In vivo studies on the effects of α1-adrenoceptor antagonists on pupil diameter and urethral tone in rabbits

Potential side effects of currently available pharmacotherapies in male lower urinary tract symptoms suggestive of benign prostatic hyperplasia

INTRODUCTION

The drug classes of α1-adrenoceptor antagonists, 5α-reductase inhibitors, and phosphodiesterase type 5 inhibitors are guideline-recommended treatments of lower urinary tract symptoms suggestive of benign prostatic hyperplasia; muscarinic receptor antagonists and β3-adrenoceptor agonists are also recommended if storage symptoms are insufficiently addressed with one of the other three drug classes.

AREAS COVERED

We provide a narrative review (no formalized literature searches performed) of the tolerability of these drug classes with emphasis on the more recently introduced medications, on combination treatment, and on more lately emerging risks.

EXPERT OPINION/COMMENTARY

The tolerability profiles are distinct between drug classes but, with few exceptions, similar within a drug class. Within a drug, formulations with longer duration of action tend to have better tolerability. Efficacy gains using combination treatment at least partly come at a cost of lesser tolerability. Greater susceptibility to experience adverse events based on age, comorbidities, and comedications appears conceptually important but remains under-investigated in this therapeutic area.

Preclinical applications of high-definition manometry system to investigate pelvic floor muscle contribution to continence mechanisms in a rabbit model

External anal sphincter (EAS), external urethral sphincters, and puborectalis muscle (PRM) have important roles in the genesis of anal and urethral closure pressures. In the present study, we defined the contribution of these muscles alone and in combination with the sphincter closure function using a rabbit model and a high-definition manometry (HDM) system. A total of 12 female rabbits were anesthetized and prepared to measure anal, urethral, and vaginal canal pressures using a HDM system. Pressure was recorded at rest and during electrical stimulation of the EAS and PRM. A few rabbits (n = 6) were subjected to EAS injury and the impact of EAS injury on the closure pressure profile was also evaluated. Anal, urethral, and vaginal canal pressures recorded at rest and during electrical stimulation of EAS and PRM demonstrated distinct pressure profiles. EAS stimulation induced anal canal pressure increase, whereas PRM stimulation increased the pressures in all the three orifices. Electrical stimulation of EAS after injury resulted in about 19% decrease in anal canal pressure. Simultaneous electrical stimulation of EAS and PRM resulted in an insignificant increase of individual anal canal pressures when compared with pressures recorded after EAS or PRM stimulations alone. Our data confirm that HDM is a viable system to measure dynamic pressure changes within the three orifices and to define the role of each muscle in the development of closure pressures within these orifices in preclinical studies.NEW & NOTEWORTHY We anticipate that with this new HDM technology, physiological changes within these orifices may be redefined using the extensive data that are generated from 96 sensors. When compared with conventional methods, HDM offers the advantages of an increased response rate, as well as the utilization of 96 circumferential sensors to simultaneously measure pressure along the three orifices. Our findings suggest a potential use of this technology to better define urinary leak point pressure.

Evaluation of static and dynamic Pupillometry changes in men using Silodosin for benign prostatic hypertrophy

Background

Intraoperative floppy iris syndrome is a variant of the small pupil syndrome that has been observed during cataract surgery in some patients currently or previously treated with α1 adrenergic blockers. It is important for cataract surgeons to predict the probable complications preoperatively. Our study aims to evaluate the static and dynamic pupil characteristics of patients treated with silodosin—a selective α1 adrenergic blocker—for benign prostate hypertrophy (BPH) and to compare these values with healthy subjects using an automatic quantitative pupillometry system.

Methods

A total of 74 BPH patients treated with silodosin for six months (group 1) and 30 healthy subjects (group 2) were enrolled in this prospective multidisciplinary cross-sectional study. Static and dynamic pupillometric measurements were obtained under optimized conditions, and the results were compared between the two groups.

