Motilin

Where it comes from

Made in

M cells of the duodenum and upper jejunum

Sent out by

In pulses during fasting, every 90 to 120 minutes, in step with the migrating motor complex; eating stops it

Acts on

• Stomach and duodenal smooth muscle
• Enteric nerves
• Gallbladder

What it does

• Starts the “housekeeper” contractions that sweep the empty stomach and small intestine ¹
• Its contractions are the stomach’s growl
• Rats, mice and guinea pigs lack a working motilin system, which held research back for decades; rabbits and dogs are the models ²

In medicine

• Erythromycin and azithromycin act on the motilin receptor, which is why they are used off-label to empty a sluggish stomach ¹
• Motilin agonists built as drugs (camicinal, mitemcinal) did not get through trials for gastroparesis

Beyond the body’s own use

• Motilin itself is not given as a medicine: it lasts minutes in blood and there is no form that survives the gut
• The purpose-built agonists came closer than their fate suggests. Camicinal sped the absorption of levodopa and cut off-time by more than two hours a day in a randomised trial in Parkinson’s disease ³, but neither it nor mitemcinal was carried to approval
• Its pulses line up with the pangs of hunger during a fast, which is studied. Because the usual laboratory rodents have no working motilin system, almost everything known rests on people, dogs and rabbits ²