What medications can cause green urine?

Medications That Cause Green Urine

The most common medications causing green urine are methylene blue and propofol, both of which produce a benign, self-limited discoloration that resolves after drug discontinuation. 1, 2

Primary Causative Agents

Methylene Blue

• Methylene blue (0.5%-1.0%) is the most well-established cause of green urine discoloration, used primarily in gastrointestinal endoscopy for chromoendoscopy and detection of Barrett's esophagus 1
• The green hue develops because methylene blue stain persists for up to 24 hours until complete renal excretion occurs 1
• This discoloration also affects stool, giving it a green appearance 1
• Methylene blue is found in some traditional Chinese medicines and can cause unexpected green urine when patients don't disclose herbal supplement use 3
• This is a completely benign side effect with no nephrotoxic potential 1

Propofol

• Propofol causes green urine discoloration in less than 1% of cases, typically when clearance exceeds hepatic elimination and extrahepatic pathways predominate 4
• Green discoloration most commonly occurs with prolonged propofol infusions ≥24 hours (39% of cases), but can develop even after brief exposures of ≤3 hours (22% of cases) 5
• The discoloration may appear during propofol administration or up to ≥3 hours after discontinuation 5
• Duration is typically ≤24 hours after stopping propofol 5
• Propofol-associated green urine is never associated with worsening kidney function and is entirely benign 5, 4
• The actual chemical origin remains unknown despite liquid chromatography-mass spectrometry analysis 2

Other Medications Associated with Green Urine

Additional agents reported in the literature include: 6

• Amitriptyline (tricyclic antidepressant)
• Indomethacin (NSAID)
• Promethazine (antihistamine)
• Cimetidine (H2 blocker)
• Methocarbamol (muscle relaxant)
• Metoclopramide (antiemetic)

Clinical Approach

Key Diagnostic Steps

• Obtain a thorough medication history including over-the-counter drugs, herbal supplements, and traditional medicines 3
• Review recent anesthesia records for propofol use, particularly in ICU patients or those who recently underwent procedures 5, 4
• Check for recent endoscopic procedures where methylene blue chromoendoscopy may have been performed 1
• Simple laboratory analysis can identify methylene blue and avoid expensive unnecessary investigations 3

Important Differentiations

• Green urine from medications is benign and self-limited, requiring no intervention beyond reassurance 1, 5, 4
• Rule out pathological causes such as Pseudomonas urinary tract infections (which can produce green pigment pyocyanin)
• Distinguish from indigo carmine, another contrast dye used in endoscopy that is not absorbed and doesn't typically cause urine discoloration 1

Common Pitfalls

• Failing to ask about herbal or traditional medicine use, particularly those containing methylene blue 3
• Ordering extensive renal workup when the cause is benign medication effect 3
• Not recognizing delayed onset of propofol-associated discoloration that can occur hours after drug discontinuation 5
• Confusing green urine with the orange discoloration caused by rifampin and other rifamycins, which is a different phenomenon 7