Basic Pharmacological Concepts and Calculations WHAT IS PHARMACOLOGY Pharmacology is the branch of science which deals with the characteristics and properties of drugs. Of particular interest are the actions and effects of these chemicals on the human body. Pharmacology can be broken down into: The study of drugs: involves pharmacotherapeutics which is defined as curing, treating or preventing disease and the alleviation of pain and suffering. The study of drugs includes drug abuse and toxicology. The study of the effects of drugs Pharmacodynamics: what the drug does to the body Pharmacokinetics: what the body does to the drug Drug: chemical substance that has actions on living tissues. Xenobiotic: any foreign substance taken into the body that may produce beneficial effects or they may be toxic. Toxicants: substances that produce adverse biological effects Ultimate toxicant: toxic metabolites of a xenobiotic Toxins: specific proteins produced by living organisms (mushroom toxin or tetanus toxin) that exhibit immediate (acute) effects. Poisons: toxicants that cause immediate death or illness when experienced in very small amounts. TYPES OF DRUGS Chemotherapeutics: antibiotics Pharmacodynamics: Agonists: drugs that occupy receptors and activate them Antagonists: drugs that occupy receptors but do not activate them. Antagonists block receptor activation by agonists. Other DRUG CLASSIFICATION Examples of classifications of drugs: Source: cannabinoids Chemical formula: xanthine derivatives Mode of action: muscle relaxants, antihistamines and diuretics Therapeutic use: antidepressants, antihypertensive and antiinflammatories. System acted upon: CNS depressants, respiratory stimulants Drug schedule: S4 (prescription), S7 (poison) or OTC (over the counter) Prototype: aspirin like analgesics Popularity: Australias top 10 prescribed drugs, by cost, by safety in pregnancy DOSAGE Dose: the amount of a substance administered at a given time (interval) Exposure does: the amount of xenobiotic (foreign compound) encountered in the environment. (Expressed as mgL, mgg or ppb) Absorbed does: the actual amount of the exposed dose that enters the body Administered dose: the quantity administered Total dose ADMINISTRATION Orally, under the tongue (sublingually where they diffuse into blood vessels), dermal (applied to skin), by injection which is subcutaneous (under skin), intravenous, intramuscular, into a joint (intraarticular) or into soft tissue. Additionally drugs can be administered rectally, vaginally, nasal, inhalation, ear, eye or implanted under the skin. PHARMACOKINETICS Pharmacokinetics describes what happens to an administered drug with the passage of time. It is a study of the factors affecting bioavailability and can be broken down into; absorption, distribution, metabolism an excretion (ADME). Pharmacokinetic factors are important in the determination of: Duration of action Size of dose Frequency of dosage Drugdrug interactions Drugfood interactions PROCESSES THAT ARE TARGETS FOR DRUGS Receptor activation, enzyme inhibition, ion channels and DNA transcription factors.