Various routes for administration of drug into the human body

1. ROUTES OF DRUG
ADMINISTRATION
Mr. Jaineel Dharod (JD)
Dept. of Pharmacology, PharmD

2. Routes of Drug Administration
Routes of drug administration refer to the right
path or the required route through which a drug
has to be administered into the body to obtain
maximum benefit.

3. ◦ A drug administered into the body undergoes several chemical and metabolic
changes. These changes reduce the availability of the drug at its final site of
action in the body. For example, some drugs may not be effective when
administered orally, but may be effective when administered through injection.
◦ Choosing the correct route of drug administration reduces or bypasses these
changes, thereby helping to obtain the drug’s maximum therapeutic effect. In
addition, some drugs are maximally absorbed when they are administered
through a particular route as compared to another route. An intravenous route
of administration of the drug results in 100% bioavailability.
◦ According to the Oxford Concise Medical Dictionary, bioavailability is “the
proportion of a drug that is delivered to its site of action in the body. This is
usually the amount entering the circulation and may be low when the drugs
are given by mouth”.

4. Why select different routes?
There are several reasons which determine the preferred route of administration of a
particular drug. These include:
1. Drug properties:
A) Physical - solid, liquid, and gas. For example, drugs in gas form are given by
inhalation.
B) Chemical - solubility, pH, and irritant properties.
2. Site of desired action
A) Localized and approachable: For example, a skin lesion can be treated with
local creams so that maximal effect can be obtained and side effects on the other
parts of the body can be avoided.
B) Generalized and non-approachable: For example, oral or injection antibiotics will
be required for infections affecting the internal organs of the body.
3. Rate and extent of absorption from the drug administration site: Drugs used in
emergencies are usually given intravenously for quick effect.

5. 4. Effect of digestive juices and first pass metabolism: For
example, since nitroglycerine is digested to a large extent when
taken orally, it is given by alternate routes.
5. Requirement of accurate dose (of the dose in case of
intravenous or inhalational routes can be adjusted accurately
during the treatment depending on the patient’s response).
6. Patient condition and compliance (pediatric or geriatric
patients, or unconscious patients, or any disease conditions). For
example, unconscious patients cannot take drugs orally.
Compliance refers to whether the patient follows medical advice
correctly or not.

6. Classification of Various Routes
Systemic Local
Enteral (GIT) Parenteral
• Oral
• Sublingual
• Buccal
• Rectal
• Inhalational
• Transdermal
• Injection
Intravenous
Intramuscular
Intradermal
Subcutaneous
Intrathecous
Intraatrial
Intraarticular
Intrabiliary
Intracardiac
Intracerebral
Intraperitoneal
Epidural
Topical
Intranasal
Ocular
Mucosal
Vaginal
Transdermal
Instillations
Irrigation

7. ENTERAL ROUTE
Gastro-Intestinal Tract Route

8. 1. Oral Route
◦ This is the most common and easiest route of administration where drugs are
given by mouth. Dosage forms administered orally include tablets, capsules,
syrups, effervescent powders, elixirs, and emulsions.
◦ The oral route is considered as the first choice of route of drug administration
as it is most convenient, cheap and usually a safe method of drug
administration.
◦ The orally administered medicines are mostly absorbed in the small intestine,
and to some extent in the stomach. Some orally administered drugs are
specially designed with an enteric coating to withstand the stomach’s
digestive juices and to disintegrate in the small intestine.

9. 1. Oral Route
◦ First pass metabolism is a major problem that is encountered with orally
administered drugs. The drugs absorbed from the small intestine first reach the liver
through the portal circulation. The drug concentration is reduced to some extent
by the liver before it enters the bloodstream.
◦ Hence, the oral dose is usually higher when compared with the dose administered
through other routes. The bioavailability of the orally administered drug may
increase when the liver suffers from a disease such as cirrhosis. Two or more drugs
taken together can also alter a drug’s bioavailability, and therefore dosage
adjustment may be needed.
◦ Drugs undergo first pass metabolism to a variable extent. Commonly used drugs
that undergo extensive first pass metabolism are cimetidine, lidocaine,
propranolol, nitroglycerin, diazepam, midazolam, morphine, pethidine,
imipramine, and buprenorphine. Some drugs like insulin are destroyed by the
gastric secretions and therefore cannot be given orally.