Results

Seventy-four male patients with a mean age of 63,35 ± 7,21 (46–77) years with BPH treated with silodosin and 30 normal male subjects with a mean age of 63,07 ± 4,73 (52–71) years were analyzed. There were statistically significant differences between the groups with regard to scotopic pupil diameter (PD), high photopic PD, and low photopic PD (p < 0.001, for each one). The patient group had statistically significant higher values of amplitude and velocity of pupil contraction and lower values of duration of pupil contraction and latency as well as duration and velocity of pupil dilation.

Conclusion

The static and dynamic pupil characteristics of subjects treated with silodosin for BPH are different from those of healthy eyes. In addition, our results may have shed light on the risk for intraoperative floppy iris syndrome (IFIS) before cataract surgery; thus, surgeons can be alert and take precautions.

Isoform-specific dynamic translocation of PKC by α1-adrenoceptor stimulation in live cells

Protein kinase C (PKC) plays key roles in the regulation of signal transduction and cellular function in various cell types. At least ten PKC isoforms have been identified and intracellular localization and trafficking of these individual isoforms are important for regulation of enzyme activity and substrate specificity. PKC can be activated downstream of Gq-protein coupled receptor (GqPCR) signaling and translocate to various cellular compartments including plasma membrane (PM). Recent reports suggested that different types of GqPCRs would activate different PKC isoforms (classic, novel and atypical PKCs) with different trafficking patterns. However, the knowledge of isoform-specific activation of PKC by each GqPCR is limited. α1-Adrenoceptor (α1-AR) is one of the GqPCRs highly expressed in the cardiovascular system. In this study, we examined the isoform-specific dynamic translocation of PKC in living HEK293T cells by α1-AR stimulation (α1-ARS). Rat PKCα, βI, βII, δ, ε and ζ fused with GFP at C-term were co-transfected with human α1A-AR into HEK293T cells. The isoform-specific dynamic translocation of PKC in living HEK293T cells by α1-ARS using phenylephrine was measured by confocal microscopy. Before stimulation, GFP-PKCs were localized at cytosolic region. α1-ARS strongly and rapidly translocated a classical PKC (cPKC), PKCα, (<30 s) to PM, with PKCα returning diffusively into the cytosol within 5 min. α1-ARS rapidly translocated other cPKCs, PKCβI and PKCβII, to the PM (<30 s), with sustained membrane localization. One novel PKC (nPKC), PKCε, but not another nPKC, PKCδ, was translocated by α1-AR stimulation to the PM (<30 s) and its membrane localization was also sustained. Finally, α1-AR stimulation did not cause a diacylglycerol-insensitive atypical PKC, PKCζ translocation. Our data suggest that PKCα, β and ε activation may underlie physiological and pathophysiological responses of α1-AR signaling for the phosphorylation of membrane-associated substrates including ion-channel and transporter proteins in the cardiovascular system.

Ocular Toxicity Assessment From Systemically Administered Xenobiotics

The eye is a unique sensory structure, which must be evaluated for toxicity to determine the safety of drugs, industrial chemicals, and consumer products. Changes in the structure and/or function of ocular tissues following systemic administration of a potential new drug in preclinical animal models can result in significant delays in the development of a new therapeutic and in some cases lead to termination of the development. The ability to detect and characterize ocular toxicity in preclinical models and to predict risk in patients is critically dependent on the preclinical testing strategy, the availability and use of state-of-the-art ocular safety assessment tools, and the knowledge of drug mechanism of action and the current regulatory environment. This review describes the design and execution of toxicity studies with the incorporation of current methods for in vivo assessment of ocular toxicity, including methods for detecting early changes in the eye. In addition, anatomical differences among laboratory animals, preparation of globes for examination, and iatrogenic and spontaneous ocular findings are described that can affect interpretation of toxicological findings. Finally, the correlation between nonclinical outcomes and clinical evaluations is discussed in terms of expected therapeutic uses, indications, and regulatory consequences of ocular effects.

