U01.05.038 Drug reactions—renal/genitourinary

Understanding renal and genitourinary drug reactions is crucial for identifying potential complications in patients. Here, we summarize the key drug reactions, their causal agents, and important notes to aid USMLE Step 1 preparation.

Common Drug Reactions

1. Fanconi Syndrome

Causal Agents:
- Cisplatin
- Ifosfamide
- Expired tetracyclines
- Tenofovir
Pathophysiology:
Impaired function of the renal proximal tubule, leading to loss of glucose, amino acids, phosphate, and bicarbonate in the urine.

2. Hemorrhagic Cystitis

Causal Agents:
- Cyclophosphamide
- Ifosfamide
Prevention:
Coadminister mesna, which binds toxic metabolites (acrolein) in the bladder.

3. Interstitial Nephritis

Causal Agents: Remember the 5 P’s:
1. Pee: Diuretics
2. Pain-free: NSAIDs
3. Penicillins and cephalosporins
4. PPIs (Proton Pump Inhibitors)
5. rifamPin
6. Sulfa drugs
Clinical Features:
Allergic-type reaction with fever, rash, eosinophilia, and renal impairment.

Summary Table: Renal/Genitourinary Drug Reactions

Reaction	Causal Agents	Notes
Fanconi Syndrome	Cisplatin, ifosfamide, expired tetracyclines, tenofovir	Proximal tubule dysfunction; leads to electrolyte and nutrient wasting.
Hemorrhagic Cystitis	Cyclophosphamide, ifosfamide	Prevent with mesna to neutralize toxic metabolites.
Interstitial Nephritis	Diuretics, NSAIDs, Penicillins, cephalosporins, PPIs, rifampin, sulfa drugs	Hypersensitivity reaction; 5 P’s mnemonic helps recall causative drugs.

Points to Remember

Fanconi Syndrome involves the renal proximal tubule and may be caused by expired medications.
Mesna is critical to prevent hemorrhagic cystitis when using cyclophosphamide or ifosfamide.
The mnemonic 5 P’s is a helpful tool to recall drugs associated with interstitial nephritis.
Understanding drug reactions is vital for anticipating complications and improving patient outcomes.

References

Kaplan USMLE Step 1 Lecture Notes: Pharmacology.
First Aid for the USMLE Step 1.