Sildenafil Affects Olfactory Function

Olfactory Function and Olfactory Disorders

The sense of smell is important. This became especially clear to patients with infection-related olfactory loss during the SARS-CoV-2 pandemic. We react, for example, to the body odors of other humans. The sense of smell warns us of danger, and it allows us to perceive flavors when eating and drinking. In essence, this means quality of life. Therefore, anosmia must be taken seriously. Although olfactory receptor neurons are characterized by regenerative capacity, anosmia is relatively common with about 5 % of anosmic people in the general population. Olfactory disorders are classified according to their causes (e. g., infections of the upper respiratory tract, traumatic brain injury, chronic rhinosinusitis, age) with the resulting different therapeutic options and prognoses. Thorough history taking is therefore important. A wide variety of tools are available for diagnosis, ranging from short screening tests and detailed multidimensional test procedures to electrophysiological and imaging methods. Thus, quantitative olfactory disorders are easily assessable and traceable. For qualitative olfactory disorders such as parosmia, however, no objectifying diagnostic procedures are currently available. Therapeutic options for olfactory disorders are limited. Nevertheless, there are effective options consisting of olfactory training as well as various additive drug therapies. The consultation and the competent discussion with the patients are of major importance.

International consensus statement on allergy and rhinology: Olfaction

BACKGROUND

The literature regarding clinical olfaction, olfactory loss, and olfactory dysfunction has expanded rapidly over the past two decades, with an exponential rise in the past year. There is substantial variability in the quality of this literature and a need to consolidate and critically review the evidence. It is with that aim that we have gathered experts from around the world to produce this International Consensus on Allergy and Rhinology: Olfaction (ICAR:O).

METHODS

Using previously described methodology, specific topics were developed relating to olfaction. Each topic was assigned a literature review, evidence-based review, or evidence-based review with recommendations format as dictated by available evidence and scope within the ICAR:O document. Following iterative reviews of each topic, the ICAR:O document was integrated and reviewed by all authors for final consensus.

RESULTS

The ICAR:O document reviews nearly 100 separate topics within the realm of olfaction, including diagnosis, epidemiology, disease burden, diagnosis, testing, etiology, treatment, and associated pathologies.

CONCLUSION

This critical review of the existing clinical olfaction literature provides much needed insight and clarity into the evaluation, diagnosis, and treatment of patients with olfactory dysfunction, while also clearly delineating gaps in our knowledge and evidence base that we should investigate further.

Short-Course Pentoxifylline Is Not Effective in Post-Traumatic Smell Loss: A Pilot Study

It has been suggested that systemic pentoxifylline may be beneficial in the treatment of olfactory dysfunction. The postulated mechanism of action involves nonselective competitive phosphodiesterase inhibition, leading to increased intracellular cyclic adenosine monophosphate and consequent increased olfactory neuron activity. This should in theory lead to improved olfactory function. We describe a pilot case series from our tertiary referral center of patients treated with oral pentoxifylline for olfactory dysfunction. Six patients with post-traumatic impairment who were treated with systemic pentoxifylline were included. Patients were treated with 200 mg of oral prolonged release pentoxifylline, 3 times a day for 21 days. Olfactory function was tested pre and post-treatment for odor threshold (T), discrimination (D), identification (I) and composite 'TDI' score using a psychophysical test battery, the "Sniffin' Sticks." Oral pentoxifylline was well tolerated and all patients completed the treatment period. There was a small improvement in odor threshold and identification scores, but these did not reach statistical or clinical significance. There were deteriorations in discrimination and composite TDI score, which did not reach significance. While our case series was small, systemic pentoxifylline did not appear to be beneficial in the treatment of hyposmia in this patient group.

