The H1-antihistamines have been reclassified as inverse agonists, rather than as H1-receptor antagonists (Simons 2004). The first generation H1-antihistamines are well-known antiallergy medications. They may occasionally cause an increase in the pulse rate because they have an atropine-like effect. In some individuals, the heart rate may become rapid. These sensations, called palpitations and caused by arrhythmia, subside over time and usually cause no harm ( Arrhythmias). Patients with angina, however, should be cautious with the use of antihistamines, because an increase in heart rate may trigger an attack of angina ( Angina). Blood pressure is usually not increased by antihistamine use, but many remedies containing antihistamines contain the decongestant phenyl propanolamine, which elevates blood pressure ( Blood Pressure). This should be avoided in patients with hypertension and angina ( Hypertension).
These agents do not produce the bothersome side...