Route of drug administration
Route of drug administration means way of getting a drug into the body. It's classified into two categories mainly:
1) Enteral:
Refers the routes from the mouth to the rectum where the drug is passed through
the GIT. There are 4 enteral routes of administration: Oral, Sublingual, buccal
& rectal.
2) Parenteral:
Routes through which the drug directly reaches the body fluids. Here, injection
or infusion is induced by means of a needle or catheter inserted into body.
Oral route
Oral route is the most common & convenient systemic route. Here the medication is applied topically to the mouth & the drug is absorbed from the stomach & small intestine.▪ Advantages :
1) Safest
& convenient route
2) Painless
method
3) Cost
effective
4) No
maximal/strict sterilization is required
5) No extra
skill required, self-medication is possible.
▪ Disadvantages
:
1) Slow
absorption of drug, hence slow action.
2)
Unpalatable & bitter drugs may be unpleasant in taste
3) Not useful
for unconscious & vomiting patients.
4) Effect is
too slow in case of emergency
5) Drugs may
undergo 1st pass effect in the liver
6) Some drugs
get destroyed by gastric secretion
Sublingual/Buccal Route:
Here the drugs are taken as smaller tablets, which are held in the mouth(buccal) or beneath the tongue(sublingual). The route has special importance for certain drugs.e.g. Motrogly is effective when given in S/l route but ineffective when given orally.
▪ Advantages :
1) Painless
method
2) Cost
effective
3) No
maximal/strict sterilization is required
4) No extra
skill required, self medication is possible.
5) Drug
absorption is quick by S/l mucosa
6) Rapid
onset of action.
7) 1st pass
effect avoided.
▪ Disadvantages :
1) Irritation
of oral mucosa may occur
2)
Unpalatable & bitter drugs may be
unpleasant in taste
3) Not useful
for unconscious & vomiting patients.
4) Large
quantities of drugs can't be given
Inhalational
It provides rapid delivery of drugs across the large surface area of respiratory tract. In this way drug can pass directly to the lungs. Drugs used involve volatile drugs & gases.▪ Advantages :
1) Rapid onset of action.
2) Rapid
absorption of drugs.
3) 1st pass metabolism effect avoided.
4) Self
medication is possible.
▪ Disadvantages :
1) Special
apparatus is required.
2) Fewer dose
can be given at a time
3) Irritation
of respiratory tract may take place
4)
difficulties in regulating the exact amount of dose.
Intravenous route
Most common Parenteral route for the drugs that aren't absorbed orally. The drug is injected or infused directly into the blood stream via veins.▪ Advantages :
1)
Bioavailability is 100%
2) Rapid
onset of action.
3) 1st pass metabolism avoided.
4) Suitable
for irritant & unpalatable drugs.
5)
Suitable for vomiting & unconscious
patients.
6) No
food-drug interaction occur.
7) Mild
irritants can be given.
▪ Disadvantages:
1) Irritation
of vein can cause thrombophlebitis.
2) Local
abscess & pain.
3) Chance of
infection.
4) Relatively
expensive than enteral drugs.
5) Technical
assistance is required.
6) Cannot be
recalled by strategies such as emesis or by binding to activated charcoal.
Intramuscular route
Drug injected into the skeletal muscle like deltoid, gluteus, rectus femoris.▪ Advantages :
1) High
Bioavailability (75% to <100%)
2) Rapid
onset of action.
3) 1st pass metabolism avoided.
4) Suitable
for irritant & unpalatable drugs.
5)
Suitable for vomiting & unconscious
patients.
6) No
food-drug interaction occur.
7) Mild
irritants can be given.
▪ Disadvantages :
1) Only upto
10 ml of drug can be given.
2) Local
abscess & pain
3) Chance of
infection with necrosis.
4) Relatively
expensive than enteral drugs.
5) Technical
assistance is required.
6) Cannot be
recalled by strategies such as emesis or by binding to activated charcoal.
Subcutaneous route
The drug is injected under the skin. Drug is absorbed in the Sub-cutaneous tissues.▪ Advantages :
1) High
Bioavailability (75% to <100%)
3) 1st pass metabolism avoided.
4) Suitable
for bitter & unpalatable drugs.
5)
Suitable for vomiting & unconscious
patients.
6) No
food-drug interaction occur.
7) Minimized the risks associated with IV inj.
▪ Disadvantages :
1) Absorption
is slow due to less vascular tissues.
2) Irritants
can't be given.
3) Only small
volume (upto 2ml) can be injected.
4) Local
abscess & pain
5) Chance of
infection with necrosis.
6) Cannot be
recalled by strategies such as emesis or by binding to activated charcoal.
Intradermal route
The drug is injected into the skin layer(dermis). The drug is slowly absorbed. Only small amounts of drug can be given.Transdermal route :
This route
of administration achieves systemic effects by application of drugs to the
skin, usually by transdermal patch. The rate of absorption depends upon the
physical characteristics of skin at the site of application.
This route
is most often used for the sustained delivery of drugs, such as the antianginal
drug nitroglycerin, the antiemetic scopolamine.
[Note : According to applied sites of drugs Routes of drug administration can be divided into 2 forms. These are :
- Systemic routes. (All of the routes described above are systemic routes)
- Non-systemic/Local routes]
Topical routes
Topical route is non-systemic route. Topical route is used when a local effect of the drug is required. The drug is applied to the skin surface or mucus membrane in the form of Ointments, creams, lotions and powders .▪
Advantages :
1) Local
therapeutic effects.
2) Lower risk
of side effects.
3) Relatively
Cheaper than parenteral products.
4) No 1st Pass metabolism takes place.
5) The drug can be self administered.
▪ Disadvantages :
1) Absorption
is slow.
2) Effect is
slow.
3) Skin
irritation or necrosis may occur.
4) Irritants
can't be given.
5) The
dosage is difficult to control.
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