Promethazine®

What is Promethazine?

Promethazine is a type of antihistamine that’s prescribed off-label to manage morning sickness. Changes in your hormone levels during pregnancy can make you feel nauseous or cause you to vomit, often called morning sickness. Promethazine blocks histamine receptors in your brain, which play a role in your nausea and vomiting responses. This should help reduce symptoms of nausea, and prevent morning sickness.

Who can use Promethazine?

Promethazine is suitable for most adults to use. Speak to your doctor if you have: difficulty breathing, epilepsy, heart problems, liver problems, kidney problems, a stomach blockage, difficulty urinating, hearing problems, glaucoma, or Reye’s syndrome before using Promethazine.

How do Promethazine doses work?

Promethazine comes in 12.5, 25, and 50 mg doses. You’ll be prescribed the lowest dose that keeps your morning sickness in check, to keep the risk of any side effects to a minimum. If you feel that your current dose isn’t enough to manage your symptoms, or you’re getting side effects on your current dose, speak to your healthcare provider about changing your dosage.

What is Promethazine’s active ingredient?

Promethazine is a generic drug named after its active ingredient, promethazine. It’s a type of medicine we call phenothiazines, and works by blocking the natural chemical histamine. This is why Promethazine is also referred to as an antihistamine.

How does Promethazine work?

Histamine is a natural chemical that’s released by specialized cells in our body called mast cells. This is usually in response to allergens, but can be released because of other reasons, too. Histamine ‘activates’ receptors in your brain that are involved with nausea and vomiting, specifically the H1 receptor, which can cause you to be sick.^[1]

Promethazine is a type of antihistamine that blocks the H1 receptor in your brain. This stops histamine from binding to H1 receptors, which should help reduce feelings of nausea and vomiting during pregnancy.^[2]

How to take Promethazine for morning sickness

You’ll usually take your prescribed dose of Promethazine each night to manage morning sickness the next day. But if that isn’t enough to manage your nausea, you can take promethazine every 4-6 hours, as needed.^[1] But you shouldn’t take more than 100 mg of Promethazine each day.^[2]