Can methylene blue be given for vasoplegia following Coronary Artery Bypass Grafting (CABG) in a patient taking Celexa (citalopram)?

Methylene Blue for Post-CABG Vasoplegia in Patients on Citalopram

Methylene blue can be given for vasoplegia following CABG in a patient taking citalopram (Celexa), but only if the citalopram is discontinued first and the patient is monitored intensively for serotonin syndrome, as the FDA explicitly contraindicates concurrent use of these medications. 1

Critical FDA Contraindication

• The FDA drug label for citalopram explicitly states: "Do not start citalopram tablets in a patient who is being treated with linezolid or intravenous methylene blue because there is an increased risk of serotonin syndrome." 1
• If methylene blue treatment is deemed essential for life-threatening vasoplegia, citalopram must be stopped promptly before methylene blue administration 1
• The patient requires monitoring for serotonin syndrome symptoms for 2 weeks or until 24 hours after the last methylene blue dose, whichever comes first 1
• Citalopram may only be resumed 24 hours after the last dose of methylene blue 1

Clinical Decision Algorithm

Step 1: Assess Severity of Vasoplegia

• First-line therapy for post-CABG vasoplegia remains norepinephrine (at doses up to 100 μg/min in adults), which demonstrates excellent survival rates with low ischemic complications 2
• Methylene blue should only be considered for refractory vasodilatory shock that fails to respond to conventional vasopressors 3, 4

Step 2: If Methylene Blue is Deemed Essential

• Immediately discontinue citalopram before administering methylene blue 1
• Consider alternative vasopressor strategies first, including vasopressin or hydroxocobalamin, which do not carry the serotonin syndrome risk 5
• Document that the potential benefits of methylene blue outweigh the risks of serotonin syndrome in this particular patient 1

Step 3: Methylene Blue Administration Protocol

• Standard dose: 2 mg/kg administered intravenously over 20 minutes for post-cardiac surgery vasoplegia 6
• Alternative dosing: 1-2 mg/kg over 3-5 minutes, with total cumulative dose not exceeding 7 mg/kg 3
• Expect clinical response (increased systemic vascular resistance and decreased norepinephrine requirements) within 1 hour in approximately 93% of patients 6

Step 4: Monitor for Serotonin Syndrome

• Serotonin syndrome symptoms include: mental status changes (agitation, hallucinations, delirium, coma), autonomic instability (tachycardia, labile blood pressure, diaphoresis, flushing, hyperthermia), neuromuscular symptoms (tremor, rigidity, myoclonus, hyperreflexia), seizures, and gastrointestinal symptoms 1
• Monitoring must continue for 2 weeks or 24 hours after the last methylene blue dose 1
• If serotonin syndrome develops, discontinue all serotonergic agents immediately and initiate supportive symptomatic treatment 1

Evidence for Methylene Blue in Post-CABG Vasoplegia

• Methylene blue acts as a nitric oxide synthase inhibitor and guanylate cyclase blocker, increasing systemic vascular resistance in vasodilatory shock 2, 7
• In a series of 54 patients with norepinephrine-refractory vasoplegia after cardiopulmonary bypass, methylene blue produced clinically relevant increases in systemic vascular resistance in 93% of patients, with only 5.6% mortality 6
• The American Heart Association notes that methylene blue responses may be mixed and effects can be transient, particularly in calcium channel blocker overdose contexts 2

Critical Pitfalls to Avoid

• Never administer methylene blue while the patient is actively taking citalopram or any SSRI - this is an absolute contraindication per FDA labeling 1
• Do not use methylene blue as first-line therapy; it is reserved for catecholamine-refractory vasoplegia only 3, 4, 7
• Be aware that methylene blue can cause anticholinergic toxicity (fever, mydriasis, anuria) independent of serotonin syndrome, particularly in renal failure 8
• The risk applies specifically to intravenous methylene blue at doses of 1-8 mg/kg; lower doses or non-intravenous routes have unclear risk but caution is still warranted 1

Alternative Approaches

• Vasopressin remains a viable alternative vasopressor without serotonin syndrome risk 5
• Hydroxocobalamin can be used in combination with other pressors for severe vasoplegia without the drug interaction concerns 5
• High-dose insulin therapy may be considered for cardiogenic components of shock 2
• VA-ECMO should be considered for refractory shock if available, with reported survival rates up to 77% 2