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Pharmacology for techniciansPTCB Exam Prep
May 16, 2020
What is a "mechanism of action"?
Mechanism of action is how a drug works. All drugs produce the desired therapeutic effect. The mechanism of action explains how a drug achieves these desired effects.
Some drugs have more than one mechanism of action. Instead, they may produce therapeutic effects through several complementary mechanisms. However, most drugs have only one mechanism of action – many of which are listed in the table below.
As part of the PTCB exam, candidates are asked some of the most common questions about the mechanism of action test. There is now one for the 2020 curriculum40% weightPharmacological issues – MOAs play an important role in this.
It takes time to become familiar with the many different classes of drugs.
Certain classes of drugs depict the same mechanism of action. For example:
- ACE-HemmerBlocks angiotensin-converting enzyme.
- beta blockersIt works by blocking beta adrenergic receptors.
- PDE5 inhibitorBlocks phosphodiesterase type 5 enzymes.
There are many other classes of drugs whose mechanisms of action are unknown.
For example statins fromIt inhibits HMG-CoA reductase; Rate-limiting enzyme in the mevalonate pathway for cholesterol production.
How loop diuretics workthey block sodium+/K+/2Cl–fellow carrierProteins in the ascending limb of the loop of Henle. The loop of Henle is the U-shaped tube in the kidney that is involved in draining urine from the body.
Below we review the top 20 drug classes and briefly summarize their mechanisms of action.
Mechanism of Action – Top 20
| drug/drug class | Mechanism |
| Statinsatorvastatin and pravastatin | Statins work by inhibiting HMG-CoA reductase, the rate-limiting enzyme in the mevalonate pathway for cholesterol production. |
| beta blockersMetoprolol Bisoprolol Pindolol | Beta-1 adrenergic receptors are found in the heart. Beta-2 adrenergic receptors are found in the lungs. Memory Tools: Beta-1, 1 heart; Beta-2, 2 lungs! Some β-blockers are cardioselective, reducing the contractility and conduction velocity of the heart. This eases the work of the heart and eases the need for oxygen. Beta-blockers can also prolong the resistance period of the AV node, making these drugs effective in treating abnormal heart rhythms. |
| Beta-2-FighterSalbutamol Salmeterol | Beta-2 agonists are used to treat asthma and chronic obstructive pulmonary disease. By stimulating (or “exciting”) beta-2 receptors in the lungs, beta-2 agonists cause smooth muscle to relax – making it easier to improve airflow in the lungs. |
| CorticosteroidsDexamethasone Prednisolone | Corticosteroids bind to glucocorticoid receptors on surface cells, which then travel to the nucleus to alter gene expression. Corticosteroids upregulate anti-inflammatory genes and downregulate pro-inflammatory genes. |
| TetracyclinesMinocycline Doxycycline | Proteins are essential for the survival of cells, including bacterial cells. Tetracyclines work by inhibiting protein synthesis in bacterial cells. |
| ACE-HemmerCaptopril Lisinopril Ramipril | ACE inhibitors block angiotensin-converting enzyme, which normally converts angiotensin I to angiotensin II. Angiotensin II is responsible for actions such as vasoconstriction (narrowing of blood vessels and an increase in blood pressure) and the release of the hormone aldosterone, which further increases blood pressure. ACE inhibitors block this action of angiotensin II and are therefore used as antihypertensive drugs. |
| NSAIDs Naproxen Ibuprofen Etoricoxib | NSAIDs are non-steroidal anti-inflammatory drugs. They work by inhibiting cyclooxygenase or COX. There are two types of COX: COX-1 and COX-2. The therapeutic effect of NSAIDs is based on the inhibition of COX-2 - the reduction of inflammation. Therefore, NSAIDs are used to treat mild to moderate pain and pain associated with inflammation. Aspirin also works by inhibiting COX. |
| Opioids Codeine Dihydrocodeine Tramadol Morphine | Opioids are used to treat pain. They act as mu opioid receptor agonists. |
| AntimykotikaKetoconazole Nystatin Clotrimazole | Azole antifungals work by attacking ergosterol in the cell membrane of the fungus. By targeting ergosterol, it interferes with cell membrane synthesis, cell growth and cell reproduction, thereby destroying fungal cells. |
| PenicillinBenzylpenicillin, Flucloxacillin, Ampicillin, Amoxicillin | Penicillin inhibits the enzyme responsible for joining basic elements in the bacterial cell wall. By weakening bacterial cell walls, penicillin causes these cells to swell, rupture, and eventually die. The antibacterial activity of penicillins is due to the fact that they contain a β-lactam ring. Their chemical structure is a four-sided square ring. Another class of drugs -- called cephalosporins -- also contain a beta-lactam ring and work in the same way. Examples include cefazolin, ceftriaxone, cefdinir and cefoperazone. |
| proton pump inhibitorsLansoprazole Omeprazole Pantoprazole | PPIs are used to treat conditions caused by excess stomach acid. PPIs inhibit the production of stomach acid by blocking the "proton pump" that sends hydrogen ions into the stomach. PPIs bind irreversibly to the H+/K+-ATPase (also called proton pump) in parietal cells. |
