Selecting the optimal oral antihistamine for patients with allergic rhinitis.

Allergic rhinitis (AR) is now recognised as a global health problem that affects 10-30% of adults and up to 40% of children. Each year, millions of patients seek treatment from their healthcare provider. However, the prevalence of AR maybe significantly underestimated because of misdiagnosis, under diagnosis and failure of patients to seek medical attention. In addition to the classical symptoms such as sneezing, nasal pruritus, congestion and rhinorrhoea, it is now recognised that AR has a significant impact on quality of life (QOL). This condition can lead to sleep disturbance as a result of nasal congestion, which leads to significant impairment in daily activities such as work and school. Traditionally, AR has been subdivided into seasonal AR (SAR) or perennial AR (PAR). SAR symptoms usually appear during a specific season in which aeroallergens are present in the outdoor air such as tree and grass pollen in the spring and summer and weed pollens in the autumn (fall); and PAR symptoms are present year-round and are triggered by dust mite, animal dander, indoor molds and cockroaches. Oral histamine H(1)-receptor antagonists (H(1) antihistamines) are one of the most commonly prescribed medications for the treatment of AR. There are several oral H(1) antihistamines available and it is important to know the pharmacology, such as administration interval, onset of action, metabolism and conditions that require administration adjustments. When prescribing oral H(1) antihistamines, the healthcare provider must take into account the clinical efficacy and weigh this against the risk of adverse effects from the agent. In addition to the clinical efficacy, potential for improvement in QOL with a particular treatment should also be considered.