Chapter 206: Antimicrobials

INTRODUCTION

Adverse effects associated with antimicrobials occur primarily in three circumstances: side effects with therapeutic dosing, subacute to chronic effects from sustained therapeutic use, and acute toxicity resulting from excessive dosing. Side effects can be immunologic (allergic) or nonimmunologic (pharmacologic or idiosyncratic) in nature. Antibiotics cause more reported allergic reactions than other drugs, possibly due to their high frequency of use often in a repeated and interrupted fashion. Sometimes a diluent or other chemical constituent in the formulation of a drug causes the adverse effect.

Most patients who sustain an acute antimicrobial overdose remain asymptomatic, and observation is generally all that is required. Measurement of drug levels is neither helpful nor readily available to affect management but may be confirmatory. Levels are available for several antibiotics such as chloroquine, isoniazid, and quinine. Ancillary testing should be based on the substance ingested and the clinical condition of the patient, such as methemoglobin concentrations for patients with dapsone or chloroquine toxicity.¹ Some antimicrobials are associated with specific, significant toxicities following an acute ingestion and may require directed therapy (Table 206-1).

Consider GI decontamination for patients suspected of ingesting a toxic amount of a potentially dangerous antimicrobial agent. Single-dose activated charcoal without sorbitol given orally or via nasogastric tube is most beneficial within 1 hour of the ingestion.^2,3 Multidose activated charcoal is indicated in symptomatic patients who have ingested dapsone or quinine.⁴ Hemodialysis or hemoperfusion is effective at reducing concentrations of dapsone,^5,6 chloramphenicol,⁷ cefepime,^8,9 and possibly pentamidine.¹⁰

Ask women of childbearing age about pregnancy and lactation when prescribing antimicrobials. LactMed is a National Library of Medicine and National Institutes of Health database of drugs that describes maternal and infant levels of drugs and effects on breastfed infants and on lactation. Effective June 30, 2015, the U.S. Food and Drug Administration published the Pregnancy and Lactation Labeling Rule, which removed pregnancy letter categories (A, B, C, D, and X) and allows for considerations of risk and benefit when prescribing medication to pregnant and nursing women. ...