious. diazepam, indomethacin, paracetamol, ergotamine and few other drugs ae some times given rectally. 

4. Cutaneous: highly lipid soluble dugs can be applied over the skin for slow and prolonged absorption. the live is also by passed. the dug can be incorporated in an ointment and applied over specified area of skin. absorption of the drug can be enhanced by rubbing the preparation by using an oily base and by an occlusive dressing.

Trans dermal therapeutic system (TTS): this ae devices in the form of adhesive patches of various shapes and sized (5-20 cm2) which deliver the contained drug at a constant rout into systemic circulation via the stratum corneum.

5. Inhalation: volatile liquids and gases are given by inhalation for systemic action.

e.g. general an anesthetics, absorption take place from the vast surface of alveoli-action is very rapid.

6. Nasal: the mucous membrane of nose can readily absorb many drugs, digestive juices and liver are bypassed. however only certain drugs like GnRH agonists calcitonin and desmopressin applied as a spray or nebulized solution nave been used by this route.

7. Parenteral: (par-beyond, enteral-intestinal) conventionally, parenteral refers to administration by injection which takes the drug directly into by injection which takes the drug directly into by the drug directly  into by the tissue fluid or blood without having to cross the enteral mucosa.  the limitation of oral administration are circumvented.