10. 1. Oral Route - Disadvantages
◦ Drugs such as aspirin or ibuprofen (NSAIDs) may irritate the gastrointestinal
tract by harming the gastric lining and aggravate existing stomach ulcers.
◦ Some drugs are poorly absorbed orally or undergo extensive first pass
metabolism, which may reduce the effectiveness of the drug.
◦ The oral route of drug administration is not preferred in:
x Unconscious patients
x Patients with restrictions to oral intake
x Patients who are vomiting
x Emergency situations where a rapid response is necessary

11. 2. Sublingual Route
◦ ‘Sublingual’ in Latin term means ‘under the tongue’. Drugs administered
through this route diffuse into the bloodstream through the tissues under the
tongue. The mucous membrane under the tongue is supplied with a bed of
rich capillaries. Therefore, the sublingual route has a faster absorption rate
when compared with the oral route.
◦ The sublingual route of drug administration has an advantage of bypassing the
liver first pass effect. As a result, a lower dose of the drug is required when
compared with the oral route. Excess drug can be spat out. The dosage forms
used sublingually include the sublingual tablets, strips, drops, and sprays.
◦ Drugs used sublingually include nitroglycerine and buprenorphine.

12. 3. Buccal Route
◦ The buccal route is the route of administration where the medicine is placed
between the gums and the inner lining of the cheek. This route of
administration has the same advantages as of sublingual route but the
difference is the site of application.
◦ Drugs used by this route include fentanyl buccal patches, nicotine tablets as
smoking cessation aid and prochlorperazine in treating nausea and vomiting.

13. 3. Buccal Route - Disadvantages
◦ May irritate the already existing open sores in the mouth.
◦ Extended-release formulations and large doses cannot be used.
◦ Inconvenience in placing on the exact site.
◦ The medicine effect will be reduced if accidentally swallowed.
◦ Nausea and vomiting may occur if the medicine is associated with unpleasant
taste.

14. 4. Rectal Route
◦ The rectal route offers a faster, safer, and low cost route of administration
when compared to several other alternative routes. The dosage forms of the
rectal route of administration include suppositories and enemas.
◦ The medicines given by rectal route are absorbed by the rectum’s blood
vessels and enter the bloodstream. A drug administered rectally has a faster
onset of action, high bioavailability, and produces less nausea when
compared with the oral route.
◦ The rectal route of administration undergoes less first pass effect and the drug
concentration is also reduced only to a slighter extent from actual drug
concentration.

15. 4. Rectal Route
◦ The disadvantage of a rectal route is an erratic or irregular absorption, and the
unacceptability of the route by some patients.
Advantages of rectal route:
◦ Best route of administration for children and elderly patients.
◦ Does not require hospital care setting and special sterile precautions.
◦ Useful for patients suffering from swallowing difficulties, bowel obstruction, and
decreased propulsive movements in the gastrointestinal tract.
◦ Helps patients with terminal stage of illness. It can be administered to
unconscious patients.
◦ Larger quantities of drugs can be used.

16. PARENTERAL ROUTE
Except Gastro-Intestinal Tract Route

17. ◦ Parenteral route of drug administration means administering the drug through
routes that bypass the digestive tract, through injections. The administration
requires skilled medical personnel who administer the medication with the help
of a syringe and needle or a catheter using aseptic precautions. The cost is
higher than that of oral dosage forms and involves the pain of the prick of the
needle, which may be scary for some.
◦ The most commonly used parenteral routes of administration are
subcutaneous, intravenous, intramuscular, and intradermal injections.

