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Ready for Review Pharmacology is the study of the properties (characteristics) and effects of drugs and medications on the body. Drugs or medications are chemical agents used in the diagnosis, treatment, and prevention of disease. They have intended effects, unintended effects, and may have untoward effects (those that can be harmful to the patient). There are indications and contraindications for each medication. Indications are the therapeutic uses for a particular medication. Contraindications are cases in which you should not give a patient medication. As an AEMT you must be familiar with the various names of drugs (trade, generic, chemical, official), the sources of drugs, their classification, and sources where information on drugs may be obtained. The manufacture of pharmaceuticals in most countries is regulated to protect consumers. For example, standardized manufacturing is required for uniform strength and purity. The Controlled Substances Act of 1970 is comprehensive legislation dealing with narcotic and nonnarcotic drugs that have a potential for abuse and consists of five categories or schedules according to abuse potential. Schedule I represents the highest abuse potential and Schedule V is the lowest. Drugs must go through an approval process that includes animal studies and clinical trials in humans before being approved for distribution. The Food and Drug Administration (FDA) classifies newly approved drugs by several categories. There are special considerations for certain groups of patients when administering medications: geriatric, pediatric, and pregnant patients. With pregnant patients, the health of the mother is the priority in emergency situations. FDA Categories A, B, C, D, and X rate risk to the fetus, with Category X representing the greatest risk. There are several medication concerns related to geriatric patients. Effects of a medication may be delayed. Geriatric patients often take several medications, making drug interaction possible. Alterations in mental status can lead to overdosing or underdosing. As an AEMT, you are held responsible for safe and therapeutically effective drug administration. This includes legal, moral, and ethical considerations. Drugs are grouped into classifications based on their effect on a body system, by their effect on a system, or their mechanism of action (how they create the effect). To understand the effects drugs have on the body, you must have an understanding of the nervous system. The sympathetic nervous system is responsible for the body’s response to shock and stress (“fight or flight”). The parasympathetic nervous system relaxes the body, controlling automatic functions during nonstressful times (“rest and relax”). Adrenergic receptors cause a response in the target organ and are grouped as alpha-1, alpha-2, beta-1, and beta-2. Some medications stimulate alpha and beta receptors, whereas others may block specific receptors. Drugs that produce the same effects as sympathetic nervous system hormones are sympathomimetics. Medications that have the opposite effect are sympatholytics. Agonists aid or increase effects. Antagonists antagonize or fight the effects of another substance. Beta blockers are used to control blood pressure in some patients and heart rhythm disturbances in others. Beta blockers work by filling a portion of the beta receptor sites to prevent binding by beta stimulators that occur naturally in the body and can be introduced as a medication. Agonists to the parasympathetic nervous system are known as parasympathomimetics, and antagonists are known as parasympatholytics. One of the most commonly used parasympatholytics is the drug atropine that is used for symptomatic bradycardia and exposure to organophosphates and certain chemical nerve agents. Analgesics include medications that relieve pain. The most common class of medications used for analgesia in the prehospital setting comprises the opioid agonists. Opioid antagonists reverse the effects of opioid drugs. Opioid agonistantagonists have agonistic and antagonistic properties. They are often preferred because they can decrease pain but do not diminish the function of the respiratory system or lead to dependence or addiction. Sedative-hypnotics do what they suggest: sedate and produce hypnosis. They are preferred for invasive procedures. Drugs that create sedation and hypnosis include benzodiazepines, barbiturates, opioid agonists, and nonbarbiturate hypnotics. Stimulants excite the central nervous system, while depressants slow brain activity. Drugs that affect the cardiac system may affect heart rate, force of contraction, or velocity of conduction through the heart. Cardiac glycosides, antiarrhythmics, and antihypertensive medications are included in this group. Antihypertensive medications include diuretics, vasodilator medications, ACE inhibitors, and calcium channel blockers. Certain medications prevent or minimize the effects of thrombi. These include antiplatelet agents, anticoagulants, and fibrinolytics. Drugs that affect the respiratory system include oxygen, over-the-counter decongestants, bronchodilators, and xanthines. Drugs come in many different forms, including solid, liquid, inhaled, topical, transcutaneous, gels, and gases. Liquid intravenous medications are some of the most common medications in the prehospital setting. You should also know the various routes of medication administration and which routes are used for the drugs you may administer in the prehospital setting. Routes include enteral and parenteral. Enteral drugs are those that are administered along any portion of the gastrointestinal tract, including the oral and rectal routes. Parenteral drugs are those that are administered through any route other than the gastrointestinal tract and include intravenous (IV), intraosseous (IO), subcutaneous (SC), intramuscular (IM), sublingual (SL), buccal, transcutaneous, intranasal, and inhalation. Once drugs are administered, they go through four stages: absorption, distribution, metabolism, and excretion. Pharmacokinetics is the study of the metabolism and action of drugs with particular emphasis on the time required for absorption, duration of action, distribution in the body, and method of excretion. Pharmacodynamics is the way in which a medication produces the response we intended, also known as the mechanism of action. It also encompasses the factors that may alter the intended response and any side effects or unexpected effects. Factors that alter drug response include age, body mass, sex, environmental conditions, time of administration, genetic factors, and psychological factors. Responses beyond the desired effect are side effects and may occur even when a medication is administered properly. Unpredictable responses may occur when a medication is administered. These include allergic reaction, serum sickness, and idiosyncratic reaction. Other effects that may occur include cumulative effect, summation, potentiation, drug dependence, and drug interaction. Overall, it is important to learn as much as you can about the drugs you may be allowed to administer in your area. Carry a pharmacologic reference to look up drugs that may be unfamiliar. You should also be aware of proper drug storage and security. Follow local protocols for drug administration, and review pharmacology often.