Promethazine is a neuroleptic medication and first-generation antihistamine of the phenothiazine family. The drug has strong and weak antipsychotic effects. It also reduces motion sickness and has antiemetic (Histamine H1 receptors but it does not block the production of histamine) and anticholinergic properties. In some countries it is prescribed for insomnia when are contraindicated. It is available in many countries under many brand names.^[1][4] Promethazine was developed in the mid 1940s when a team of scientists from Rhône-Poulenc laboratories were able to synthesize it from phenothiazine and a diamine side chain of diphenhydramine

Some documented side effects include:

• Tardive dyskinesia (effects due to dopamine D2 receptor antagonism)
• Confusion in the elderly
• Drowsiness, dizziness, fatigue, more rarely vertigo
• Dry mouth
• Respiratory depression in patients under age of two and in those with severely compromised pulmonary function
• Constipation
• Chest discomfort/pressure (typically in cases when patient is already taking medication for high blood pressure)
• Akathisia ^[10]
• Paresthesia
• Short temper/irritability