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Different kinds of drugs are given in different ways. Many drugs work the same way by altering the cell activities once in the body.


Action in the body
Many drugs that are taken in the form of inhaling, swallowing or injecting, enter the blood stream and travel throughout the body. These drugs pass from the blood into the cells mof the tissues where the drug action occurs. Eye drops, local anesthetics and nasal sprays are the other kinds of drugs that act before entering the blood stream. The amount is too small to produce additional effects on the cells when they enter the blood. The effects of drugs may be created by altering cell activities.

Pharmacologists developed the receptor theory that can tell apart the chemical reactions in every living cell controlling the cell's activities and this theory also tells how drugsn act on cells. They act on a cell by altering one or more of these chemical reactions. These chemical reactions are not only one process between the body and a drug. Drug metabolism is the changing of drugs and is one way in which the body protects itself against drugs. Many of these drug metabolisms occur in the liver. A drug can be changed into a weaker substance longer by a diseased liver. As a result, physicians reduce drug dosage for a patient with liver disease.

Drug dependence

People who always take large amounts of drugs such as amphetamines, alcohol, barbiturates, or narcotics may become dependant on the drugs. They have a very strong physical need for a drug's effect. The person who is using the drugs must take large doses to get the desired effects. The development of physical dependence is called Drug addiction. An intense withdrawal sickness occurs if a person stops taking the drug.

Elimination from the body

The body removes drugs with other waste materials. Many drugs travel from the cells through the bloodstream to the kidneys and are eliminated in the urine. The body also removes drugs in tears, sweet and solid wastes. Some of the anesthetics are eliminated when in exhaled breath.