- The way in which the body absorbs and distributes drugs varies with the route of administration and the dosage form used
- Enteral refers to anything involving the alimentary tract from the mouth to the rectum. There are four enteral routes: oral, sublingual, buccal, and rectal
- Parenteral refers to anything next to or beside the enteral route. Some parenteral routes use formulations that are injected. Other parenteral formulations do not require injection
- A local effect occurs when the drug activity is at the site of administration (e.g. eyes, ears, nose, skin)
- A systemic effect occurs when the drug is introduced into the circulatory system and carried to the site of activity
Enteral Routes and Formulations
- Oral administration means the dosage form is to be swallowed
- Drugs administered in liquid dosage forms generally reach the circulatory system faster thand rugs formulated in solid dosage forms
- The primary goal of modified release dosage forms is to reduce the number of doses a patient must take per day
- The mouth has two enteral routes of administration: sublingual (under the tongue) and buccal (in the cheek pouch)
- Rectal administration is used for both systemic and local effects. Suppositories, ointments, and solutions are common dosage forms
Parenteral Routes and Formulations
- Some parenteral routes requiring injection for administration are intravenous, intramuscular, intradermal, and subcutaneous. Intravenous solutions must be sterile (bacteria free) and free of particulate material
- Intramuscular injections generally result in lower but longer lasting blood concentrations than with intravenous administration
- The subcutaneous route can be used for both short term and very long term therapies. Insulin is the most important drug routinely administered by this route
- Intradermal administration is used for diagnostics, desensitization, and immunization
- Ophthalmic administration can lead to a significant loss of dose due to spillage and drainage
- Intranasal administration of some drugs produce blood concentrations similar to intravenous administration
- Inhalation dosage forms deliver drugs to the lungs. MDI aerosols, dry powder inhales, and nebulizers are common devices used to administer drugs by this route
- Dermal formulations vary from solutions and lotions to aerosols, ointments, and pastes. Transdermal patches are also common dosage forms
- Vaginal dosage forms (e.g. suppositories, tablets, solutions) are most often used for local effect. However, long term systemic effects can be achieved with IUDs
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