The floppy iris syndrome - what urologists and ophthalmologists need to know

INTRODUCTION

Benign prostatic hyperplasia (BPH) and cataract formation are common in older people. Medical management of symptomatic BPH is often preferred to surgical treatment as surgery increases the risk of morbidities, whereas, surgery is the main form of treatment to restore sight in patient with cataract. The clinical treatment of BPH is either alpha-1 adrenergic antagonist alone or combination of alpha reductase inhibitor and alpha adrenergic receptor (AR) antagonist. There are four alpha-AR antagonists currently available to treat BPH. The uroselective alpha-blocker tamsulosin is the most commonly used drug among all. Studies showed that the majority of the patients who develop intraoperative floppy iris syndrome (IFIS) were on tamsulosin. Women are more likely to develop cataract than men and some recent studies showed that tamsulosin is effective in treating female lower urinary tract symptoms and thereby can cause IFIS during cataract surgery.

EVIDENCE ACQUISITION

We performed a critical review of the published articles and abstracts on association of IFIS with alpha-blockers and other medications as well as other medical conditions.

EVIDENCE SYNTHESIS

Tamsulosin is the most common cause of formation of IFIS. However, not all patients given tamsulosin develop IFIS and cases have been reported without any tamsulosin treatment.

CONCLUSION

Tamsulosin is a recognized cause to impede mydriasis and lead to IFIS during cataract surgery. Urologist should collaborate with their ophthalmology colleagues and general practitioner during prescribing tamsulosin in patients with history of cataract or waiting for planned cataract surgery. The increasing life expectancy and growth of older people will increase the number of men and women who suffer from lower urinary tract symptoms as well as cataract. Therefore, further research and studies are required to properly understand the relation of alpha blockers and IFIS.

The effect of alpha antagonists on pupil dynamics: implications for the diagnosis of intraoperative floppy iris syndrome

PURPOSE

To assess pupil dynamics quantitatively in relation to the use of α1-adrenoceptor antagonists, which contribute to the features of intraoperative floppy iris syndrome, using a new, hand-held, digital pupillometer.

DESIGN

Prospective case-control study.

METHODS

We studied 15 and 25 patients administered tamsulosin and alfuzosin, respectively, as well as 25 control patients. Resting pupil diameter and subsequent contraction, latency, constriction velocity, and dilation velocity were recorded using an electronic pupillometer. All pupil measurements were performed before and after pharmacologic dilation.

RESULTS

In predilation pupillary measurements, we detected a significant decrease in maximum pupillary diameter by 0.50±0.19 mm (P=.011) and in the mean percentage of diameter reduction after stimulation (5.23±2.42%, P=.035) in the tamsulosin group. Alfuzosin also induced a significant decrease in maximum pupillary diameter (0.49±0.17 mm, P=.005). Constriction velocity was significantly reduced by 0.70±0.20 m/s (P=.001) in the tamsulosin group and by 0.54±0.18 m/s (P=.004) in the alfuzosin group. In terms of postdilation measurements, maximum and minimum pupil diameters were reduced significantly only in the tamsulosin group (by 1.09±0.31 mm [P=.001] and by 0.89±0.36 mm [P=.016], respectively).

CONCLUSIONS

We describe a reliable, accurate, and rapid method to acquire quantitative pupil measurements and identify the tendency for intraoperative floppy iris syndrome before cataract surgery after the use of alfuzosin and tamsulosin. This investigation also analyzed the similarities and differences induced by the 2 drugs in predilation and postdilation pupil dynamics, demonstrating that tamsulosin is more potent than alfuzosin in inducing intraoperative floppy iris syndrome.

Alpha antagonists and intraoperative floppy iris syndrome: A spectrum

Background

To determine occurrence of features of intraoperative floppy iris syndrome (IFIS) during cataract surgery in patients taking systemic alpha-antagonists (AA).

Methods

We prospectively studied patients on AA and who underwent phacoemulsification. The following were recorded: pupil diameter preoperatively, iris flaccidity, iris prolapse and peroperative miosis.