Toxic exposures and the senses of taste and smell

This review addresses the adverse influences of neurotoxic exposures on the ability to smell and taste. These chemical senses largely determine the flavor of foods and beverages, impact food intake, and ultimately nutrition, and provide a warning for spoiled or poisonous food, leaking natural gas, smoke, airborne pollutants, and other hazards. Hence, toxicants that damage these senses have a significant impact on everyday function. As noted in detail, a large number of toxicants encountered in urban and industrial air pollution, including smoke, solvents, metals, and particulate matter can alter the ability to smell. Their influence on taste, i.e., sweet, sour, bitter, salty, and savory (umami) sensations, is not well documented. Given the rather direct exposure of olfactory receptors to the outside environment, olfaction is particularly vulnerable to damage from toxicants. Some toxicants, such as nanoparticles, have the potential to damage not only the olfactory receptor cells, but also the central nervous system structures by their entrance into the brain through the olfactory mucosa.

Machine-learned pattern identification in olfactory subtest results

The human sense of smell is often analyzed as being composed of three main components comprising olfactory threshold, odor discrimination and the ability to identify odors. A relevant distinction of the three components and their differential changes in distinct disorders remains a research focus. The present data-driven analysis aimed at establishing a cluster structure in the pattern of olfactory subtest results. Therefore, unsupervised machine-learning was applied onto olfactory subtest results acquired in 10,714 subjects with nine different olfactory pathologies. Using the U-matrix, Emergent Self-organizing feature maps (ESOM) identified three different clusters characterized by (i) low threshold and good discrimination and identification, (ii) very high threshold associated with absent to poor discrimination and identification ability, or (iii) medium threshold, i.e., in the mid-range of possible thresholds, associated with reduced discrimination and identification ability. Specific etiologies of olfactory (dys)function were unequally represented in the clusters (p < 2.2 · 10-16). Patients with congenital anosmia were overrepresented in the second cluster while subjects with postinfectious olfactory dysfunction belonged frequently to the third cluster. However, the clusters provided no clear separation between etiologies. Hence, the present verification of a distinct cluster structure encourages continued scientific efforts at olfactory test pattern recognition.

Pharmacogenetics of erectile dysfunction: navigating into uncharted waters

Sildenafil and other PDE-5 inhibitors have revolutionized erectile dysfunction (ED) treatment. However, a significant number of patients do not respond or present adverse reactions to these drugs. While genetic polymorphisms may underlie this phenomenon, very little research has been undertaken in this research field. Most of the current knowledge is based on sildenafil, thus almost completely ignoring other important pharmacological therapies. Currently, the most promising genes with pharmacogenetic implications in ED are related to the nitric oxide and cGMP pathway, although other genes are likely to affect the responsiveness to treatment of ED. Nevertheless, the small number of studies available opens the possibility of further exploring other genes and phenotypes related to ED. This article provides a comprehensive overview of the genes being tested for their pharmacogenetic relevance in the therapy of ED.

Olfactory drug effects approached from human-derived data

The complexity of the sense of smell makes adverse olfactory effects of drugs highly likely, which can impact a patient's quality of life. Here, we present a bioinformatics approach that identifies drugs with potential olfactory effects by connecting drug target expression patterns in human olfactory tissue with drug-related information and the underlying molecular drug targets taken from publically available databases. We identified 71 drugs with listed olfactory effects and 147 different targets. Taking the target-based approach further, we found additional drugs with potential olfactory effects, including 152 different substances interacting with genes expressed in the human olfactory bulb. Our proposed bioinformatics approach provides plausible hypotheses about mechanistic drug effects for drug discovery and repurposing and, thus, would be appropriate for use during drug development.

Histopathologic results of long-term sildenafil administration on rat inner ear

OBJECTIVES

Sildenafil, a selective inhibitor of phosphodiesterase type 5, is widely used for the treatment of erectile dysfunction. Although cochlear effects of phosphodiesterase type 5 inhibitors remain still unclear because of inadequate data, some evidence that recently emerged indicates that these medications may be responsible for hearing impairment. In the present study, we aimed to examine the histopathologic effects of long-term sildenafil use on the cochlea in a rat model.

METHODS

The study was performed with adult male Wistar albino rats. The control group was fed on standard laboratory diet. The study group was applied orally with sildenafil therapy, 1.5 mg/kg once a day for 45 days. Rats were anesthetized and decapitated. Each temporal bone was dissected, and the cochleas were removed en bloc. The inner-ear biopsy specimens were examined histologically with hematoxylin and eosin and caspase 3 immunoreaction under light microscopy.

