Methyprylon (brand name Noludar) is a sedative agent, which used to treat insomnia. But then the drug was replaced in the market by another drugs with less side effects. The precise mechanism of action is not known, but was made suggestion, that methyprylon increases the effects of gamma-aminobutyric acid (GABA), an inhibitory neurotransmitter in the brain.

Methyprylon:
https://drugs.ncats.io/drug/CUT48I42ON

Piperidinediones:
Methyprylon, also known as noludar or metiprilon, belongs to the class of organic compounds known as piperidinediones. Piperidinediones are compounds containing a piperidine ring which bears two ketones. Methyprylon is a drug. Methyprylon is an extremely weak basic (essentially neutral) compound (based on its pKa). Methyprylon is a potentially toxic compound. Methyprylon (Noludar) was a sedative of the piperidinedione derivative family developed by Hoffmann-La Roche. A study of single oral doses of 300 mg in healthy volunteers found that the zero-order absorption model fit the data best. A case report found that the pharmacokinetics of methyprylon were not concentration dependent in an overdose case; explanations included saturation or inhibition of metabolic pathways. Side effects can include skin rash, fever, depression, ulcers or sores in mouth or throat, unusual bleeding or bruising, confusion, fast heartbeat, respiratory depression, swelling of feet or lower legs, dizziness, drowsiness, headache, double vision, clumsiness, constipation, diarrhea, nausea, vomiting, unusual weakness. Some other trade names are Noctan and Dimerin. Methyprylon was withdrawn from the US market in June 1965 and the Canadian market in September 1990. The generally accepted half-life for a therapeutic dose was not found appropriate in intoxicated patients and would underestimate the time required to reach a safe concentration of the drug.

Metabocard for Methyprylon:
https://hmdb.ca/metabolites/HMDB0015239

Pharmacology:
Methyprylon, a piperidinedione CNS depressant, is close to barbituric acid in structure, but different enough to be called a "non-barbiturate" sedative-hynotic. Methyprylon is used for insomnia and daytime tension. Methyprylon depresses the activity of muscle tissues, the heart, and the respiratory system.

Methyprylon - Brands, Medical Use, Clinical Data: http://www.druglib.com/activeingredient/methyprylon/

Half-life:
Plasma half-life is 6 to 16 hours

Onset of action:
Within 45 minutes

Duration of action:
5 to 8 hours

Methyprylon has been shown to be effective for at least 7 consecutive nights. If this medication is used for the treatment of insomnia, prolonged use of methyprylon is generally not recommended.

Methyprylon (Systemic):
https://www.drugs.com/mmx/methyprylon.html

Methyprylon Reddit Search Results:
https://www.reddit.com/search/?q=Methyprylon

Routes of administration: oral