1. Routes of drug administration
Compiled by
Sarafadeen Adebayo, Ph.D.
Wednesday, April 26, 2017

2. Objectives To describe the various routes of drug administration
Relate dosage forms and route of absorption to the potential rapidity of absorption/therapeutic activity.
To understand the advantages and disadvantages of the various routes of drug administration
Wednesday, April 26, 2017

3. Buccal/Sublingual
Buccal or sublingual dosage form enable drugs to be taken as smaller tablets held in the mouth or under the tongue.
Buccal tablets are often harder tablets [4 hour disintegration time], designed to dissolve slowly.
Nitroglycerin, as a softer sublingual tablet [2 min disintegration time] may be used for the rapid relief of angina.
This ROA is also used for some steroids such as testosterone and oxytocin while nicotine-containing chewing gum may be used for cigarette smoking replacement.
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4. Advantages of buccal sublingual administration:
First pass - The liver is by-passed thus there is no loss of drug by first pass effect for buccal administration. Bioavailability thus is higher.
Rapid absorption - Because of the good blood supply to the area absorption is usually quite rapid.
Drug stability - pH in mouth relatively neutral (cf. stomach - acidic). Thus a drug may be more stable.
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5. Disadvantages Holding the dose in the mouth may be inconvenient.
If any is swallowed that portion must be treated as an oral dose and subject to first pass metabolism.
Small doses only can be accommodated easily.
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6. Rectal Most commonly used for suppository or enema.
Some drugs given by this route include:
aspirin,
dipyrone,
paracetamol
theophylline
Chlorpromazine
some barbiturates
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7. Merits & Demerits of Rectal Administration??
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8. Some Parenteral Routes of Administration
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9. Intravenous
Drugs may be given into a peripheral vein over 1 to 2 minutes or longer by infusion.
Rapid injections are used to treat epileptic seizures, acute asthma, or cardiac arrhythmias
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10. Advantages of IV Rapid - A quick response is possible
Total dose - The whole dose is delivered to the blood stream. Large doses can be given by extending the time of infusion.
Veins relatively insensitive to irritation by irritant drugs.
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11. Demerits of IV Suitable vein may be difficult to locate.
May be toxic - Because of the rapid response, toxicity can be a problem with rapid drug administrations
could then be given as an infusion while monitoring for toxicity.
Requires trained personnel
Expensive - Sterility, pyrogen testing and larger volume of solvent means greater cost for preparation, transport and storage.
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12. Subcutaneous
This involves administration of the drug dose just under the skin.
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13. Advantages: Can be given by patient, e.g. in the case of insulin
Absorption slow but usually complete.
Absorption rate can be improved by massage or heat.
Vasoconstrictor may be added to reduce the absorption of a local anesthetic agent, thereby prolonging its effect at the site of interest.
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14. Disadvantages: Can be painful
Irritant drugs can cause local tissue damage
Maximum of 2 ml injection thus often small doses limit use.
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15. Injection administered into the: deltoid muscle of the buttock or
Intramuscular
Injection administered into the:
deltoid muscle of the buttock or
gluteal muscle of the upper arm.
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16. Advantages: Larger volume, than sc, can be given by IM
A depot or sustained release effect is possible with IM injections, e.g. procaine penicillin
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17. Disadvantages: Trained personnel required for injections.
The site of injection will influence the absorption, generally the deltoid muscle is the best site
Absorption is sometimes erratic, especially for poorly soluble drugs, e.g. diazepam, phenytoin.
The solvent maybe absorbed faster than the drug causing precipitation of the drug at the site of injection.
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18. Inhalation
Drugs administered as fine particles of liquids or solids or as aerosols or spray.
The drug may be required for local or systemic effects.
Local effect - bronchodilators
Systemic effect - general anesthesia
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19. Merits Rapid absorption, by-passing the liver
Absorption of gases is relatively efficient, however solids and liquids are excluded if larger than 20 micron and even then only 10 % of the dose may be absorbed.
Wednesday, April 26, 2017

20. Example of Drugs administered by inhalation into the lungs
Comments
Corticosteroids
Beclomethasone dipropionate, betamethasone valerate & triamcinolone acetonide used for relief of brochial asthma
Ergotamine tartrate
Available as a pressurized aerosol preparation & provides relief from migraine much faster than from oral preparations
Sympathomimetics
Fenoterol, rimiterol, salbutamol, salmeterol, & terbutaline are well absorbed from the lungs giving early relief from asthmatic attack.
Sodium cromoglycate
Well absorbed from the lungs when administered as a fine powder or spray but poorly absorbed from the gastro-intestinal tract. Inhalation of the powder may cause bronchospasm; isoprenaline may be administered concurrently to minimize this effect.
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21. Topical
Local effect - eye drops, antiseptic, sunscreen, callous removal, etc.
Systemic effect - e.g., nitroglycerin ointment.
Absorption through the skin, especially via cuts and abrasions but also intact skin, can be quite marked.
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22. Other Routes of Administration
Intra-nasal - some systemic absorption has been demonstrated for propranolol and some low dose hormones
Intra-arterial for cancer chemotherapy to maximize drug concentrations at the tumor site
Intrathecal directly into the cerebrospinal fluid.
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23. ***END OF PRESENTATION***
QUESTION/DISCUSSION SESSION
Wednesday, April 26, 2017