**1. Introduction**

Dysphagia relates to swallowing problems due to physiological changes in aging people or such factors as diseases and medications [1]. Previous studies stated that world prevalence of dysphagia ranged between 16% and 22% [2]. Dysphagia can be classified into two types: oropharyngeal and esophageal. Oropharyngeal dysphagia includes cerebrovascular disorders (like stroke), central nervous system disorders (like Parkinson's disease), and others (like thyroid disorders). Esophageal dysphagia includes aging, alcoholism, diabetes mellitus (DM), cancers, and medications [3]. Several symptoms detected to determine the type of dysphagia (i.e. swallowing problems) included gastrointestinal symptoms (such as heartburn, indiges‐ tion, and gastro-esophageal reflux disease), respiratory symptoms (like cough), and muscu‐ loskeletal chest pain [4].

Many medications are known to induce dysphagia by affecting smooth and striated muscle via increasing the sensitivity of mucosa resulting in swallowing difficulty. There are two different ways in which this occurs. First, there is the normal adverse effect (or the indirect effect) due to pharmacological action and complications such as dysphagia induced by antibiotics as well as immunosuppressive and anti-cancer agents. Second, there is the direct effect of medications irritating the mucosa, which is more observed in the elderly [5]. The aortic arch is the area most susceptible to injuries induced by pills. Medications with a pH less than 3 (such as doxycycline and tetracycline) as well as certain slow-release anticholinergic dosage medications were more caustic resulting in moderate and severe injuries [6]. The severity of injuries depended on chronic irritation, high osmolarity, and the dissolution rate of dosage forms [7]. Medications that are known to induce dysphagia can be categorized into four groups [8]: (1) medications affecting smooth muscle such as theophylline and calcium channel

© 2015 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

blockers; (2) medications reducing esophageal sphincter pressure such as nitrates and atropine; (3) medications inducing xerostomia such as antihypertensive agents and antiarrhythmics; and (4) medications inducing esophageal injury such as aspirin and non-steroidal antiinflammatory medications.

Polypharmacy is defined as patient use of five or more medications [9]. Polypharmacy contributes to the high incidence of adverse effects as a consequence of possible drug interactions between medications [10, 11]. Although some studies state that polypharma‐ cy should be considered a significant predictor for dysphagia [2, 12], they have weakness‐ es in that they were either case reports or mainly dealt with specific dysphagia type. Thus, the aims of the current study are, first, to describe the incidence, severity, and predictors of dysphagia; second, to determine the relationship between polypharmacy and dyspha‐ gia; and, third, to describe the association between types of dysphagia (depending on concurrent symptoms) and polypharmacy.
