From the Guidelines
Antihistamines should be prescribed with caution in patients with type 2 diabetes and heart disease, as they may pose significant risks, including worsening blood glucose control and increasing the risk of arrhythmias. When considering antihistamine use in these patients, it is crucial to weigh the potential benefits against the risks. First-generation antihistamines, such as diphenhydramine, can cause drowsiness, urinary retention, and dry mouth, while potentially worsening blood glucose control in diabetic patients 1. Additionally, they may cause QT interval prolongation, increasing the risk of arrhythmias in patients with heart disease.
Key Considerations
- Second-generation antihistamines, like cetirizine and loratadine, are generally safer but still require caution due to potential interactions with other medications and effects on blood glucose levels.
- Fexofenadine is often preferred for patients with type 2 diabetes and heart disease because it has minimal cardiac effects and does not significantly affect blood glucose levels.
- Patients should start with the lowest effective dose and monitor their blood glucose levels regularly, watching for signs of cardiac issues like palpitations or dizziness.
- A complete medication review is essential to identify potential interactions between antihistamines and common medications for diabetes and heart disease.
Recommendations
- Non-sedating antihistamines taken in the morning can help minimize drowsiness.
- Patients should avoid alcohol, as it can worsen side effects.
- The use of antihistamines in patients with type 2 diabetes and heart disease should be guided by the most recent and highest-quality evidence, such as the standards of care in diabetes-2023, which emphasizes the importance of cardiovascular risk management in patients with diabetes 1.
From the Research
Risks Involved with Antihistamine Prescription
The patient in question has type two diabetes and heart disease, and the prescription of an antihistamine may pose certain risks.
- The primary concern is the potential for cardiac toxicity, particularly QT prolongation and torsades de pointes (TdP) 2, 3.
- However, studies have shown that certain second-generation antihistamines, such as loratadine, cetirizine, and fexofenadine, are not associated with QT prolongation or TdP 4, 2, 3, 5.
- These antihistamines have been shown to have excellent safety records, including in patients with cardiovascular disease 4, 6.
- Nevertheless, it is essential to consider potential risk factors for cardiotoxicity, such as inherited long QT syndrome, older age, cardiovascular disorders, hypokalemia, and hypomagnesemia, or the use of drugs that can prolong the QT interval 2, 6.
Specific Antihistamines and Their Safety Profiles
- Loratadine has been shown to be safe and not associated with performance impairment or cardiotoxicity 4, 5.
- Cetirizine has been found to be safe, with no evidence of cardiotoxicity, although it may impair performance and cognition to a lesser degree than older antihistamines 4, 5.
- Fexofenadine is also considered safe, with no evidence of QT prolongation or TdP 2, 3, 5.
- It is crucial to note that the safety profile of these antihistamines may be affected by updosing, and prescribers should carefully consider potential risk factors for cardiotoxicity 6.