| FluoroquinoloneCiprofloxacin Moxifloxacin | Fluoroquinolones are antibacterial drugs that work by inhibiting DNA synthesis. Since the cells cannot multiply, productivity is reduced, allowing the body to fight the infection. |
| BenzodiazepineDiazepam Midazolam Nitrazepam | Benzodiazepines are used to treat anxiety, seizures, induce anesthesia, and insomnia. They work by increasing the binding of the neurotransmitter GABA to GABA A receptors. Once bound, it exerts an "inhibitory" effect on the synaptic transmission of neurons, resulting in a reduction of anxiety, sleepiness, as well as a sedative and anticonvulsant effect. |
| AntipsychoticsHaloperidol Chlorpromazin Risperidon Clozapin | Antipsychotic drugs work through a complex array of mechanisms, but one of the most common is blocking postsynaptic D2 receptors. D2 receptors are "dopaminergic" receptors that affect dopamine levels. Blockade of D2 is one of the main ways that antipsychotic drugs reduce psychotic symptoms in affected patients. |
| SSRIs Fluoxetine, Paroxetine, Sertraline | SSRIs are "Selective Serotonin Reuptake Inhibitors". Antipsychotics work on dopamine receptors, while SSRIs work on serotonin levels. Specifically, SSRIs inhibit the reuptake of neurons in neuronal cells. This means there is more serotonin between neurons to increase neurotransmission. |
| AntihistaminesCetirizin Loratadin Fexofenadin Chlorpheniramin | These 4 drugs are histamine H1 antagonists. H1 antagonism prevents histamine release from mast cell granules. Histamine is responsible for the hypersensitivity phenomenon. Therefore, these drugs are used to treat allergies, hay fever, itching and hives. |
| AntihistaminesRanitidine | There is also an H2 receptor that reduces stomach acid production once it is blocked (or "antagonized"). For this reason, ranitidine is used to treat stomach ulcers, indigestion, and GERD. |
| Heparin | To form a clot you need thrombin and factor Xa. two key elements in the thrombus pathway. Heparin inactivates factor Xa and thrombin. There are also low molecular weight heparins and these drugs preferentially inhibit factor Xa. Examples include enoxaparin and dalteparin. |
| Warfarin | Warfarin is also used as an anticoagulant drug. However, warfarin works by inhibiting epoxide vitamin K reductase, thereby preventing the reactivation of vitamin K and the synthesis of procoagulant factors. |
| metformin | Metformin is used to treat type 2 diabetes. It works by increasing the sensitivity (or 'response') to insulin. This means, for example, that it inhibits glucose production in the liver, increases glucose uptake by skeletal muscle and inhibits glucose uptake in the gut. Together, this helps lower blood sugar levels. |
If you want to test your knowledge of pharmacology for a technician, we have a module (10 modules) on the subject andHundreds of PTCB practice testsattempt. Be sure to check back with the PTCB Exam Prep Blog soon for more great content on how to ace your next pharmacy exam!
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FAQs
What are the main mechanisms of drugs action? ›
In pharmacology, the term mechanism of action (MOA) refers to the specific biochemical interaction through which a drug substance produces its pharmacological effect. A mechanism of action usually includes mention of the specific molecular targets to which the drug binds, such as an enzyme or receptor.
What are the four mechanisms types of drugs? ›Antimicrobial resistance mechanisms fall into four main categories: (1) limiting uptake of a drug; (2) modifying a drug target; (3) inactivating a drug; (4) active drug efflux.
What are the five main actions of drugs? ›- Reversibility.
- Affinity and Intrinsic Activity.
- Potency, Efficacy, and Effectiveness.
In short, interactions between drugs can be classified as pharmacokinetic and pharmacodynamic, Of the former, the subdivisions would naturally have to include absorption, distribution, metabolism and elimination.
What are 3 mechanisms of drug drug interactions? ›Mechanisms of Drug Interactions I: Absorption, Metabolism, and Excretion.
What is the most common transport mechanism of most drugs? ›The most common mechanism of absorption for drugs is passive diffusion.
What is the mechanism of action of Tylenol? ›Mechanism of Action
Regardless, the reduction of the COX pathway activity by acetaminophen is thought to inhibit the synthesis of prostaglandins in the central nervous system, leading to its analgesic and antipyretic effects.
The mechanisms of pharmacokinetic interactions involve drug metabolizing enzymes, drug transporters and orphan nuclear receptors that regulate at the transcriptional level the expression of enzymes and transporters.
What are the 7 rules of drugs? ›- Medication Administration.
- Right Individual.
- Right Medication.
- Right Dose.
- Right Time.
- Right Route.
- Right Documentation.
- Right Response.
Specificity of drug action relates to the number of different mechanisms involved. Examples of specific drugs include atropine (a muscarinic receptor antagonist), salbutamol (a β 2-adrenoceptor agonist), and cimetidine (an H 2-receptor antagonist).
What are the types of drug action? ›
- Agonists – they stimulate and activate the receptors.
- Antagonists – they disable the agonists from stimulating the receptors.
