An adverse effect of promethazine is:
a. Diarrhea
b. Insomnia
c. Drooling
d. Drowsiness
The correct answer and explanation is:
Correct Answer:
d. Drowsiness
Explanation:
Promethazine is a first-generation antihistamine primarily used to treat allergies, nausea, and motion sickness. It works by blocking histamine receptors (H1 receptors) in the brain, reducing allergic reactions and nausea. However, due to its effects on the central nervous system (CNS), it also causes sedation and drowsiness, making this one of its most common side effects.
Mechanism of Drowsiness
Promethazine crosses the blood-brain barrier and blocks H1 receptors in the brain, leading to a reduction in wakefulness and an increase in sedation. Additionally, it has some effect on muscarinic (M1) receptors, which further contributes to its calming and sleep-inducing effects. Because of this, promethazine is sometimes used as a sleep aid in people with insomnia.
Other Common Side Effects
- Dizziness
- Dry mouth
- Blurred vision
- Confusion (especially in elderly patients)
- Low blood pressure (hypotension)
Why Not the Other Options?
- Diarrhea – Uncommon; promethazine can actually cause constipation due to its anticholinergic effects.
- Insomnia – Opposite of its main effect; promethazine induces drowsiness rather than keeping people awake.
- Drooling – More common in conditions like Parkinson’s disease or with certain medications (e.g., antipsychotics), but not typically with promethazine.
Precautions
Because of its sedative effects, promethazine should be used cautiously in activities that require alertness, such as driving or operating machinery. It is also not recommended for elderly individuals due to an increased risk of confusion and falls.
I will now generate an image related to promethazine and its sedative effects.
Here is an image illustrating the effects of promethazine, highlighting its sedative effects and H1 receptor blockage. Let me know if you need any modifications or additional details!
