Routes of Administration & Dosage Forms

1. Routes of Administration & Dosage Forms BA-FP-JU-C

2. The oral route The most frequently used route for local and systemic treatments…Why? Advantages:Convenient , simple ,safe, cheap, variety of forms. Disadvantages: • Slow onset of action. • Variable gastric emptying (factors). • Possibility of irregular or poor absorption ( low bioavailability). • Drug solubility may be altered by some substances in the GIT (e.g. Ca+2). • Destruction of certain drugs in the GIT (due to enzymes or secretions). • First pass effect (i.e. presystemic metabolism). • Not suitable for unconscious or vomiting patients and for pre- or post-operative use. Examples: Tablets, suspensions, solutions, emulsions, powders, granules, capsules, gels, elixirs. BA-FP-JU-C

3. The buccal/sublingual route Two sites are used for absorption from the buccal cavity: • For sublingual absorption, the area under the tongue is used: Very fast onset of action but with short duration. 2. For buccal absorption, the buccal sulcus is used. This is the area between the upper lip and the gum: Fast onset of action and longer duration than the sublingual routes. 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. BA-FP-JU-C

4. The buccal/sublingual route Advantages: • Quick onset of action. • Rapid absorption - Because of the good blood supply to the area absorption is usually quite rapid. • Avoiding the first pass metabolism: As the liver is by-passed, there is no loss of drug leading to higher bioavailability. • Drug stability: pH in mouth relatively neutral (stomach - acidic). Thus a drug may be more stable. • Can be administered to unconscious and vomiting patients (e.g. antiemetic drugs). Disadvantages: • Holding the dose in the mouth is 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. BA-FP-JU-C

5. The parenteral route This route describes drug administration by injection such as • Intravenous route (i.v.): Very fast onset of action. • Subcutaneous route (s.c.): The easiest and least painful type of injection to administer. • Intramuscular route (i.m.): The drug can be formulated in an aqueous solution (fast onset), a suspension or in an oily vehicle (slower onset and more prolonged action). BA-FP-JU-C

6. The parenteral route Advantages: • Rapid - Total dose - Large doses can be given by extending the time of infusion. • GI stability Disadvantages: • Requires trained personnel . • Suitable vein – Safety issue. • Expensive - Sterility, pyrogen testing or preparation, transport and storage. BA-FP-JU-C

7. The rectal route • More local than systemic. • Examples: suppositories, ointment, creams, powders, enemas and tablets. Advantages: • Can be used when the oral route is unsuitable (vomiting, unconscious and uncooperative patients). Can also be used when the drug causes GIT irritation. • Only some of the drug absorbed from the rectum will be subject to the first pass effect (much less than the oral route). Disadvantages: • Erratic or irregular absorption : Absorption is often incomplete and may give rise to a variable effect. • Inconvenient. P.S. Similar properties to the vaginal route. BA-FP-JU-C

8. The topical route • Applied to the skin: • Mainly to local effect such as antifungals. • But may also be systemic ( nitroglycerine cream): Avoids first pass effect and provides close to zero-order kinetics over prolonged time intervals. • Also applied to other topical surfaces such as • Eye (ophthalmic preparations), • Ear (otic or aural preparations) • Nose (nasal dosage forms). • Examples: Ointments, creams, pastes, lotions, gels, solutions, topical aerosols. BA-FP-JU-C

9. The inhalation (respiratory) route • Drugs are administered usually by inhalation through the nose or mouth. • Mainly for local effect such as bronchodilators (treatment of asthma) • And can be used to produce a systemic effect (such as general anesthesia). • The lungs provide an excellent surface for absorption (in the alveolar region) when the drug is delivered in gaseous or aerosol. • 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. • Examples: Aerosols (solution, suspension, emulsion, powder forms), inhalations, sprays, gases. BA-FP-JU-C

10. Dosage Forms • Drug substances (i.e. active pharmaceutical ingredients) are seldom administered alone, but rather as a part of a formulation in combination with one or more non-medical agents (i.e. excipients) that serve varied and specialized pharmaceutical functions. BA-FP-JU-C

11. Pharmaceutical Ingredients can serve several functions • solubilize • suspend • thicken • dilute • flavor • color • emulsify • stabilize • preserve BA-FP-JU-C

12. Types of Dosage Forms • Solutions • Syrups • Elixirs • Suspensions • Emulsions • Creams • Ointment • Lotions • Capsules • Tablets • Suppositories • Pessaries • Powders • Granules • Parenteral • Aerosols BA-FP-JU-C

13. Why use dosage forms? • Protection of a drug substance from destructive influences of atmospheric oxygen or humidity • Protection from influence of gastric acid after oral administration • To mask taste of offensive drugs. • To provide liquid preparations of substances that are either insoluble or unstable • To provide clear liquid dosage forms BA-FP-JU-C

14. Why use dosage forms? • To provide time-controlled release of drugs • To provide optimal topical administration • To provide for the insertion of a drug into one of the body’s orifices • Provide for placement of drugs into the blood stream • Provide for lung inhalation of drugs BA-FP-JU-C

15. Key points *The route can be chosen to give local or systemic effects, fast or slow *The oral route is the most commonly used route *Gastric emptying, stability and other materials present in the GIT may limit availability of drug from the oral route *Sublingual absorption gives a short, fast-onset activity BA-FP-JU-C

16. Key points *Buccal absorption takes place between the gum and lip. This route can be used with unconscious patients and to avoid first pass metabolism *Rectal absorption partially avoids first pass metabolism. It is useful for nil-by-mouth patients and in cases of gastric irritation. *Inhalation requires a much lower dose than the oral route, with a rapid onset BA-FP-JU-C

17. Key points *Administration to the skin maybe used for both local and systemic effects *Injections can give the fastest onset of action but prolonged action is also possible using oily intramuscular injections. *A wide range of different dosage forms have been devised which have different properties and uses. *The same drug may usefully be used in different formulations to assist different types of patients. BA-FP-JU-C