We are proud to present Capsules Module 10: Concepts in Infectious Disease, now published on ALiEMU. Here is a summary of the key points from a stellar module by Drs. Meghan Groth and Paul Takamoto. When you’re finished, head over to the Capsules page for even more practical pharmacology for the EM provider.

Course Contributors

RoleTeam MemberBackground
AuthorsMeghan Groth, PharmD, BCPS @EMPharmgirlEmergency Medicine Pharmacist, UMass Memorial Medical Center
Paul Takamoto, PharmD @ptakpharmEmergency Medicine Pharmacist, University of California, San Francisco
PharmD ReviewersMichelle Hines, PharmD @mEDPharmDFood and Drug Administration
Zlatan Coralic, PharmD, BCPS @ZEDPharmEmergency Medicine Pharmacist, University of California, San Francisco
Expert ReviewerEmily Heil, PharmD, BCPS-AQ ID @emilylheilInfectious Disease Pharmacist, University of Maryland Medical Center
Associate EditorsEmily Wiener, PharmD @PharmdEMilyEmergency Medicine Pharmacist, Baltimore Washington Medical Center
Xander Miller @XanderBOSP4 Pharmacy Student, Northeastern University/Pharmacy Intern, Massachusetts General Hospital
Lead EditorBryan Hayes, PharmD, FAACT, FASHP @PharmERToxGuyEmergency Medicine Pharmacist, Massachusetts General Hospital

Foundational Concepts

CAPSULE: Antibiotic Selection
  • Consider the benefit and harm of any antimicrobial prior to initiating treatment.
  • The relevance of “bactericidal” versus “bacteriostatic” when selecting an antibiotic in the ED is unclear.
  • Be sure to distinguish whether a patient’s reported allergy is a true allergy, adverse effect, or intolerance.

Tailor Your Regimen to the Pharmokinetics

The minimum inhibitory concentration (MIC) is the lowest antibiotic concentration that can prevent bacterial growth, and antibiotics are either time- or concentration-dependent. Time-dependent antibiotics (e.g. beta-lactams) are most effective when the concentration is above the MIC for the longest time possible. Concentration-dependent antibiotics, however, kill most rapidly at higher doses, and effects can persist long after a dose is given. Fluoroquinolones are an example.

CAPSULE: Using Patient Culture Data
MICs for 2 different antibiotics should not be compared to one another. Rather, look at whether or not the microbiology report states “susceptible,” “intermediate,” or “resistant.”

Some antibiotics, including beta-lactams and vancomycin, can be dosed based on total body weight, even in obese patients (if normal renal function). If total body weight exceeds the ideal body weight by more than 20%, an adjusted dosing weight may be more appropriate. Independent of body weight, beta-lactams and vancomycin are 2 antibiotics that may require a loading dose in critically-ill patients.

CAPSULE: Vancomycin Loading Dose in Critically Ill Patients
A loading dose of vancomycin of 25-30 mg/kg may help avoid initial subtherapeutic trough levels, which have been associated with therapeutic failure.

Lastly, special consideration should be given to antibiotic dosing in the pediatric population and those with obesity. Medication absorption, volume of distribution, protein binding, hepatic metabolism, and renal elimination will vary based on age and size. Close monitoring for adverse reactions may be required in some of these patients.

What is the Capsules series?

ALiEMU Capsules is a free, online e-curriculum of high-quality, current, and practical pharmacology knowledge for the EM practitioner. About once a month a new course module is released, which has lessons to read about (or watch) and brief quizzes to complete. With each step, your personal dashboard will keep track of what you have completed. The Capsules series’ primary focus is bringing EM pharmacology education to the bedside. Our expert team distills complex pharmacology principles into easy-to-apply concepts. It’s our version of what-you-need-to-know as an EM practitioner.

Bryan D. Hayes, PharmD, DABAT, FAACT, FASHP

Bryan D. Hayes, PharmD, DABAT, FAACT, FASHP

Leadership Team, ALiEM
Creator and Lead Editor, Capsules and EM Pharm Pearls Series
Attending Pharmacist, EM and Toxicology, MGH
Associate Professor of EM, Division of Medical Toxicology, Harvard Medical School
Bryan D. Hayes, PharmD, DABAT, FAACT, FASHP


EM Pharmacist & Toxicologist @MassGeneralEM | Asst Prof @HarvardMed/@EMRES_MGHBWH | @ALiEMteam leadership | Capsules creator, ALiEMU | President, ABAT | #FOAMed