ó-Hydroxyvaleric acid (GHV), also known as 4-methyl-GHB, is a designer drug related to ó-hydroxybutyric acid (GHB). It is sometimes seen on the grey market as a legal alternative to GHB, but with lower potency and higher toxicity, properties which have tended to limit its recreational use.
ó-Valerolactone (GVL) acts as a prodrug to GHV, analogously to how ó-butyrolactone (GBL) is a prodrug to GHB.