Results

We studied 40 eyes of 31 subjects. Mean age was 78 years. Overall, 14 eyes (13 patients) showed signs of IFIS: 9/13 (69%) eyes of patients on tamsulosin, 1/18 (6%) eyes in the doxazosin group, 2/2 prazosin patients, 1/4 eyes in the indoramin group, and 1/2 eyes in two patients on a combination of doxazosin and tamsulosin. Most cases (92%) had only one or two signs of IFIS. Bilateral cataract surgery was undertaken in 9 patients but only one patient (on tamsulosin) had features of IFIS in both eyes, while 4 patients (2 on tamsulosin and 2 on other AA) showed signs of IFIS in one eye only, and 4 patients did not show IFIS in either eye.

Conclusion

Most AA were associated with IFIS, but it tends to present as a spectrum of signs rather than full triad originally described. Tamsulosin was most likely to be associated with IFIS; however, its intake does not necessarily mean that IFIS will occur. For patients on AA, the behavior of the iris intraoperatively in one eye is a poor predictor of the other eye. Surgeons should anticipate the occurrence of IFIS in any patient on AA.

The effect of alpha1-adrenergic receptor antagonist tamsulosin (Flomax) on iris dilator smooth muscle anatomy

PURPOSE

To characterize and determine the effect of tamsulosin (Flomax) on the human iris dilator muscle anatomy.

DESIGN

Retrospective, case-control study.

PARTICIPANTS

This study comprised 51 cadaveric eyes from 27 patients (14 with a history of tamsulosin use and 13 control patients) who underwent autopsy at the Duke University Medical Center, Durham, North Carolina.

METHODS

Patients' records were reviewed, and age, medical, surgical, and ocular history; gender; medications; and duration and dosage of tamsulosin were recorded. Specimens were sectioned through the pupillary axis in the horizontal meridian and reviewed by light microscopy. A morphometric analysis was performed to measure the maximum and minimum iris dilator muscle thickness and the iris stromal thickness (micrometers) at 6 points in each eye. All microscopic evaluations and measurements were performed by the same masked observer.

MAIN OUTCOME MEASURES

To determine whether there is a significant difference in the iris dilator muscle or stromal thickness in those patients receiving tamsulosin treatment compared with age-matched controls.

RESULTS

The mean iris dilator muscle thickness in the tamsulosin-treated group (6.53+/-1.99 microm) was significantly thinner compared with that of the control group (8.50+/-1.61 microm) (P=0.006). There was no difference in iris stromal thickness between the 2 groups (P=0.268). There was no direct relationship between duration of tamsulosin use and iris dilator muscle or stromal thickness. Statistical significance was maintained when the iris dilator muscle thickness was compared between the groups using history of diabetes and cataract extraction as separate variables. No difference was noted when comparing the iris stromal thickness using diabetes as a separate variable. However, stromal thickness was significantly different between the groups in pseudophakic eyes (P=0.005).

CONCLUSIONS

According to histologic examination of cadaver eyes, patients receiving tamsulosin treatment exhibited decreased iris dilator muscle thickness compared with control patients. There was no difference noted in the iris stromal thickness within the groups. We believe this finding may shed light on the pathophysiology of intraoperative floppy iris syndrome. Further studies need to be performed to assess the significance of this histologic finding.

The forefront for novel therapeutic agents based on the pathophysiology of lower urinary tract dysfunction: alpha-blockers in the treatment of male voiding dysfunction - how do they work and why do they differ in tolerability?

alpha(1)-Adrenoceptor antagonists are the mainstay of medical treatment of male voiding dysfunction which typically is attributed to benign prostatic hyperplasia. While original concepts have assumed that they relieve voiding dysfunction by relaxing prostatic smooth muscle, newer data indicate that their therapeutic effects at least partly occur independent of prostatic relaxation, perhaps involving direct effects on blood vessels, urothelium, afferent nerves, and/or smooth muscle of the urinary bladder. The adverse event profiles differ among alpha(1)-adrenoceptor antagonists, with tamsulosin having a particularly good cardiovascular tolerability. While this was originally attributed to its selectivity for alpha(1A)-adrenoceptors, it appears that alfuzosin which lacks subtype-selectivity, has a very similar tolerability. In contrast, doxazosin and terazosin, which are chemically and pharmacologically more closely related to alfuzosin than to tamsulosin, appear to have more side effects attributable to the cardiovascular system. More recent data indicate that tolerability differences between alpha(1)-adrenoceptor antagonists may at least partly relate to pharmacokinetic rather than to pharmacodynamic differences. Taken together, these data emphasize the idea that concepts about drug efficacy and tolerability despite being highly plausible may not necessarily be true and always require thorough experimental testing.

