sources & Routes of drug administration

Routes of Drug Administration: 

Routes of Drug Administration Dr Rakesh Mittal Asst. Professor

PowerPoint Presentation: 

Local routes Systemic routes Enteral Parenteral

Local routes : 

Local routes Used for localised lesions at accessible sites. Systemic absorption of drug is minimal. High concentration are attained at desired site Systemic side effects/toxicity are minimal

1. Topical : 

1. Topical External application of drug to the surface for localised action Convenient a) Skin – ointments, cream, lotion, paste, powder, dressing, spray etc

PowerPoint Presentation: 

b) Mucous membrane: Mouth & pharynx – paints, lozenges, mouth washes Ears, eyes, nose – drops, nasal sprays etc Bronchi & lungs – inhalational, aerosols Urethra – jellys , irritating solutions Vagina – pesseries, vaginal tab, douches Anal canal – suppositories, ointment

2. Deeper tissues : 

2. Deeper tissues Approached by using syringe & needle. Systemic absorption will be slow Eg . Intra- articular injection – hydrocortisone ac. Intrathecal injection – lignocain, amphotricin Retrobulbar injection - hydrocortisone ac.

3. Arterial supply : 

3. Arterial supply Closed intra-arterial injections – contrast media in angiography. Anticancer drug can be infused – femoral / brachial artery for limb malignancy

Systemic routes.. : 

Systemic routes.. Drugs administered through this route is intended to be into blood & distributed all over. Oral Sublingual Rectal Cutaneous Inhalational Nasal Parentral

1. Oral route : 

1. Oral route Oldest & commonest mode Advantages Safer Convenient - easy to take Self- administered Non invasive - pain free Need not be sterile – Cheap Solid forms – powder, capsules, spansules , etc Liquid – syrups, emulsions, mixtures

Oral route- Disadvantages : 

Oral route- Disadvantages Some drug may be not be absorbed (streptomycin) First-pass effect - drugs absorbed orally are initially transported to the liver via the portal vein Irritation to gastric mucosa - nausea and vomiting Destruction of drugs by gastric acid and digestive juices. (insulin, penicillin G) Effect too slow for emergencies Unpleasant taste of some drugs (paraldehyde) Difficult in uncooperative/ unconscious patient

First Pass metabolism: 

First Pass metabolism

2. Sublingual : 

2. Sublingual Some drugs are taken as smaller tablets which are held under the tongue/ crushed in the mouth and spread over buccal mucosa. Only lipid soluble & non irritating Advantages rapid absorption drug stability avoid first-pass effect Spit after the desired effect is obtained

PowerPoint Presentation: 

Disadvantages inconvenient unpleasant taste of some drugs Examples : Nitroglycerine Isoprenaline Nifedipin Clonidine Methyltestosterone

3. Rectal : 

3. Rectal Certain irritant & unpleasant drug unconscious patients and children If patient is having nausea or vomiting Drug absorbed into external haemorrhidal vein Good for drugs affecting the bowel – laxatives Examples : Aminophyllin, indomethacin, paraldehyde, diazepam

PowerPoint Presentation: 

Disadvantages: Inconvenient & embarrassing Easy to terminate exposure Absorption is slow, irregular, variable Rectal inflammation can occur form irritant drug

4. Cutaneous : 

4. Cutaneous Highly lipid soluble drugs are applied over the skin for slow & prolonged absorption. Liver is bypassed Drugs can be incorporated in an ointment & applied over specified area of skin. TTD (Transdermal Therapeutic system) Adhesive patches – deliver drugs at constant rate through statum corneum. Nitroglycerine, fentanyl, nicotine, estradiol

5. Inhalational : 

5. Inhalational Volatile liquids & gases eg. General anaesthetics , a mylnitrate. Absorption takes place form surface of alveoli – action is rapid Controlled administration is possible with adjustments. Irritant vapours (ether) causes inflammation of respiratory tract & increases secretion.

6. Nasal : 

6. Nasal Mucous membrane of nose can readily absorb many drugs. Digestive juices & liver are bypassed Example - GnRH agonist , desmopressin , insulin

7. Parentral (beyond intestine): 

7. Parentral (beyond intestine) Administered by injections – directly into the tissue fluid / blood. Limitations of oral are circumvented Action is faster & surer (emergency) Employed in unconscious/vomiting patient Liver is bypassed No chance of interference by food/ digestive juices

Disadvantages : 

Disadvantages Sterilized & costlier Invasive & painful Assistance required Local tissue injury More risky – no withdrawal back of given dose

a.. Subcutaneous : 

a.. Subcutaneous Drug deposited in the loose subcutaneous tissue richly supplied by nerves Less vascular supply- slow absorption Self injection is possible as deep injection not required Avoided in shock – absorption is delayed Repository preparation – oily /aqueous is given

Special forms of s.c.: 

Special forms of s.c . Dermojet – needle is not used High velocity jet of drug solution is projected from a microfine orifice . Solution passes through the superficial layer and gets deposited in subcutaneous tissue. Painless & suited for mass inoculation.

PowerPoint Presentation: 

ii) Pellet implantation – Drugs as solid pellet is introduced with a trochar and cannula. Sustained release of drugs over weeks Testosterone & DOCA

PowerPoint Presentation: 

iii) Sialistic & biodegradable implant – Crystalline drug is packed in tubes made of suitable materials & implanted under skin Slow & uniform leaching of drugs occur over months providing constant blood level Non biodegradable implant have to removed Example – norplant

b…Intramuscular : 

b…Intramuscular Injected in large skeletal muscle – deltoid, triceps, gluteus maximus, rectus femoris Muscles are very vascular & less nervous supply. Less painful but self administration is not possible Depot preparation can be injected by this route

c…Intravenous (i.v.): 

c…Intravenous ( i.v .) Injected as a bolus / slowly in the superficial vein Blood directly reaches the blood stream and effects are produced immediately Highly irritant drugs given – as intima is insensitive Thrombophlebitis, necrosis of adjoing tissue etc Only aqueous solutions (not suspensions) given Bioavailability is 100% Titration of dose with is response is possible Most risky route – vital organs are directly exposed

d…Intradermal (i.d.): 

d… Intradermal ( i.d .) Drug is injected by raising a bleb (BCG vaccine) Scarring / multiple puncture of epidermis through a drop of the drug (small pox vaccine)

Transdermal delivery : 

Transdermal delivery Drug is released from the reservoir at constant rate over many hours It Penetrates the epidermis and subepidermal ---connective tissue where it enters blood capillaries. Only a very few drugs can be applied transdermally. The feasibility of this route is determined by both the physicochemical properties of the drug and the therapeutic requirements

PowerPoint Presentation: 

The ROA is determined by the physical characteristics of the drug, the speed which the drug is absorbed and/ or released, as well as the need to bypass hepatic metabolism and achieve high conc. at particular sites Important Info

PowerPoint Presentation: 

No single method of drug administration is ideal for all drugs in all circumstances Very Important Info!

PowerPoint Presentation: 

Thank you ….