4-Methoxymethamphetamine (PMMA, para-Methoxymethamphetamine) is a stimulant and psychedelic drug closely related to the amphetamine-class serotonergic drug para-methoxyamphetamine (PMA). Little is known about the pharmacological properties, metabolism, and toxicity of 4-Methoxymethamphetamine. Because of its structural similarity to para-methoxyamphetamine, which has known toxicity in humans, it is thought to have considerable potential to cause harmful side effects or death in overdose. In the early 2010s, a number of deaths in users of the drug MDMA were linked to misrepresented tablets and capsules of 4-Methoxymethamphetamine. In 2010–2013, a cluster of 29 fatal poisonings related to the toxic designer drug 4-Methoxymethamphetamine was revealed in Norway. The toxicity of PMMA is regarded as substantially higher than for amphetamine, methamphetamine, and MDMA, as indicated by 131 fatal and 31 nonfatal poisonings associated with the abuse of 4-Methoxymethamphetamine worldwide. The toxicity of 4-Methoxymethamphetamine is positively correlated with the 4-Methoxymethamphetamine dose and the blood drug level, but the existing literature indicates that certain human subjects may have an increased risk of 4-Methoxymethamphetamine toxicity. 4-Methoxymethamphetamine, like PMA most likely acts as a selective serotonin releasing agent (SSRA) with weak effects on dopamine and norepinephrine transporters. However, relative to MDMA, it is considerably less effective as a serotonin releaser with properties more akin to a reuptake inhibitor in comparison. It evokes robust hyperthermia while producing only modest hyperactivity and serotonergic neurotoxicity, substantially lower than that caused by MDMA.

4-Methoxyamphetamine (Para-methoxyamphetamine, PMA) is a synthetic drug chemically similar to the recreational drug 3,4-methylenedioxymethamphetamine (MDMA or "ecstasy") and often replaces MDMA in tablets. Numerous cases of intoxication have been documented and fatal cases involving PMA have been described. PMA induces toxicity at lower doses than MDMA. Clinical symptoms specific to PMA poisoning include life-threatening hyperthermia, breathing difficulties, tachycardia, rhabdomyolysis, and acute renal failure. In the scarce studies conducted in laboratory animals, PMA has shown cardiovascular alterations in dogs, hyperthermia on a high ambient temperature, hallucinogen properties, and disruption of operant behavior in rats. A slight motor activity stimulation, lower than that induced by MDMA, has also been reported. The effects of PMA on brain neurotransmission are similar to those of MDMA, thus, PMA increases serotonin (5-hydroxytryptophan or 5-HT) release from the synaptic terminal and blocks its reuptake; it also acts upon noradrenergic and dopaminergic terminals but in a lesser proportion, and can also delay the metabolism of these monoamines by inhibition of monoamine oxidase (MAO)