Management of benign prostatic hyperplasia with silodosin

It has been reported that blockade of α1A-adrenoceptor (AR) relieves bladder outlet obstruction, while blockade of α1D-AR is believed to alleviate storage symptoms due to detrusor overactivity. Silodosin, (-)-1-(3-hydroxypropyl)-5-[(2R)-2-({2-[2-(2,2,2trifluoroethoxy) phenoxy]ethyl}amino)propyl]-2,3-dihydro-1H-indole-7- carboxamide, is a new α1A-AR selective antagonist. Silodosin is highly selective for the α1A-AR subtype, showing an affinity for the α1A-AR that is 583- and 55.5-fold higher than its affinity for the α1B-and α1D-ARs, respectively. In randomized, double-blind, placebo-controlled phase III studies performed in Japan and the United States, silodosin has been shown to be effective for both storage and voiding symptoms associated with benign prostatic hyperplasia. Early effects of silodosin (after 2-6 hours or day 1) on lower urinary tract symptoms have also been reported. In urodynamic studies, detrusor overactivity disappeared in 40% and improved in 35% of patients after administration. In pressure flow studies, the grade of obstruction on the International Continence Society nomogram showed improvement in 56% of patients. The rate of adverse events in the silodosin, tamsulosin and placebo groups was 88.6%, 82.3%, and 71.6%, respectively. The most common adverse event was (mostly mild) abnormal ejaculation (28.1%). However, few patients (2.8%) discontinued silodosin because of abnormal ejaculation. Orthostatic hypotension showed a similar incidence in the silodosin (2.6%) and placebo (1.5%) groups. In conclusion, silodosin improves detrusor overactivity and obstruction and thus may be effective for both storage and voiding symptoms in patients with benign prostatic hyperplasia.

Silodosin: an orally active selective α1-adrenoceptor antagonist for benign prostatic hyperplasia

α1-adrenoceptor antagonists play a central role in the treatment of uncomplicated symptomatic benign prostatic hyperplasia, frequently in combination with the 5-α-reductase inhibitors such as finasteride and dutasteride. Clinically useful examples include alfuzosin, doxazosin, tamsulosin and terazosin. These can be subdivided into nonselective (doxazosin and terazosin) and uroselective (alfuzosin and tamsulosin) agents. In general, these agents appear to be equieffective. However, they can be distinguished on the basis of their adverse event profiles. Such adverse events include those due to their vasodilatory effects (dizziness, orthostatic hypotension and rhinitis), genitourinary effects (ejaculatory dysfunction) and nonspecific effects (e.g., asthenia, malaise and gastrointestinal upset). A new α1A-adrenoceptor antagonist, silodosin, has recently been approved. In most ways, it is similar to tamsulosin in its pharmacodynamic effects in vitro and in vivo (in both animals and humans). Limited clinical trial data have shown silodosin to significantly improve lower urinary tract symptoms associated with benign prostatic hyperplasia and quality of life, with effects sustainable for at least 1 year. Its adverse-event profile reflects that seen with other uroselective α-adrenoceptor antagonists with the exception of a relatively high-incidence rate of ejaculatory dysfunction (22 vs 2% with tamsulosin and 28 vs 1% with placebo). This article reviews the preclinical and clinical data concerning silodosin and introduces the reader to this new drug for the treatment of benign prostatic hyperplasia.

The Effects of Systemic Alpha-1 Adrenergic Antagonists on Pupil Diameter in Rats

PURPOSE

To investigate the effects of alpha-1 adrenergic blockers on pupil diameter (PD) in rats.

