Side Effects of Promethazine

Promethazine belongs to a group of drugs called phenothiazines. It acts as an antihistamine and obstructs the effects of the naturally occurring chemical histamine in the body. It functions by mutating the actions of chemicals in the brain. It is a first-generation H₁ receptor antagonist and antiemetic medication. It prevents nausea and vomiting caused by illness or any kind of motion sickness. Promethazine is usually given to the patient before surgery as it helps the patient to sleep and treats the pain or nausea even after the surgery. It is used to treat allergy symptoms like sneezing, itching, runny nose, hives, itchy or watery eyes and itchy skin rashes. It has anti-cholinergic, anti-emetic and anti-motion sickness effects. Some of its other medical benefits are:

• It counteracts postnarcotic nausea and is used for preoperative sedation.
• It fights hay fever, allergic rhinitis, etc and can be used alone or in combination with oral decongestants like pseudoephedrine to cure different allergic reactions.
• It is used as an adjunct treatment for anaphylactoid conditions.
• It cures moderate to severe hyperemesis gravidarum, motion sickness or sea sickness when used alone or in combination with Ephedrine.

Side Effects of Promethazine
Common side effects of promethazine include:

• Drowsiness, dizziness, fatigue
• Seizures
• Constipation
• Dry mouth
• Neuroleptic malignant syndrome
• Euphoria, restless legs, paresthesia

The prolonged consumption of promethazine can lead to skin hyperpigmentation or darkening which is restricted to the areas of the body exposed to sunlight. Hence, people undergoing treatment should use sunscreens and avoid direct exposure to the sun. It cannot be used for treating symptoms of asthma, pneumonia, or any other lower respiratory tract infections. It also causes blurred vision, changes in color vision, dilated pupils and difficulty with nighttime vision. Liver damage is rare, but newborns may suffer from jaundice, if the mother is given promethazine during pregnancy. It blocks the dopamine receptors which leads to increased levels of the prolactin hormone, which is involved in the formation of breast milk. As a result, it causes the breast to produce milk even when a woman is not pregnant. In addition to this, it leads to weight gain, missed menstrual periods, breast enlargement, loss of sexual drive, impotence and priapism. Promethazine should not be used in children under the age of two as it causes respiratory depression and then leads to death. It should not be used with propylthiouracil, an antithyroid agent, as it reduces the white blood cell count and increases the risks of infections. Promethazine should not be consumed with any of the mono-amine oxidase (MAO) inhibitor-class of antidepressants as it increases the risk of extrapyramidal symptoms (EPS), an uncontrollable movement disorder. It also causes restlessness, inability to sleep, nausea, urinary retentions and heart palpitations.

These complications can become severe if ignored and not provided with proper parenteral administration, hence resulting in surgical interventions and operations. It is always recommended to give promethazine in a diluted form with a concentration not greater than 25mg per ml, through an existing intravenous set in a large vein.