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Route of Drug Administration
In this topic we will study “how introduce drug to the body?” now a days there are different techniques to prepare drug Like tablet, capsules, lozenges, syrup, suspension, injection, etc. thus the type of preparation of medicine the route of administration differs. Such medicines like OINTMENT apply topically, TABLET/ CAPSULE & SYRUP take orally, and Injection takes IV & IM. The advantages for studying the topic i.e. we are able to prepare such medicament for patient compliance. Paediatric/child & elder patient not responses to solid dosage forms like tablet/capsule, hence liquid or injectable preparations are helpful. While unconscious patients the injectable route is very important.
The route of administration of drug classify in three major classes. These are…
• Enteral route
• Parenteral route
• Local application
1. Enteral route
The Enteral route of drug administration is arrived from Greek language, enteron means intestine. Hence enteral route indicate the absorption of drug take place in gastro intestinal tract (GIT). The Enteral route further classified in three classes’ i.e.
• Oral route
• Sublingual route
• Enema/rectal route
In the oral route of drug administration, where the medicine placed in mouth cavity & swallowed with drinks like water, milk, etc.
Then absorption of drug takes place in GIT. The preparations used for oral route are Tablet, capsule, syrup, suspension, etc.
• Most commonly used.
• Very economical.
• No special skill is required.
• Self medication is possible.
• No complicated process required to administer the drug.
• Not useful in clinical emergencies.
• Not useful in unconscious/coma & inco-operative/child patients.
• Not useful in some preparation/drug who not suitable for GIT or alter the absorption of drug.
• The bad taste & odour of drug avoid administration.
• The drug damaged gastric mucosa not suitable to take orally.
In the sublingual route drug placed bellow the tongue, whereas the large capillary network & thin epithelium layer improves the faster absorption of drug and produce onset of action. In clinical emergencies like in Asthma Ephedrine HCl tablet given by sublingual route. In Angina Nitroglycerine tablet given by sublingual route.
• Onset of action or very fast acting useful in emergencies like Asthma & Angina.
• Very easy to reverse the drug effect by spiting tablet.
• The drug inactivation is avoided.
• May produced direct or toxic cardiac side effects if drug reaches large concentration in heart.
In the rectal route drug placed in rectum. The rectal route use advantageously, in the patient who not response or unconscious. The capillary network is good and absorption is better through rectum. For rectal route preparations use are suppositories, enemas, etc.
Evacuant enema used to remove faecal/flatuance. The soap solution used as Evacuant enema.
Retention enema used to retain in the rectum.
2. Parenteral route
The Greek/Latin language “PAR means beyond”, “enteral means intestinal” hence parenteral route defined as the route of drug administration other than GIT (ENTERON) or the route of drug administration where the drug directly introduced to systemic circulation. The Parenteral preparation needs special skills & training for drug administration. Special technical cares have to be taken like aseptic area, sterility, etc. the Parenteral preparation administrated by the help of NEEDLE & SYRRYNGE.
• Rapid onset of action, very important in clinical emergencies.
• Useful in unconscious & unco-operative patients.
• Useful in the patients who not able to swallow.
• GIT side effects can be tolerated.
• GIT unabsorbable drug can be given through it.
• Very good accuracy for dose administration.
• Special technical skills are required.
• Self medication not possible or need supervision.
• Not convenient & economical.
• Very difficult to reverse the drug action.
• Strict aseptic/sterile conditions have maintained.
• Skilled person required for administration.
The Parenteral route of drug administration further classify in two classes. These are
Injections are given by different route of administration these are
• Intra-venous (IV): Drug directly injected in veins. Advantages: Provide rapid onset of action. The Large quantity drug can administer by this route. Useful for Irritating or hypertonic solutions. Bioavaibility is great. Disadvantages: Maximum cares have taken, if injection leaks out from veins it may harm to tissue & from abscess cause irritation. The speed of drug administration has to constant & maintained. Difficult to reverse the drug action.
• Intra-muscular (IM): Drug directly injected into muscle mass. Advantages: useful for irritant solution/suspension. Large muscle mass is available like deltoid muscle, intragluteal, etc. offers uniform & slow absorption of drug. Disadvantages: skilled person required, if carefully not injected dangerous to damages nerves & form abscess. Limitation of maximum 10ml drug administration.
• Intra-dermal injection: drug in small quantity injected between the skin. This route mainly used for detect the allergic property of Drug. Example drug like penicillin, BCG vaccine, etc.
• Subcutaneous injection: drug injected bellow the skin. Slow absorption but constant action. Only non irritant drug used. Hypodermoclysis: if the puncture of vein is not possible in certain cases apply the procedure for large quantity of drug. In which use the loose subcutaneous tissue of buttock, thighs etc. Hypospray/jet injection: is the spray that use high velocity jets equivalent to subcutaneous injection without needle. Offers no pain.
• Intra-arterial injection: drug directly injected in to ARTERY.
• Intrathecal injection (intraspinal): drug directly injected in subarachnoid space of spine. Used for anaesthesia, antibiotics, etc.
• Intraperitoneal injection: drug directly injected in to peritoneal cavity. Maximum risk of infection or damages.
• Intramedullary injection: drug directly injected in bone marrow. Rapid onset of action.
• Intraartcular injection: drug directly injected in to joints.
The inhalation route of drug administration involved absorption in respiratory tract (liquid-gas system). In the bronchial asthma adrenaline aerosol/spray use. In surgeries oxygen supply can give by this route. Advantages: rapid onset of action. Very convenient route for surgical anaesthesia. Good for volatile substance. Disadvantages: directly reaches to heart may be dangerous & toxic. Increases in mucous secretion. Special skilled person with technical instruments required, makes very costly.
3. Local application
The local application route is also known as TOPICAL route of administration is defined as the use of drug/medicine for external part of the body like skin. The preparation used powder, gels, creams, foam, sprays, some time suppositories, etc.
• Advantages: easy to administer. Get fast and systemic effect.
• Disadvantages: some limitation like ointment base, small particle size required, etc.
By Vilas K Sonagre
Note: for privet circulation only.
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