RESULTS

Hematoxylin and eosin staining showed no distinctive difference between the control group and the sildenafil group. With immunohistochemical examination, caspase 3 immunoreactivity was observed in the sildenafil group. In the control group, caspase 3 immunoreactivity was not observed.

CONCLUSIONS

The caspase 3 immunoreactivity in the sildenafil group was strongly associated with an increase in apoptotic events in the cochlea. Long-term use of sildenafil can cause hearing impairment through increased apoptosis.

Sniffing out pharmacology: interactions of drugs with human olfaction

Advances in the understanding of the sense of smell have increased awareness of the role of olfaction in human life. Odors are perceived via specific G protein-coupled receptors (GPCRs) with cAMP as the second messenger. Drugs that interact with this signaling cascade, such as opioids, cannabinoids and sildenafil, are known to reduce olfactory function. Drugs that are active in the central nervous system (CNS) may also hinder the complex processing of olfactory information to distinguish, via pattern recognition, thousands of odors from the signals of only ∼400 distinct olfactory receptors. Many other interactions with drug targets expressed at the olfactory bulb are also likely to occur. However, olfactory drug effects have rarely been explored in controlled studies. In the current activities of drug development and re-purposing, olfaction could become highly important because it can impact significantly upon the enjoyment of food. With an established molecular basis and using available tools, the assessment of olfaction in drug development and approval is advised.

Drugs and nutrition: how side effects can influence nutritional intake

There are many factors that can influence nutritional intake. Food availability, physical capability, appetite, presence of gastrointestinal symptoms and perception of food are examples. Drug therapy can negatively influence nutritional intake through their effect on these factors, predominantly due to side effects. This review aims to give a brief overview of each of these factors and how drug therapy can affect them. Specific examples are given for each section and an indication of the impact on nutritional status. This article aims to assist the clinician in the identification of the effects of drug therapy on nutritional intake and provides advice on appropriate intervention. A drug history and side effect review should form an integral part of nutritional assessment. Early identification and effective therapeutic use of alternative drug therapy can also positively influence nutritional intake.

Pharmacogenetics and pharmacogenomics of sexual dysfunction: current status, gaps and potential applications

Although treatment of different types of sexual dysfunction has improved in the past decade with the introduction of phosphodiesterase type 5 inhibitors and selective serotonin reuptake inhibitors, response rates to these targeted therapies are variable. There are a number of studies in the published literature that provide proof-of-concept that genetic variation contributes to the variable response. Pharmacogenomics will most likely be one part of our therapeutic armamentarium in the future and will provide a stronger scientific basis for optimizing drug therapy on the basis of each patient’s genetic constitution. This article will review English language medical literature on the state-of-the-art genetic polymorphisms of drug targets, transporters and signaling molecules as well as pharmacogenetic studies of sexual dysfunction and suggested possible applications. Collectively, the data demonstrate that pharmacogenomics in the field of sexual medicine is still in its infancy. More research will provide further intriguing new discoveries in years to come.

Effect of phosphodiesterase-5 inhibitor on hearing

Objective:

Following a report of sudden hearing loss in a patient taking phosphodiesterase type 5 inhibitor, and a Food and Drug Administration announcement concerning this class of drugs, a study was planned to investigate if ototoxicity occurs in patients using phosphodiesterase 5 inhibitor for erectile dysfunction.

Methods:

Eighteen patients with erectile dysfunction who had been using phosphodiesterase 5 inhibitor were included in the study. Audiometric tests were performed on all patients, between the frequencies 250 and 16 000 Hz, before and 1, 5 and 72 hours after drug ingestion.

Results:

Four patients showed a unilateral threshold decrease compatible with ototoxicity criteria; this change was reversible. A statistically significant difference in pre- versus post-drug hearing thresholds was observed in the right ear at 10 000 Hz (p = 0.008). There were no statistically significant hearing threshold differences at any other frequencies (p > 0.05).

Conclusion:

Although temporary ototoxicity was noted in four patients, we could not find any permanent, deleterious effect of phosphodiesterase type 5 inhibitor on hearing thresholds.