DRUG TOXICITY

Drug toxicity refers to the poisonous and potentially dangerous effects of some drugs. Idiosyncrasy is an example of an unpredictable type of drug toxicity.

Other types of drug toxicity are more predictable and based on the dosage of the drug given. If the dosage of certain drugs is increased, unfavorable effects may be produced. Physicians are trained to be aware of the potential toxic effects of all drugs they prescribe and must be cautious with their use. Disorders directly resulting from diagnostic or therapeutic efforts of a physician are known as iatrogenic, and are usually related to drug toxicity.

Side effects are toxic effects which routinely result from the use of a drug. They often occur with the usual therapeutic dosage of a drug and are usually tolerable. Doctors can anticipate these reactions and tell a patient what to expect. For example, many of morphine`s harmful effects are side reactions and should therefore be expected. Nausea, vomiting, and alopecia are common side effects of the chemotherapeutic drugs used to treat cancer. Most drugs cause weak side reactions that do not prevent use of the drug.

Hypersensitivity reactions, also called allergic reactions, occur only in people allergic to a particular drug. Some of these reactions are minor but others are severe. Any drug may cause an allergic reaction in people highly sensitive to that drug. Some people cannot take such common drugs as aspirin or penicillin because they are allergic to them.

Toxic reactions result from drug poisoning. Such reactions damage cells and may kill a person. All drugs can have a mild toxic effect, and a large enough overdose of any drug will produce a severe toxic reaction.

Adverse reactions: adverse events reported in U. S.- controlled studies include bradycardia, edema, headache, dizziness, fatigue, lethargy, insomnia, nervousness, bizarre dreams, depression, impotence, dyspnea, pharyngitis, rhinitis, upper respiratory infection, dyspepsia, nausea, diarrhea, chest pain, arthralgia, and rash.

In European-controlled clinical trials the following adverse reactions were noted: bradycardia, palpitation, edema, cold extremities, headache, dizziness, fatigue, asthenia, insomnia, paresthesia, nausea, dyspepsia, diarrhea, chest pain, joint pain, and myalgia.

Contraindications are factors in a patient’s condition which make the use of a drug dangerous and ill-advised. For example, in the presence of renal failure, it is unwise to administer a drug which is normally eliminated by the kidneys.

Among the most dangerous toxic complications of drug usage are blood dyscrasias (blood diseases) such as aplastic anemia and leucopenia, cataract formation (eye disorder), cholestatic jaundice (biliary obstruction leading to yellow discoloration of skin), neuropathy, collagen disorders (connective tissue damage such as arthritis), and photosensitivity (abnornmal sensitivity to light , sinus bradycardia, heart block, cardiogenic shock, and overt cardiac failure.

Task I. Give the meaning of the following terms:

1. drug toxicity; 2. iatrogenic disorders; 3. adverse reaction; 4. indications; 5.contraindications; 6. hypersensitivity reactions; 7. drug dependence.

Task II. Match the names of adverse reactions and their explanations.

Text 4.

Date: 2015-01-02; view: 2415