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Pharmacology

Peter Bechtel

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TEST TAKING TIPS

Test Taking Tips

The most commonly tested mechanism of actions of drugs are succinylcholine (vs other paralytics), imatinib, fluoroquinolones, warfarin, and corticosteroids. Don't over-memorize intricate details of exotic drug classes.

MECHANICS

What are some basic drug properties?

  • Absorption, distribution, metabolism, elimination

What is first-order kinetics?

  • Drug dose determines quantity eliminated (dose-dependent elimination)

What is zero-order kinetics?

  • Also known as Hoffman elimination: constant drug quantity eliminated per unit time

What is the primary role of the P450 system?

  • Primary drug oxidizers

What are some of the inducers of the P450 system?

  • Cigarette smoke, phenobarbital, rifampin, ethanol, INH, phenytoin, etc

What are some of the inhibitors of the P450 system?

  • Grapefruit, erythromycin, nelfinavir, itraconazole, etc

FIGURE 5-1.

Drug administration by continuous intravenous infusion (upper panel) or intermittent intravenous bolus (lower panel). Attainment of steady-state plasma concentration (Cpss) occurs after 3 to 5 half-lives, regardless of the dosing regimen. Peak and trough fluctuations around Cpss are aimed to each be within the therapeutic range (therapeutic but subtoxic plasma levels). (Reproduced from Hall JB, Schmidt GA, Wood LDH. Principles of Critical Care. 3rd ed. http://www.accessmedicine.com. Copyright © The McGraw-Hill Companies, Inc. All rights reserved.)

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What is half-life of a drug?

  • Purpose of dosing by half-life is to achieve steady-state concentration. Typical drugs reach steady state after 5 half-lives

What is a Phase I reaction?

  • Nonsynthetic reaction, for example, oxidation/reduction, NOT conjugation

What is a Phase II reaction?

  • Synthetic reaction, for example, conjugation, methylation, sulfation, etc

GASTROINTESTINAL

ESOPHAGUS

What are some treatments for achalasia?

  • Calcium channel blockers, long-acting nitrates, botulinum toxin injections

What is the management for esophageal varices bleeding?

  • Vasopressin (splanchnic vasoconstrictor at V1 receptors, increases factor VIII and VWF via extrarenal V2 receptors). Propanolol/Nadolol (preventative role; inhibits B2 adrenergic splanchnic vasodilation). Nitrates (reduce portal venous pressure)

What are some treatment options for reflux disease?

  • Selective H2 blockers (cimetidine, ranitidine, etc) = 24-hour acid reduction by 70%.

  • Proton pump inhibitors (pantoprazole, omeprazole, etc) = 10% rebound hyperacidity after discontinuing due to hypergastrinemia

STOMACH

What are the D2 agonists motility agents and how do they work?

  • Domperidone and metoclopramide, they increase lower esophageal sphincter (LES) tone, increase antrum contraction, increase small bowel peristalsis (beware of extrapyramidal symptoms ...

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