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Routes of drug administration

Compiled by Sarafadeen Adebayo, Ph.D. Routes of drug administration. To describe the various routes of drug administration Relate dosage forms and route of absorption to the potential rapidity of absorption/therapeutic activity.

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Routes of drug administration

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  1. Compiled by Sarafadeen Adebayo, Ph.D. Routes of drug administration

  2. 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 Objectives

  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.

  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.

  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.

  6. Rectal • Most commonly used for suppository or enema. • Some drugs given by this route include: • aspirin, • dipyrone, • paracetamol • theophylline • Chlorpromazine • some barbiturates

  7. Merits & Demerits of Rectal Administration?? • ………… • ………….. • ……………. • ………………

  8. Some Parenteral Routes of Administration

  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

  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.

  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.

  12. Subcutaneous • This involves administration of the drug dose just under the skin.

  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.

  14. Disadvantages: • Can be painful • Irritant drugs can cause local tissue damage • Maximum of 2 ml injection thus often small doses limit use.

  15. Intramuscular • Injection administered into the: • deltoid muscle of the buttock or • gluteal muscle of the upper arm.

  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

  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.

  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

  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.

  20. Example of Drugs administered by inhalation into the lungs

  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.

  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.

  23. ***END OF PRESENTATION*** • QUESTION/DISCUSSION SESSION

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