Ephylone has been linked to numerous overdoses and deaths. It is strongly discouraged to use this substance in high doses, multiple times in a row, or in combination with other substances known to increase the risk of psychosis or serotonin syndrome.

N-Ethylpentylone is a novel stimulant-entactogen substance of the cathinone class. Ephylone is chemically related to pentylone and belongs to a group of compounds known as the substituted cathinones. Little is known about its pharmacology, although it likely produces its effects by increasing levels of serotonin, dopamine, and norepinephrine in the brain.

Ephylone was developed in the 1960s as a central nervous system stimulant, although it never became marketed. Reports of recreational use first appeared in late 2015. Since then, its prevalence has steadily risen, particularly at dance music festivals where it appears as an adulterant or counterfeit for MDMA. Ephylone has been linked to numerous hospitalizations and overdose deaths. User reports indicate that ephylone produces a mixture of classic stimulant and entactogenic effects resembling those of MDMA, methylone and cocaine. Unlike similar substances, however, ephylone is reported to be very long lasting when taken in larger doses.

Excerpt from psychonautwiki.org:
https://psychonautwiki.org/wiki/Ephylone

If it isn't MDMA, then it's very likely to be a new drug called n-ethylpentylone. Testing at festivals has shown that around one quarter of the drugs that people believe to be MDMA (ecstasy) are not as expected. The most most common substitutions for MDMA come from the cathinone family of stimulants ("bath salts") and the most common cathinone seen this year is n-ethylpentylone. It was first seen in the USA in 2016. Testing at events this summer is showing it to be much more available now, often found as white or coloured powder that looks exactly the same as samples confirmed to be MDMA. This stimulant produces some of the same effects as MDMA, but users have described the experience as "seedy", "cracky", and much less pleasant.

Physical effects can include raised pulse and blood pressure, high body temperature, convulsions, acidosis, and rapid muscle breakdown. Psychological effects include agitation, paranoia, compulsion to redose, difficulty sleeping for up to 36 hours, and temporary psychosis.

As this drug is so new, little can be said about the health risks of long-term use. We also do not know much about risks of mixing this with other substances but like other cathinones it should not be taken with alcohol.

A particular risk is that n-ethylpentylone is significantly more potent than MDMA so it is very easy to take too much. A common dose for MDMA is around 100 milligrams, whereas a dose for n-ethylpentylone can be as little as 30 milligrams. If people believe they have MDMA and take 100 milligrams of n-ethylpentylone, then they are going to be in a very risky situation.

Excerpt from Know Your Stuff NZ:
https://knowyourstuff.nz/2018/02/07/this-summers-crap-drug-n-ethylpentylone/

World Health Organization 2018:
It originally emerged in the 1960s during pharmaceutical drug development efforts. Another common name used widely is N-ethylpentylone. On the streets,N-ethylnorpentylone is most likely available as the racemic mixture and it might be obtained from Internet retailers.In the United States of America (USA), this substance was detected for the first time in 2014 but began to emerge more prominently in 2016 both in the USA and other UN Member States. Seizures indicate that N-ethylnorpentylone is available in powder, crystal, rock, capsule, and tablet forms. Examples exist where this drug has been surreptitiously sold as 'ecstasy'/MDMA.

World Health Organization N-Ethylpentylone (PDF 30 pages):
https://www.who.int/medicines/access/controlled-substances/N-Ethylnorpentylone.pdf

Erowid Experience Vault:
https://erowid.org/experiences/subs/exp_NEthylpentedrone.shtml

Bluelight Forum:
https://www.bluelight.org/xf/threads/novel-stimulant-ephylone-n-ethyl-pentylone-%CE%B2k-ethyl-k-%CE%B2k-ebdp.774023/

A Reddit Discussion:
https://www.reddit.com/r/researchchemicals/comments/5alj8i/ephylone_one_not_so_small_report_for_you_one/

DEA N-Ethylpentylone (PDF 1 page):
https://www.deadiversion.usdoj.gov/drug_chem_info/n-ethylpentylone.pdf

N-Ethylpentylone:

N-ethylpentylone "can cause circulation problems, lethal heart palpitations and hallucinations". It has been linked to a number of overdose deaths and mass-casualty incidents, and has increasingly been missold as MDMA.

• A substituted cathinone and stimulant drug
• Developed in the 1960s

It has been reported as a novel designer drug in several countries including South Africa, New Zealand, the United States, and Australia. In 2018, N-ethylpentylone was the most common drug of the cathinone class to be identified in Drug Enforcement Administration seizures