18. ◦ Rapid absorption and faster onset of action of the drug
◦ The medication bypasses the liver first pass effect
◦ No risk of degradation of the drug by digestive juices
◦ Suitable for unconscious patients
◦ Low concentration of drug required
Advantages of Parenteral Route of Administration:

19. 1. Intravenous
◦ The route by which the medicines are directly introduced into the bloodstream
through a vein is known as intravenous route of administration. The intravenous
route is considered to be the fastest route of drug administration. The injections
and the infusions are administered by this route have 100% bioavailability.
◦ Drugs used: Electrolyte fluids, buffer solutions such as lactated Ringer’s
solutions, parenteral nutrition medicines such as amino acids and vitamins,
blood and blood-related infusions.
◦ Injection sites: Peripheral lines, central lines, peripherally inserted central
catheter, midline catheter, tunneled lines and implantable ports.

20. 1. Intravenous - Disadvantages
◦ Inflammation of blood vessels could occur
◦ Not suitable for oily and insoluble preparations
◦ Permeation of fluid may occur to the surrounding tissues
◦ Special apparatus such as infusion pumps, drip chamber, peripheral cannula
and pressure bags are required

21. 2. Intramuscular
◦ The intramuscular route of drug administration involves injecting the medicine
directly into the muscle. As muscles are rich in large blood vessels, the
absorption rate is faster than subcutaneous and intradermal routes.
◦ Oily, irritant and slow-releasing preparations can be given by intramuscular
route. The disadvantage of this route is it may lead to nerve or vein damage.
◦ Drugs used: Penicillin, haloperidol, diazepam, vitamin B12, methotrexate,
platelet-rich plasma injections, vaccines such as hepatitis A, tetanus and
hepatitis B vaccine.
◦ Injection sites: Muscle area of the upper arm, buttocks or thigh.

22. 3. Sub-cutaneous
◦ A subcutaneous injection is administered under the skin into the fat layer just
below the dermis of the skin. The absorption from the subcutaneous route is
slow and sustained action as the tissue sites have fewer blood vessels. It has a
slower action compared to intravenous but faster than an intradermal route.
◦ Drugs used: Measles vaccine, insulin, morphine, etc.
◦ Injection sites: Outer area of the upper arm, abdomen, upper thigh, upper
back, and upper area of the buttock.

23. 4. Intradermal
◦ Intradermal route of drug administration involves injecting the medication into
the dermis, a layer just below the epidermis of the skin. The amount of drug
administered through this route is usually less than 0.5ml. This route has the
longest absorption time among parenteral medications and is often used for
diagnostic purposes for tests such as penicillin sensitivity, diphtheria test and
Dick test for scarlet fever. The BCG vaccine for tuberculosis is also administered
intradermally.
◦ The body’s reaction to intradermal medicines is more easily visible as the site of
administration is closer to the surface.
◦ Injection sites: Inner surface of the forearm, upper back under the scapula /
shoulder blade.

25. TOPICAL ROUTE
Locally acting

26. ◦ The word ‘topical’ in Greek means ‘of a place’.
◦ The topical route of administration refers to the application of the medicines to
body surfaces such as skin and mucous membranes and includes transdermal
patches, instillation applied to the eye, drops placed into the ear or
medications applied to the surface of the tooth.
◦ These are painless in contrast to the parenteral route.
◦ A few drugs like desmopressin are administered nasally.

27. 1. Transdermal patches
◦ A transdermal patch is a medicated adhesive patch which is placed over the
skin to deliver specific or controlled dose into the bloodstream for a period of
time. The drug enters the blood stream by a process of diffusion at a controlled
rate. It is convenient to use. The disadvantages of this route are that it can be
used only for the drugs with small molecules which can penetrate the skin.
◦ Drug patches used: Nicotine patches, contraceptive patches, opioid patches,
nitroglycerin patches, clonidine patches and estrogen patches.
◦ Application sites: Upper chest, upper outer arm, hip, lower abdomen

28. 1. Transdermal patches - Precautions
◦ Apply to the clean, dry, or unbroken skin
◦ Make sure the adhesive patch sticks firmly
◦ Wash your hands after applying a patch
◦ Use only one patch at a time
◦ Patches are to be removed while undergoing x-ray or MRI scan
◦ If any skin irritation develops, the application site should be changed. Rotation
of application sites is encouraged
◦ The removed patches should be disposed of safely by folding the sticky sides
together to avoid contact with children
◦ If the patch falls off completely do not reapply but use the fresh one as per the
dosing schedule

29. 2. Instillations
Instillations include liquids or semisolid preparations introduced into the
conjunctival sac (eye), ear, nose and open wounds.

