[Pharma] routes of drug administration

ROUTES OF DRUG ROUTES OF DRUG ADMINISTRATIOADMINISTRATIO

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Formal Definition of Formal Definition of DrugDrug

“A drug is a chemical which is used for diagnosis, prevention and cure of a disease”

Routes of Administration of Drugs

Dugs can be given by various routes. The goal is to deliver the drug to target organ or tissue, so that it can exert its maximum effect

Major Routes

EnteralOral

SublingualRectal

ParenteralIVIM

SubcutaneousInhalationIntranasalIntrathecal

TopicalTransdermal

ENTERAL ROUTE ENTERAL ROUTE OF OF

ADMINISTRATIOADMINISTRATIONNOral

Sublingual Rectal

ORAL ROUTE OF ORAL ROUTE OF ADMINISTRATIONADMINISTRATION

By Mouth FOR SYSTEMIC EFFECT:Advantage:Convenient MethodDisadvantages: Absorption may be delayed or enhanced

after food intake. Presence of food in stomach delays gastric

emptying. So drugs like penicillin, insulin and oxytocin are destroyed in stomach by acids

FOR EFFECT IN THE GUT:

Advantage:Drug is placed at the site of action and local concentration can be higher than would be safe in blood, e.g., Neomycin, Anthelminthics.

Disadvantages: Drug distribution may be uneven and in

some diseases the whole thickness of gut wall is affected, e.g., in severe bacillary dysentery, typhoid.

Drug passes through stomach, intestinal wall and then through liver before it is transported via blood stream to target organ. The intestinal wall and liver metabolizes drug thus decreasing amount of drug reaching the blood stream.

EXAMPLES: Anthelminthics, Neomycin,Metronidazole, Omeprazole

SUBLINGUAL ROUTESUBLINGUAL ROUTEDrug is placed below the tongue. It is usually employed for rapid absorption of drug in cases of emergency. Advantages:

Quick effect is obtained as the drug bypasses liver and intestine and diffuses directly into capillary network.

Effect can be terminated by spitting out the tablet.

Prevents the destruction of drug by low pH and enzymes in stomach.

Disadvantage:Irritation of mucous membrane can occur.

EXAMPLES : Nitroglycerine, Isosorbide(angesid), Nifidepine(antihypertensive)

RECTAL ROUTE

Drug is administered through anal canal. e.g., suppositories are inserted into rectum, enema.

Advantages: Rectal mucosa has a rich blood supply so

the drug is readily absorbed. Drugs irritant to stomach can be given by

suppository, e.g. aminophylline, indomethacin

It is used in vomiting, motion sickness, in children, comatose patients and post operative patients.

Disadvantages:Disadvantages: PsychologicalPsychological Rectal inflammation may occur.Rectal inflammation may occur. Absorption may be unreliable if Absorption may be unreliable if

rectum is full of fecal materialrectum is full of fecal material.. Examples: Aminophylline, Examples: Aminophylline,

Indomethacin, Glycerin Indomethacin, Glycerin suppositories,Prostaglandinssuppositories,Prostaglandins

PARENTERAL ROUTE PARENTERAL ROUTE OF ADMINISTRATIONOF ADMINISTRATION

((It involves drug administration It involves drug administration via injection into a blood vessel, via injection into a blood vessel,

soft tissue or body cavitysoft tissue or body cavity))

ADVANTAGES

Used for drugs that are unstable in GIT.

Under conditions which require a rapid onset of action.

In treatment of unconscious patients. Used for drugs that are poorly

absorbed from GIT. Provides maximum control over actual

drug delivered to body.

DISADVANTAGES

Need of a technical staff Care of sepsis. Pain at the site of injection. Fear of needle. No retreat once the drug is injected.

INTRAVASCULAR ROUTE

Intravenous – more common

Intra-arterial - less common. It is dangerous

and has specific indications for diagnosis and

treatment, e.g. coronary angiography and

anticancer drugs

AdvantagesAdvantages

Bypasses GIT and First pass metabolism Bypasses GIT and First pass metabolism

Gives swift, effective and highly Gives swift, effective and highly predictable blood concentration of drug.predictable blood concentration of drug.

Suitable for administration of drugs that Suitable for administration of drugs that are not absorbed from gut or are irritant are not absorbed from gut or are irritant to GITto GIT

Disadvantages

Unlike drugs in GIT, those that are injected cannot be recalled by strategies such as emesis or binding with charcoal.

May introduce bacteria through contamination at the site of injection.

May induce hemolysis or other adverse reactions by two rapid delivery of high concentration of drug to plasma and tissues.

INTRAMUSCULAR ROUTE

Drugs administered IM can be aqueous solutions or specialized depot preparations

This route is suitable for moderate volume drugs, oily vehicles and less irritating substances

Injections are given deep into skeletal muscles. Most common sites are deltoid and gluteus muscles.

Example : Antibiotics and Analgesics

Advantage

Reliable and suitable for irritant drugs and depot preparations e.g. penicillin, neurolepticis and medroxyprogesterone.

Disadvantages

Not acceptable for self administration

May be painful

SUBCUTANEOUS ROUTE

In it needle is inserted deep into the fatty tissue just beneath the skin to produce slow and even absorption of drug for sustained effect.

Example: Insulin and Heparin.

Advantages:

Minimizes the risk associated with IV injection

Reliable and acceptable for self administration

Disadvantages:

Repeated injections at one site can cause lipoatrophy.

Poor absorption in peripheral circulatory failure.