METHODS

Four groups, with 10 rats each, were designed to receive terazosin, tamsulosin, doxazosin, and no medication. Dilated pupil diameter (PD) measurements were performed 24 hr before, 24 hr after, and 30 days after the initiation of medication, and after 30 days of washout. The intergroup and intragroup differences in PD were evaluated using one-way ANOVA and Wilcoxon signed rank test, respectively.

RESULTS

In day 1, PD decreased in both eyes significantly only in tamsulosin and doxazosin groups, but these effects became insignificant at 30 days of treatment (p > 0.05). The control group showed no significant difference in PD (p > 0.05). PD values returned to baseline after the washout period in all groups.

CONCLUSIONS

A significant reduction in PD occurred in two of the three groups with alpha-1 adrenergic blockers (tamsulosin and doxazosin), but this effect was not sustained at 30 days. Further functional and structural studies of the iris are needed to determine the clinical significance of these findings.

Medical therapy options for aging men with benign prostatic hyperplasia: focus on alfuzosin 10 mg once daily

Lower urinary tract symptoms suggestive of benign prostatic hyperplasia (LUTS/BPH) are common in aging men and can significantly affect quality of life. Men with bothersome LUTS/BPH often present with various other age-related conditions, including sexual dysfunction, heart disease, hypertension, diabetes, and the metabolic syndrome, which can complicate management decisions. Therefore, healthcare providers should be familiar with first-line treatment options for LUTS/BPH and their differing safety profiles, particularly with respect to cardiovascular and sexual function side effects. This article presents a review of first-line medical therapy options for managing aging men with LUTS/BPH and patient considerations when evaluating and selecting these therapies, with a focus on the clinical efficacy and cardiovascular and sexual function safety profiles of the uroselective alpha1-adrenergic receptor antagonist alfuzosin 10 mg once daily. Alfuzosin improves LUTS, peak urinary flow rates, and disease-specific quality of life, reduces the long-term risk of overall BPH progression, and is well tolerated in aging men, with minimal vasodilatory and sexual function side effects, even in those with comorbidities. Alfuzosin is well tolerated when used in combination with antihypertensive medications and phosphodiesterase type 5 inhibitors for the treatment of erectile dysfunction. The long-term clinical efficacy and good cardiovascular and sexual function safety profile of alfuzosin can contribute to an improved quality of life for aging men with LUTS/BPH.

Alpha1-adrenoceptor subtypes and lower urinary tract symptoms

Benign prostatic hyperplasia (BPH) is a common cause of urinary outflow obstruction in aging men leading to lower urinary tract symptoms (LUTS). alpha(1)-Adrenoceptors (alpha(1)ARs) antagonists (blockers) have become a mainstay of LUTS treatment because they relax prostate smooth muscle and decrease urethral resistance, as well as relieving bladder LUTS symptoms. A review of key recent clinical trials suggests new insights into the role of specific alpha(1)AR subtypes in the treatment of LUTS.

Intraoperative floppy-iris syndrome associated with α1-adrenoreceptors

PURPOSE

To compare the incidence of intraoperative floppy-iris syndrome (IFIS) in men exposed to tamsulosin and men exposed to alfuzosin and evaluate the effect of IFIS on the complication rate of cataract surgery.

SETTING

Tertiary care hospital, Chicoutimi, Quebec, Canada.

METHODS

The medical charts of 64 men (92 eyes) who had phacoemulsification cataract surgery between June 2005 and July 2006 and reported having used tamsulosin or alfuzosin at their initial visit for cataract evaluation were reviewed. The presence or absence of IFIS, potential confounding clinical covariates, duration of surgery, and complications were noted. The history of taking an alpha1-antagonist was verified. To address the main objective of the study, only patients who had exclusively used tamsulosin or alfuzosin were included. For the secondary objective, all eligible patients were included even if they had received more than one alpha1-antagonist in the past.

