When studying pharmacology, learning drugs by class is far more efficient than learning drugs individually. The main concept to understand is that drugs can be assigned two different types of drug classes. Pharmacologic and/or therapeutic.
When drugs are categorized by pharmacologic class, they are classified by how they exert their action in the body. When drugs are categorized by therapeutic class, they are classified by the intended effect.
For example, metoprolol is in the pharmacologic class of beta blockers. Beta blockers exert their action by blocking conduction at the heart’s AV node, which slows the heart rate, reduces cardiac output and therefore reduces blood pressure. When you know what beta blockers do in the body, then you can understand what will happen physiologically and what adverse effects you might watch for, such as bradycardia and hypotension.
Metoprolol is also classified therapeutically as an antihypertensive and an antianginal. In other words, its intended effects are to lower blood pressure and decrease or prevent angina. Understanding the therapeutic classification helps you understand why a patient is receiving a drug and what goal outcomes you will monitor your patient for. In the case of metoprolol, you would monitor your patient for a decrease in angina episodes or a systolic blood pressure below a specific MD-defined parameter.
Note that drugs will typically have one pharmacologic class, but sometimes more than one therapeutic class simply because they provide multiple therapeutic benefits. For example, diazepam, which is in the pharmacologic class of benzodiazepines, is also classified therapeutically as an anticonvulsant, an antianxiety agent, a sedative/hypnotic and a skeletal muscle relaxant.
Some drugs, such as propofol, tend to be referred to only by their therapeutic class instead of a pharmacologic class. For example, if you look up the medication propofol in your Davis Drug Guide, it only shows a therapeutic class. In cases like this it is often because we don’t fully understand the drug’s mechanism of action. In other words, we may not know exactly how it works, but we know what the therapeutic effect is.
As you are studying pharmacology, pay careful attention to the drug’s classification. When you focus on learning key characteristics of a drug class, you won’t have to memorize such a vast number of individual medications.
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