Sources of drug preparations There are five main sources from which drugs are obtained: 1. Mineral : Many mineral substances found in nature are used in drugs. Examples : Iodine; zinc oxide; and magnesium sulfate (Epsom salt). 2. Plant : Certain drugs are derived from vegetables and plants. Examples : Digitalis; morphine; and senna pod extract. 3. Animal : The organs, tissues and body fluids of animals (including man) are the source of some drugs. Examples : Hormones; antitoxic serums; and gamma globulin from human blood. Types of drug preparations Drugs are compounded into various types of preparations, depending upon each drug’s physical characteristics, its intended purpose, and the method of administration. Some drugs are prepared in more than one form so they may be administered several ways. To give them bulk or form, drugs may be mixed with other substances that have no action or medicinal value. These substances are called vehicles . For a drug in aqueous solution, water is the vehicle; for a drug in an ointment, fatty substances, such as petrolatum or lanolin, are used as the vehicle. Drugs or drug mixtures that are divided into definite doses are dosage forms. Examples of dosage forms are capsules, tablets, ampules and cartridge units. Some dosage forms prepared for oral administration are enteric coated with a special coating that resists the action of the stomach juices but dissolves in the intestine. This helps prevent nausea, irritation of the stomach lining or destruction of the drug. Scored tablets are marked with an indented line across the surface so that they can be broken in half when half a tablet is the dose required. Drugs prepared with flavored coatings or in flavored vehicles are exceptionally hazardous to children if left where they have access to them. Solid preparations: ● Capsule : A drug placed in a gelatin container. Classification by therapeutic action In this major classification, drugs are grouped according to the effect they produce on the body to bring about a desired therapeutic result (as in the case of vasoconstrictors and diuretics), or according to the effect they produce on the pathogenic organism or the signs and symptoms of the disease (as in the case of fungicides, analgesics and antipyretics). A. Analgesics : These drugs are used to relieve pain without loss of consciousness. Aspirin is a mild analgesic. For relief of severe pain, morphine and opium derivative is the most valuable analgesic. B. Anesthetics : These drugs are used to produce either a general or a local loss of sensation. An example of a general anesthetic is ether, which on inhalation produces a loss of consciousness. An example of a local anesthetic is procaine hydrochloride, which, on injection by special technique, produces local analgesia. C. Antacids : Antacids are given to neutralize excess acid in the stomach. An example of an antacid is aluminum hydroxide. D. Anthelmintics : These are drugs used to rid the body of worms (helminths). An example is piperazine citrate syrup. E. Antiemetics : These are drugs used to relieve nausea and vomiting. An example is promazine hydrochloride.
4. Synthesis : Synthesis is the artificial building up of a chemical compound by the union of its elements. Drugs such as epinephrine that were once available only from natural sources can now be artificially reproduced through synthesis. Other drugs such as the sulfonamides were originally created through synthesis. 5. Microorganisms : Chemical substances produced by microorganisms such as fungi and bacteria are also sources of drugs. Examples : Penicillin; tetracycline; and vaccines. ● Tablet : A drug compressed or molded into a flat disk or other shape. ● Pill : A powdered drug molded into a sphere. The word “pill” is often misused as a general term for tablets. ● Troche : A drug preparation in a flat disk that is held in the mouth until dissolved. ● Suppository : A drug that is molded into shape for insertion into a body opening other than the mouth. Its vehicle, such as cocoa butter, melts at body temperature and the drug is released. ● Ointment : A drug suspended in a semi-solid base such as petrolatum. ● Powder : A drug that is ground up and used in powder form. Fluid preparations: ● Fluid extract : A concentrated fluid preparation. Fluid extracts are 100 percent-strength (1 ml. of the preparation contains 1 gram of the crude drug). ● Tincture : An alcoholic solution of a drug. Tinctures of potent vegetable drugs are 10 percent in strength; of less potent drugs, 20 percent in strength. ● Elixir : A solution containing water, alcohol, sugar and flavoring substances, in which one or more drugs may be dissolved. ● Spirit : An alcoholic or hydro-alcoholic solution of a volatile drug. F. Antibiotics : Drugs that inhibit the growth of or destroy bacteria and other microorganisms. An example is penicillin. G. Sulfonamides : Drugs that inhibit the growth of or destroy bacteria, particularly the coccus form. One example is sulfisoxazole. H. Antimalarials (plasmodicides) : Drugs that prevent or cure malaria; for example, chloroquine phosphate. I. Anti-inflammatories : These drugs suppress local inflammatory reactions. An example is hydrocortisone ointment, 1 percent, used for some eye inflammatory conditions (ophthalmia). J. Antifungals : These are drugs that check the growth of fungi. An example for external use (local application) is fungicidal foot powder. A recently developed antibiotic drug for oral administration in systemic treatment of fungus diseases of the skin is griseofulvin. K. Antihistamines : These are drugs that counteract the effects of histamine. The release of abnormal amounts of histamine into body tissues is associated with acute allergic and hypersensitivity reactions. An example of an antihistamine is diphenhydramine hydrochloride. L. Antiparasitics : Antiparasitics are used to eliminate skin infestation with mites. Examples for external use are gamma benzene hydrochloride ointment or lotion.
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