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Sglt2 inhibitor drug causing fourniers

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SGLT2 inhibitor Fournier gangrene

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Here is a complete summary of SGLT2 inhibitors and Fournier's gangrene, drawn from multiple authoritative textbooks:

SGLT2 Inhibitors and Fournier's Gangrene

The Drug Class

All SGLT2 inhibitors carry this risk as a class effect. The approved agents in the US are:
  • Canagliflozin
  • Dapagliflozin
  • Empagliflozin
  • Ertugliflozin
No single agent is uniquely implicated - the FDA warning applies to the entire class.

What is Fournier's Gangrene?

Fournier's gangrene (also called necrotizing fasciitis of the perineum) is:
  • A severe, rapidly progressing necrotizing infection of the external genitalia, perineum, or perianal area
  • Polymicrobial in nature (mixed aerobic and anaerobic organisms)
  • Life-threatening without urgent surgical intervention
  • Dermatology 2-Volume Set, 5e

FDA Warning (2018)

In August 2018, the FDA released a safety communication based on 12 post-marketing cases of Fournier's gangrene associated with SGLT2 inhibitor use - a rare but serious adverse effect. This prompted labeling updates for all drugs in the class.
  • Fuster and Hurst's The Heart, 15th Edition

Mechanism / Why SGLT2 Inhibitors Cause This

SGLT2 inhibitors work by causing glycosuria (spilling glucose into the urine). This creates a glucose-rich perineal environment that:
  1. Promotes bacterial and fungal overgrowth in the genital/perineal area
  2. Increases susceptibility to urogenital infections (a well-known class effect)
  3. In predisposed patients (especially diabetics, immunocompromised), this can progress to deep-tissue necrotizing infection
The underlying diabetes itself is an independent risk factor for Fournier's gangrene, as is immunosuppression.
  • Katzung's Basic and Clinical Pharmacology, 16th Edition
  • Lippincott Illustrated Reviews: Pharmacology

Other Risk Factors That Compound the Risk

Risk FactorNotes
Diabetes mellitusIndependent predisposing condition
ImmunosuppressionReduces ability to fight infection
Poor perineal hygieneDirect risk factor
Combination with sulfonylurea/insulinIncreases hypoglycemia risk, worsens metabolic milieu

Management of Fournier's Gangrene

  1. Emergency surgical debridement - wide and extensive
  2. Prolonged systemic antibiotics (broad-spectrum, covering polymicrobial flora)
  3. Discontinue the SGLT2 inhibitor immediately
  4. Supportive care / ICU level management

Other Notable Adverse Effects of SGLT2 Inhibitors (for context)

  • Genital mycotic infections (most common; same glycosuria mechanism)
  • UTIs
  • Volume depletion / hypotension
  • DKA at near-normal glucose levels ("euglycemic DKA")
  • Bone fractures (canagliflozin)
  • Modest LDL increase (canagliflozin, empagliflozin: 4-8%)
  • Renal insufficiency (especially in CKD)
Key exam point: Fournier's gangrene with SGLT2 inhibitors is a class effect, not specific to one drug. The mnemonic to remember: glycosuria → perineal glucose → necrotizing infection. Patients should be counseled on perineal hygiene and to seek urgent care for any genital/perineal pain, swelling, or fever.

Stain of hsv

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Staining for HSV - Complete Summary

1. Tzanck Smear (Classic / Most Tested)

How it is done:
  • Scrape the base of a freshly ruptured vesicle
  • Stain with Giemsa or Wright's stain (Papanicolaou stain can also be used)
  • Examine microscopically for multinucleated giant cells (Tzanck cells)
What you see:
Tzanck smear - Positive Giemsa stain showing a giant multinucleated keratinocyte (Tzanck cell) surrounded by neutrophils. The large dark-blue multinucleated cell is characteristic of herpetic infection.
Giemsa-stained smear from a vesicle base showing a giant multinucleated keratinocyte (Tzanck cell). Compare its size with surrounding neutrophils.
  • Fitzpatrick's Dermatology, 5e

Key Points to Remember

FeatureDetail
Test nameTzanck smear / Tzanck test
Stains usedGiemsa (most common), Wright's, Papanicolaou
FindingMultinucleated giant cells (Tzanck cells) + intranuclear eosinophilic inclusions
SensitivityLow - positive in <40% of culture-proven cases; even lower (<30%) for mucosal swabs
Specificity problemCannot distinguish HSV from VZV - both cause identical Tzanck cell changes
SpecimenScraping from base of freshly ruptured vesicle

2. Direct Fluorescent Antibody (DFA) Staining

  • Stains lesion scrapings with fluorescent-labeled antibodies
  • More sensitive than Tzanck smear, but less sensitive than viral culture
  • Can be used as an alternative rapid test

3. Skin Biopsy (Histopathology)

On H&E or special stains, biopsy shows:
  • Enlarged, swollen epithelial cells that are often separated (ballooning degeneration)
  • Multinucleated cells
  • Intranuclear eosinophilic inclusion bodies (Cowdry type A inclusions)

4. Gold Standard: PCR + Viral Culture

MethodNotes
PCRMost sensitive; preferred for CNS/neonatal HSV; can type HSV-1 vs HSV-2
Viral cultureCytopathic effect visible in 48-96 hours; spin-amplified culture can give result in <24 hours; needed for antiviral sensitivity testing

Summary Hierarchy (Sensitivity)

PCR > Viral culture > DFA staining > Tzanck smear
Exam pearl: The Tzanck smear is positive in HSV and VZV - it does NOT differentiate between the two. For HSV-1 vs HSV-2 typing, PCR or culture is required. - Harrison's Principles of Internal Medicine, 22e
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