- Intravenous Route. This directly administers the medications to the systemic circulation. ...
- Intramuscular Route. ...
- Subcutaneous Route.
- Drug-drug interaction: A reaction between two (or more) drugs.
- Drug-food interaction: A reaction between a drug and a food or beverage.
- Drug-condition interaction: A reaction that occurs when taking a drug while having a certain medical condition.
Usually, tolerance develops because metabolism of the drug speeds up (often because the liver enzymes involved in metabolizing drugs become more active) and because the number of sites (cell receptors) that the drug attaches to or the strength of the bond (affinity) between the receptor and drug decreases (see ...
What are the 6 transport mechanisms? ›The mechanisms of drug absorption are, in order of their importance, (1) passive diffusion, (2) convective transport, (3) active transport, (4) facilitated transport, (5) ion-pair transport, and (6) endocytosis (pinocytosis).
What are 4 factors that affect absorption of a drug? ›- physicochemical properties (e.g. solubility)
- drug formulation (e.g. tablets, capsules, solutions)
- the route of administration (e.g. oral, buccal, sublingual, rectal, parenteral, topical, or inhaled)
- the rate of gastric emptying.
There are four types of transport mechanisms in a cell. These are simple diffusion, facilitated diffusion, primary active transport and secondary active transport.
What is the mechanism of action of ibuprofen? ›The main mechanism of action of ibuprofen is the non-selective, reversible inhibition of the cyclooxygenase enzymes COX-1 and COX-2 (coded for by PTGS1 and PTGS2, respectively; Fig. 2) [1].
How does ibuprofen work? ›How does ibuprofen work? Ibuprofen works on one of the chemical pathways for pain. It reduces the ability of your body to make prostaglandins — chemicals that promote pain, inflammation and fever. With fewer prostaglandins in your body, fever eases, and pain and inflammation is reduced.
How does oxycodone work? ›How does oxycodone work? Oxycodone works directly on opioid receptors in the central nervous system and reduces feelings of pain by interrupting the way nerves signal pain between the brain and the body.
What are the six drug rights? ›
6 Rights of Medication Administration
These 6 rights include the right patient, medication, dose, time, route and documentation. Futhermore, nurses are also urged to do the three checks; checking the MAR, checking while drawing up medication and checking again at bedside.
- depressants – slow down the function of the central nervous system.
- hallucinogens – affect your senses and change the way you see, hear, taste, smell or feel things.
- stimulants – speed up the function of the central nervous system.
- Physical antagonists.
- Chemical antagonists.
- Physiological antagonists.
- Pharmacological antagonists.
- Allosteric antagonists.
- Central nervous system depressants.
- Central nervous system stimulants.
- Opiates and Opiodes.
- Hallucinogens.
- Marijuana.
In medicine, a term used to describe how a drug or other substance produces an effect in the body. For example, a drug's mechanism of action could be how it affects a specific target in a cell, such as an enzyme, or a cell function, such as cell growth.
What are the main functions of drugs? ›Drugs are substances that change a person's mental or physical state. They can affect the way your brain works, how you feel and behave, your understanding and your senses. This makes them unpredictable and dangerous, especially for young people. The effects of drugs are different for each person and drug.
What schedule drug is Xanax? ›Schedule IV Controlled Substances
Examples of Schedule IV substances include: alprazolam (Xanax®), carisoprodol (Soma®), clonazepam (Klonopin®), clorazepate (Tranxene®), diazepam (Valium®), lorazepam (Ativan®), midazolam (Versed®), temazepam (Restoril®), and triazolam (Halcion®).
Schedule II drugs include certain narcotics, stimulants, and depressant drugs. Some examples are morphine, cocaine, oxycodone (OxyContin®), , methylphenidate (Ritalin®), and dextroamphetamine (Dexedrine®).
What is a drug mode of action vs mechanism? ›In pharmacology and biochemistry, mode of action (MoA) describes a functional or anatomical change, resulting from the exposure of a living organism to a substance. In comparison, a mechanism of action (MOA) describes such changes at the molecular level.
What is mechanism of action drug classification? ›Drugs are divided into 6 classes, according to their action on: 1) signal-transduction systems, 2) other components of plasmatic membranes, 3) intracellularly, 4) gene therapy, 5) extracellularly, 6) invasive agents.
What is a drug mode of action vs mechanism of action? ›
Mode of action usually refers to the functional or anatomical changes at a cellular level induced by exposure to a substance, whereas Mechanism of Action includes specific targets or pathways modulated by the compound.
What are the four roles of medicine? ›The Hastings Center Goals of Medicine project articulated four goals: (1) the prevention of disease and injury and the promotion and maintenance of health; (2) the relief of pain and suffering caused by maladies; (3) the care and cure of those with a malady and the care of those who cannot be cured; and (4) the ...
What releases the most dopamine? ›Crystal meth releases more dopamine in the brain compared to any other drug. Dopamine is a brain neurotransmitter that serves a number of functions, including the feeling of pleasure.
What are the three important properties of any drug? ›The most important properties of an ideal drug are: effectiveness, safety, and selectivity.