4-HO-MPT, or 4-hydroxy-N-methyl-N-propyltryptamine, is a lesser-known psychedelic drug. It is the 4-hydroxyl analog of MPT. 4-HO-MPT was first synthesized by Alexander Shulgin. In his book TiHKAL (Tryptamines I Have Known and Loved), the minimum dosage is listed as 10-20 mg, and the duration listed as 4-6 hours. 4-HO-MPT produces visual distortion, vertigo, and slight insomnia. Very little data exists about the pharmacological properties, metabolism, and toxicity of 4-HO-MPT.