4F-MPH

structural heart disease, recent myocardial infarction, uncontrolled arrhythmias

Severe cardiovascular disease — including structural heart disease, recent myocardial infarction, and uncontrolled arrhythmias — is an absolute contraindication. 4F-MPH's catecholaminergic stimulation elevates cardiac workload. Given its 2–3× greater DAT/NET potency relative to methylphenidate, cardiovascular stress may be amplified at equivalent milligram doses.

Uncontrolled or poorly managed hypertension is a relative contraindication. 4F-MPH produces dose-dependent blood pressure elevation through NET blockade and subsequent noradrenergic potentiation. Individuals with pre-existing hypertension face compounded cardiovascular risk.

Seizure disorders are a relative contraindication. Stimulants may lower the seizure threshold, and this risk is compounded when 4F-MPH is combined with other seizure-threshold-lowering agents.

Anxiety disorders are a relative contraindication. 4F-MPH's potent NET blockade increases noradrenergic transmission, which can exacerbate anxiety. The non-fatal intoxication case (Papa 2019) demonstrated agitation and neuropsychiatric disturbance consistent with anxiety exacerbation.

A history of psychosis or bipolar disorder is a relative contraindication. Dopaminergic potentiation from DAT blockade can trigger psychotic symptoms or precipitate manic episodes. The non-fatal case required antipsychotic medication (promazine, quetiapine) upon discharge, consistent with stimulant-induced psychiatric disturbance.

Hepatic impairment is a relative contraindication. Methylphenidate is primarily metabolized by hepatic carboxylesterase 1 (CES1). If 4F-MPH follows the same pathway — as suggested by metabolic studies showing analogous de-esterification (Manier 2020) — impaired liver function could reduce clearance.

Pregnancy and lactation are relative contraindications by precautionary principle. No reproductive toxicity data exist for 4F-MPH in any species. The compound's potent catecholaminergic activity poses theoretical risks to fetal development.

Concurrent use of monoamine oxidase inhibitors (MAOIs) with 4F-MPH is contraindicated due to the risk of hypertensive crisis. MAOIs prevent enzymatic degradation of catecholamines while 4F-MPH blocks their reuptake at DAT and NET, producing compounded norepinephrine and dopamine accumulation. This is a class-level contraindication for all stimulants.

Pheochromocytoma is an absolute contraindication. These catecholamine-secreting tumors already produce dangerous catecholamine excess; adding a potent DAT/NET reuptake inhibitor compounds the risk of hypertensive crisis, stroke, or cardiac emergency.