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General Principles of Pharmacology |   |
| Pharmacology involves the study of drugs, and drugs are defined as chemical substances that exert a biologic effect on the recipient. Medical drugs are used for the treatment or prevention of disease, and drugs are considered useful when they can maintain, enhance or alter bodily function when a patient is cannot cope with a particular disease. |  |
Pharmacology is concerned with the following:
- the chemical and physical properties of drugs
- the physiologic effects and site of action of drugs
- how drugs exert their effects
- how the body absorbs, distributes, metabolizes, and excretes the drugs
- dosages and routes of administration of drugs
- side effects, toxicity, and contraindications
The safe administration of drugs requires awareness of the following factors:
- mode of action
- side effects
- toxicity
- range of common dosages
- rate and route of excretion
- individual differences in responses
- interaction with other drugs or food
- contraindications
For drugs to exert their expected therapeutic benefits, they need to be made available for absorption in the body's systems. Availability depends to a large extent on the route of administration of the drug. Drugs can be administered gastrointestinally, parenterally, or topically. Topical administration includes application to the skin and directly to the lungs by inhalation.
In order for a drug to be administered via inhalation, it must first either be vaporized or placed in an aerosol suspension. This generally requires the use of special equipment. The following discussion reviews the types of equipment available for administering drugs via inhalation.