[pharma] routes of drug administration
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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
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.
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.