Routes of administration

Routes of administration

Content

General Pharmacology

•       Routes of administration

•       Advantages and disadvantages of various routes of administration

•       Differentiate between oral and parental route

Intended Learning Outcomes

At the end of this lecture, student will be able to

•       Classify various routes of administration

•       Explain the advantages and disadvantages of various routes of administration

•       Differentiate between oral and parenteral route of administration

Routes of administration

Parenteral Route

•       Advantages

–      Unconscious, unco-operative patient

–      Patients with vomitting and diarrhoea

–      Drugs irritating stomach

–      Avoid FPM, drug modification by GIT juices or liver enzymes

–      Rapid action

–      Accuracy of dose

•       Disadvantages

–      Inconvenient

–      No self-medication

–      Liable to cause infection

–      Injury to arteries/ nerves

–      Expensive

Parenteral Route – Injections 

Intradermal

•       BCG vaccine

•       Given to the layers of skin, Painful

•       Small quantity can be administered

•       Employed for testing drug sensitivity

Subcutaneous

•       Commonest – insulin

•       s.c. drug implants depot therapy - Sex hormone implants

•       Only non-irritant substances

•       Absorption slower than i.m.

•       Unreliable in shock

Intramuscular

•       Soluble substances, mild irritants, suspensions, colloids

•       Rate of absorption – Reasonably uniform, rapid onset

•       Volume should not exceed 10 ml

•       Diazepam, hydrocortisone, phenytoin, digoxin

•       May cause local pain or necrosis - Quinine, paraldehyde

•       Care to avoid nerve damage

•       Child – to the lateral thigh

Intravenous

•       Directly into the vein and rapid action

•       Desired blood conc obtained rapidly with well-defined dose

•       Precautions:

–      Needle position should be ensured

–      Irritating solutions – Piggybacking into a running i.v. drip

•       Disadvantages:

–      Local irritation can lead to phlebitis

–      No Self medication

–      Extravasation – severe irritation, sloughing

•       Drug may be injected:

–      As a bolus (Furosemide)

–      Over 5-10 min (Aminophylline in 10-20 ml of isotonic glucose/ saline

–      In an infusion 50-100 ml

–      Infusion is employed:

–      To slow the administration of drug to avoid toxicity – Morphine

–      To maintain a constant plasma level – insulin/ dopamine

–      To administer larger volume– Fluid in shock / dehydration

Intra-arterial route

–      Into artery

–      Used in diagnostic studies – Angiogram, embolization therapy

–      Antimalignancy compounds – localised malignancies

Intraperitoneal route

–      Large surface area for absorption

–      Infants – giving fluids

–      Peritoneal dialysis

Intrathecal

–      Into sub-arachnoid spaces

–      Drugs act directly on CNS

–      Strict asceptic precautions

–      Antibiotics

–      Antimalignancy compounds

Epidural/ Extradural

–      Over the dura mater

–      Lignocaine

Intraosseous

–      Into bone marrow of iliac crest or tibia

–      Rapid absorption

–      Adrenaline in severe shock with sudden cardiac arrest

Intra articular

–      Directly into a joint

–      Hydrocortisone acetate in RA

–      High local conc of drug

II. Transcutaneous

•       Iontophoresis

–      Galvanic current allows the penetration of drugs applied into the skin into the deeper tissues

–      Anode Iontophoresis: for +ve compounds

–      Catode Iontophoresis: for –ve compounds

–      Eg. salicylates

•       Inunction

–      Rubbed into the skin

–      NG ointment in Angina Pectoris

•       Jet injection

–      High velocity jet produced through a micro fine orifice

–      No needle

–      Insulin

•       Adhesive unit

–      Deliver the drug slowly

–      Scopolamine for motion sickness

III. Transmucosal

•       Sublingual

–      NG in angina pectoris

–      Buprenorphine as analgesic

•       Transnasal

–      GnRH, calcitonin

•       Transrectal

–      Indomethacin in RA

–      Diazepam in SE

•       Endotracheal

–      Adrenaline, atropine, diazepam, lignocaine

IV. Inhalation Route

•       Produce rapid effects

•       Drugs directly to the left side of the heart

•       May produce cardiac toxicity

•       By pressurised metered aerosols – Salbutamol, beclomethasone in bronchial asthma

•       Dry powders from inhalers – Salbutamol

•       Oxygen or compressed air driven nebulised solution

•       Gases-  General anaesthetics

Summary

•       Routes of administration: Oral and Parenteral

•       Parenteral includes intravenous, intramuscular, intrathecal, intradermal, subcutaneous

•       Parenteral routes are useful in unconscious, unco-operative patient, patients with vomitting and diarrhea, drugs irritating stomach

•       Inhalational routes produce rapid effects, drugs directly enter  into left side of the heart and may produce cardiac toxicity

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