30. 3. Irrigation or Douching
This is used for washing the urinary bladder, vagina, uterus, and urethra; it is
mainly used for antiseptic purposes.

31. 4. Epidermic and enepidermic routes
◦ The enepidermic routes involve the application of creams, ointments, lotions,
and poultices that are applied to the surface of the skin.
◦ The Epidermic routes include the oily preparations that are rubbed onto the
skin such as rubefacients to provide counter irritation.
◦ The rubefacient dilates the capillaries under the skin and increases the blood
circulation used in treating the pain in various musculoskeletal disorders.

32. 5. Throat paints
◦ The medicines are applied to the throat to treat the
throat infections with the help of a thin brush. Glycerin is
the commonly used base to stick to the mucous
membrane for a long period of time.
◦ Examples are Iodine throat paints, Tannic acid throat
paints

33. 6. Inhalation route
◦ The inhalational route of administration is an easy method of administration where
the medicines directly pass into lungs. This route has quick action with minimal side
effects and requires a lesser dose.
◦ Drugs used: Volatile drugs and gases such as salbutamol aerosols and nebulization
or steam inhalations of tincture benzoin.
Disadvantages of Inhalation route:
◦ The airway must be accessible
◦ Special apparatus and supervision or assistance is required
◦ Irritation of the airways may occur

34. NOVEL DELIVERY
Other rarely used routes for drug delivery

35. Epidural
Administration between the dura
mater (outer membrane of the
brain) and the skull
Extra-amniotic
Administration into the space
between the fetal membranes and
endometrium inside the uterus
Intra-Arterial Administration into the arteries
Intra-Articular Administration into a joint
Intrabiliary
Administration into the gallbladder,
bile ducts or bile
Intrabursal
Administration into a bursa (fluid
filled sac which provides cushion
between the bones and tendons
Intracardiac Administration into the heart
Intracerebral Administration into the brain

36. Intracoronary
Administration into the coronary
arteries
Intracorpus cavernosum
Administration into the spaces of
corpus cavernosum of the penis in
males
Intradiscal
Administration into a disc in the spinal
cord
Intraductal Administration into the duct of a gland
Intraperitoneal
Administration into the peritoneal
cavity
Intraprostatic Administration into the prostate gland
Intrapulmonary
Administration within the lungs or the
pulmonary bronchi
Intrasinal
Administration into the periorbital or the
nasal sinuses
Intraspinal
Administration into the vertebral
column

37. Perineural
Administration surrounding a nerve
or a bunch of nerves
Retrobulbar Administration behind the eyeball
Transplacental
Administration either through or
across the placenta
Transtracheal
Administration done through the
tracheal wall
Transtympanic Administration into the middle ear
Intraovarian
Administration into the ovary in
females
Intrapericardial
Administration into the pericardium
(a sac covering the heart)
Intraosseous Administration into the bone

38. Intrasynovial
Administration into the synovial cavity of the
joint
Intratendinous Administration into a tendon
Intratesticular Administration into the testicles
Intrathecal Administration into cerebrospinal fluid (CSF)
Intratubular Administration within the organ tubules
Intratumor Administration into a tumor
Intravascular Administration within the blood vessels
Intraventricular Administration into the ventricle of the brain
Intravesical Administration within the bladder
Intravitreal
Administration into the vitreous humor of the
eye
Iontophoresis
Administration with the help of electric current
where the ions of the soluble salts migrate into
the tissues
Laryngeal Administration directly on the larynx

39. THANK YOU