Ketamine

Ketamine produces dose-dependent increases in heart rate and blood pressure. Pre-existing uncontrolled hypertension is an absolute contraindication due to risk of hypertensive crisis.

Severe heart failure, unstable angina, recent myocardial infarction, and aortic dissection are absolute contraindications due to ketamine's cardiovascular stimulation.

Co-administration with opioids (all classes), GHB/GBL, or alcohol is absolutely contraindicated due to synergistic respiratory depression and aspiration risk. Darke et al. 2021 found essentially all ketamine-related deaths involved polydrug toxicology.

Lahti et al. 2001 demonstrated that 70% of schizophrenic volunteers experienced exacerbation of positive symptoms at subanesthetic doses (0.1-0.5 mg/kg IV). Psychotic disorders including schizophrenia, schizoaffective disorder, and active psychosis are absolute contraindications.

Active liver disease or significant hepatic impairment increases risk of prolonged drug effects and ketamine-induced hepatotoxicity. Noppers et al. 2011 documented elevated LFTs in 50% of CRPS patients receiving repeated ketamine infusions.

Patients with interstitial cystitis, chronic bladder disease, or prior ketamine-related urinary symptoms face accelerated uropathy risk. Even limited exposure may worsen pre-existing conditions.

Hyperthyroidism and thyrotoxicosis increase vulnerability to ketamine's cardiovascular stimulation. Relative contraindication; controlled hypothyroidism is not a barrier.

Pregnancy is an absolute contraindication. Teratogenic potential is not well-characterized but NMDA receptors play critical roles in neurodevelopment, and precautionary exclusion is standard across clinical guidelines.