A combination of alcohol and antihistamine may leads to

Options

A. Marked drowsiness
B. High risk of damage to gastric mucosa
C. Hypertension
D. Decreased insulin effect

Answer

### Step-by-Step Solution:

1. **Understanding the Components**:
- The question involves two substances: alcohol and antihistamines. Antihistamines are medications that reduce allergy symptoms.

2. **Effects of Alcohol**:
- Alcohol is a central nervous system (CNS) depressant, which means it slows down brain function and neural activity.

3. **Effects of Antihistamines**:
- Antihistamines, especially first-generation ones like diphenhydramine (Benadryl), also have sedative effects and can act as CNS depressants.

4. **Combining Alcohol and Antihistamines**:
- When alcohol is combined with antihistamines, both substances can enhance each other's sedative effects. This can lead to increased drowsiness and impaired cognitive and motor functions.

5. **Potential Risks**:
- The combination can lead to marked drowsiness, which can affect the ability to perform tasks that require alertness, such as driving.
- Additionally, there is a risk of damage to the gastric mucosa due to the irritative effects of alcohol, and it may also lead to other health issues like hypertension and decreased insulin effect.

6. **Conclusion**:
- Given the options provided in the question, the most significant and immediate effect of combining alcohol and antihistamines is marked drowsiness.

### Final Answer:
- A combination of alcohol and antihistamine may lead to **marked drowsiness**.