RESULTS

Of men exclusively exposed to tamsulosin (22) or alfuzosin (13), 86.4% and 15.4%, respectively, developed IFIS (P<.001). The adjusted odds ratio of IFIS in patients exposed to tamsulosin compared to those exposed to alfuzosin was 32.15 (95% confidence interval, 2.74-377.11). Eyes with IFIS had a higher risk for complications (focal iris stromal atrophy, transient postoperative hypertension, major iris trauma, posterior capsule break with vitreous loss, zonular dehiscence, postoperative cystoid macular edema) than eyes without IFIS (P<.001).

CONCLUSIONS

Men exposed to tamsulosin had a significantly higher risk for developing IFIS than men exposed to alfuzosin. Intraoperative floppy-iris syndrome significantly increased the complication rate of cataract surgery.

The effects of two systemic α1-adrenergic blockers on pupil diameter: a prospective randomized single-blind study

Our aim was to investigate the effects of two alpha(1)-adrenergic blockers-tamsulosin and alfuzosin-on pupil diameter (PD). In this prospective randomized single-blind clinical trial, 64 patients with benign prostatic hyperplasia received treatment with either tamsulosin or alfuzosin. The same ophthalmologist, masked to the given medication, evaluated patients prior to, 4 weeks after and 6 months after the start of the medication (day 0, day 28 and month 6). Best corrected visual acuity and PD under mesopic, scotopic, and dilated conditions were measured. t-test, ANOVA, and Dunnett's multiple comparison post-test were used for statistical analysis. With tamsulosin treatment, both mesopic and scotopic PD decreased, respectively, from 3.9 +/- 0.7 and 5.7 +/- 0.6 mm at day 0 to 3.6 +/- 0.9 and 5.5 +/- 0.8 mm at day 28, and 3.6 +/- 0.7 and 5.4 +/- 0.7 mm at month 6 (ANOVA; P = 0.021 and = 0.040, respectively). However, the difference in dilated PD was not significant (day 0 7.8 +/- 0.6 mm, day 28 7.7 +/- 0.7 mm, and month 6 7.6 +/- 0.6 mm, P = 0.379). In the alfuzosin group, PD did not differ significantly from the baseline except for the scotopic measurements, which decreased from 5.6 +/- 0.6 mm at day 0 to 5.5 +/- 0.6 mm at day 28 and 5.2 +/- 0.8 mm at month 6 (P = 0.004). Compared to baseline values, small but statistically significant decreases were detected in mesopic and scotopic illumination in patients treated with tamsulosin and in scotopic PD in patients treated with alfuzosin. The clinical significance of these differences needs further evaluation.

α1-Adrenergic Receptor Antagonists and the Iris: New Mechanistic Insights into Floppy Iris Syndrome

Understanding the role of adrenergic receptors in iris biology has gained widespread interest due to the recently described intraoperative floppy iris syndrome sometimes encountered during cataract surgery. alpha(1)AR-mediated iris dilator smooth muscle contraction occurs via alpha(1a)ARs whereas alpha(1b)ARs mediate iris arteriolar contraction. Because alpha(1)AR antagonists are first-line therapy for benign prostatic hyperplasia and lower urinary tract symptoms, more elderly patients requiring cataract surgery now receive these drugs. After reviewing intraoperative floppy iris syndrome, strengths/weaknesses of supporting data, and reviewing iris biology, a case is made that rather than being drug specific (alpha(1)AR antagonists), intraoperative floppy iris syndrome may represent the "tip of the iceberg." Relaxed iris dilator muscle resistant to adrenergic agonists should be expected with clinical drugs shown to relax the iris dilator (e.g., antagonists at alpha(1)AR, endothelin-A, angiotensin receptors, nitric oxide donors such as nitrates), and/or diseases associated with endothelial dysregulation (e.g., congestive heart failure, diabetes, hypertension). Rather than a rare, unexpected, unpredictable syndrome due to one drug, a careful medical history should elucidate intraoperative floppy iris syndrome predisposition. Just as anticoagulants are discontinued prior to elective surgery, conservative management of elderly patients suggests discontinuation of drugs that relax iris dilator muscle, in consultation with the patient's primary physician, should be considered prior to cataract surgery.