Chapter 7 Routes and Formulations
Routes and Formulations • The way the body absorbs and distributes drugs varies with the route of administration. • Drugs are contained in formulations and the route of administration is either enteralor parenteral. • Enteral – anything involving the alimentary canal (from the mouth to the anus). Enteral routes are oral, sublingual, buccal, and rectal. • Parenteral - any route outside the alimentary canal.
Formulations • For each route of administration, there are various formulations used to deliver the drug. • Different dosage forms affect onset, duration of action, and concentration of drug in the body. • Review pages 142-143
Local or Systemic Effect • A local effect occurs when the drug activity is at the site of administration. (eyes, ears, nose, skin). • A systemic effect occurs when the drug is introduced into the circulatory system by any route and carried to the blood to the site of activity.
Oral Formulations • Oral administration is the most frequently used route because they are easy to use, carry, and administer. • The term used to specify oral administration is peroral or PO. • Certain drugs are effected by the pH of the stomach.
Oral formulations • Liquid oral formulations generally reach the circulatory system faster than solid dosage forms. • Disintegration and dissolution are not required for when dosage is in a liquid form. • Disintegration- the breaking apart of a tablet into smaller pieces. • Dissolution – when smaller pieces of disintegrated tablet dissolve in a solution.
Solid Formulations • Tablets • Capsules • Bulk powders • Modified release
Liquid Formulations • Solutions – a clear liquid dissolved in a solvent (a liquid that dissolves another substance) • Aqueous solutions are the most common type of oral solution. Water is the solvent. • Syrups – solution that is saturated with sugar. • Nonaqueous solutions – contain solvent other than water. • Elixirs – alcohol or water based, sweetened. Not as thick as a syrup
Liquid Formulations • Spirits – alcoholic or hydroalcoholic solution that are usually used for flavoring but some are medicinal. • Tinctures - alcoholic or hydroalcoholic solution. • Suspensions – solution in which the drug does not completely dissolve in the solvent. Sweetened or flavored. Settle over time. • Emulsions – oil and water based. An emulsifier is used to make the drugs mix. • Gels – gelling agents are used to increase viscosity of the drug.
Sublingual Formulations • Tablets are placed under the tongue in sublingual administration. • When the drug is released from the tablet, it is quickly absorbed into the circulatory system since the membranes in the mouth are very thin and there is a good blood supply. • Nitroglycerin is the best known. • Limitations to sublingual • Condition of the mouth • The patient • Unpleasant taste to hold in mouth
Buccal Formulations • Buccal cavity are the insides of the cheek. • Tablets and lozenges are placed in the pouch between the cheeks and the teeth to dissolve. • Rapid absorption of drugs.
Rectal Formulations • Drugs are administered via the rectum for a local effect or to avoid degradation after oral administration. • If oral administration is unavailable because the patient is vomiting, unconscious, or unable to swallow oral formulations, the rectal route is an option. • Disadvantages: • Pt’s don’t like it • Absorption is unpredictable • Most common rectal formulations are: • Suppositories – melt when inserted • Solutions – enemas or cleansing • Ointments - local effect, hemorrhoids
Parenteral Routes of Administration • Parenteral – a route of administration outside the alimentary tract. Alimentary - the organs from the mouth to the anus. The GI tract is a portion of the alimentary tract. • Parenteral routes include: Intraocular Intranasal Inhalation Injections Dermal Vaginal
Parenteral Routes • Uses: • Oral drug is poorly absorbed or degraded by stomach acid • Rapid drug response is desired • Uncooperative patient • Unconscious patient
Parenteral Routes of Administration • Disadvantages: • Cost • Requires skill to administer • Can’t take it back • Risk of administration, ie. Blood clots, infection
Parenteral Routes of Administration • Several parenteral routes require a needle and syringe. • Intravenous – injected directly into a vein • Intradermal – administered into the top layer of the skin • Intramuscular – administered into a muscle • Subcutaneous – administered into the subcutaneous tissue of the skin
Intravenous Formulations • Intravenous dosage forms are administered directly into a vein. • It takes 20 seconds for the medication to circulate throughout the body. • Solutions are the most common IV formulations and are aqueous (water).
Complications of IV therapy • Thrombus – clot formation • Phlebitis – inflammation of a vein • Air embolism – air introduced into a vein • Particulate matter – small pieces of glass from a broken vial or ampule
Intramuscular • Less hazardous than the IV route but many people experience pain at the injection site. • Risks include: hematoma, scar formation, embolism, cyst. • Injection site should be as far away from major nerves to avoid nerve injury or damage. • Only 2 – 5 mL of solution can be given, amount depended on site. Larger muscle, more medicine.
Subcutaneous • Injection or insertion of a device beneath the surface of the skin. • Insulin is given by the SQ route • Risks similar to IM • Maximum amount of fluid is 2 mL.
Intradermal • Small volumes that are injected into the top layer of skin. TB test is only 0.1 mL of solution. • Intradermal injections forms a wheal, or raised blister like area.
Ophthalmic Formulations • Used for local treatment of the eye. • Formulations are sterile and are either suspensions or solutions. Ointments and inserts are available. • Disadvantages: • Loss of dose due to spillage. • Tears wash away medication • Drug can get to systemic circulation • Can be difficult to use
Intranasal Formulations • Nasal cavity can hold about 20 mL (or 4 tsp), which is a very large surface area and has a rich blood supply. • Primarily used for decongestant activity on the nasal mucosa. • Blood concentrations are about equal to IV formulations. • Route being considered for insulin delivery. • Disadvantages • Should not be used for prolonged periods. • Drug often swallowed because often difficult to administer
Inhalation Formulations • Drugs intended to reach the pulmonary system. • Large surface area and rich blood supply, but due to inconsistencies in absorption the route is not as good as IV. • Gaseous and anesthetics are the most important drugs given this route. • Most dosage forms are aerosols.
Dermal Formulations • For local effects on or with in the skin. • Dosage formulations are lubricants, drying agents, protectants, emollients, etc. and are used for a variety of skins conditions. • Some dermal dosage formulations promote percutaneous absorption (through the skin) and used for birth control, cardiac disease, depression, smoking cessation, etc. and cause a systemic effect. • Advantages: • ease of administration • easily removed if needed. • Disadvantages: • absorbed amount is limited.
Vaginal Formulations • Used generally for localized effects. • Formulations for this route are solutions, ointments, creams, foams, suppositories, tablets, and IUD (contraceptive device). • Disadvantages: • Variable absorption • Toxic Shock Syndrome risk – TSS is a bacterial infection in the blood.