Intraoperative floppy iris syndrome

Dealing with floppy iris syndrome

PURPOSE OF REVIEW

The aim of this study was to review and summarize recent findings and advancements regarding intraoperative floppy iris syndrome (IFIS). Although many improvements have been made for the management of IFIS, it remains a challenging condition for surgeons. An understanding of the syndrome as well as the multitude of tools to mitigate risk of complication is important for surgeons operating on high-risk patients.

RECENT FINDINGS

A variety of management approaches have been modified and improved or further supported with new data, such as intracameral compounds, intraoperative devices and surgical techniques.

SUMMARY

An understanding of risk factors is important for the identification of at-risk patients. A variety of approaches can greatly reduce incidence of IFIS complications. Multiple management strategies should be utilized to further reduce risk during these difficult surgeries.

Predictive value of pupillography on intraoperative floppy iris syndrome in preoperative period

AIM

To present the frequency of intraoperative floppy iris syndrome (IFIS) in cataract patients who taking alpha 1-a receptor antagonist (ARA) drugs, and evaluate the predictive value of pupil diameter (PD) changes in IFIS patients.

METHODS

Male cataract patients who are under treatment with alpha-1a-ARAs (alfuzosin, tamsulosin) intraoperatively were evaluated and were grouped as with/without IFIS. The preoperative PD values were compared with controls. Also, the intraoperative manipulations and early/late complications were recorded.

RESULTS

A total of 77 patients (77 eyes) of 94 benign prostate hyperplasia (BPH) patients have been defined as IFIS (81.91%) and 40 patients (40 eyes) were taking tamsulosin and 37 patients (37 eyes) were taking alfuzosin. During the cataract surgery, the rate of posterior capsular rupture (P=0.754), vitreous loss (P=0.585), iris tears (P=0.004), and iris catching (P=0.000) were higher in IFIS group, but the difference was significant only in the iris catching. At the postoperative first-month visit, persistent IOP rise and iris stromal tears were more frequent in IFIS group, but the difference was not significant (P=0.311, P=0.146; respectively). In contrast, Descemet membrane detachment was insignificantly more frequent in controls (P=0.311). In IFIS and control patients, PDs were 9.54±1.78 and 9.72±1.57 mm (P=0.255) under scotopic illumination, 8.54±1.43 and 8.74±1.25 mm (P=0.289) under mesopic illumination, 6.99±1.35 and 7.27±1.39 mm (P=0.662) under photopic illumination, respectively. However PDs were lower in IFIS under all illumination degrees, no significant difference was detected between groups.

CONCLUSION

IFIS is a significant clinical syndrome with an increased intraoperative/postoperative complication ratio. The prediction of this syndrome is important because of prevention required precautions against possible complications. There is no association between IFIS and preoperative PD.

Ocular Side Effects of Common Systemic Medications and Systemic Side Effects of Ocular Medications

When prescribing medications, it is important to consider the ocular side effects of common systemic therapy as well as potential systemic side effects of ocular medications. Although not an exhaustive list of medications/classes of medications, this article does include many commonly used drugs and also provides information on some topical therapies commonly used by ophthalmologists. These ocular medications may result in systemic effects and/or alter patients' management of systemic conditions.

Intraoperative Floppy Iris Syndrome Induced by Tamsulosin: The Risk and Preventive Strategies

Tamsulosin is an antagonist of a subtype-specific alpha-1A- and alpha-1D-adrenoceptor (AR) that is expressed in the prostate gland, urethra, and bladder. Several reports have shown a possible relationship between ophthalmologic adverse effects and the use of alpha-1-receptor medicines, including tamsulosin. This descriptive review evaluates the intraoperative floppy iris syndrome (IFIS) associated with tamsulosin. A search of the Medline and PubMed databases was conducted to identify control trials, case reports, and observational examinations published in English. The publication dates were restricted (January 1, 2000, to January 1, 2020). Keywords (tamsulosin, alpha-blocker, ocular, eye, adverse reaction, and IFIS) were used in the searches. The searches identified 66 studies including in vitro or in vivo studies, trials, and observational studies. Twenty-two (33.33%) studies were articles citing tamsulosin and IFIS as having confirmed potential risk to ocular safety. The results of this review, including a comprehensive summary of published research on tamsulosin use in different populations, have identified several articles showing associations between tamsulosin and IFIS that merit further investigation. Suspending of potential causative pharmacological treatment of IFIS before ocular surgery including tamsulosin, proper identification of at-risk patients, preoperative prophylaxis treatments, and surgical technique modifications clearly can mitigate the anticipated risk of IFIS induced by tamsulosin.

Modified Corneal Incisions for Cataract Surgery in Patients Treated with Tamsulosin: A Prospective Study

PURPOSE

To evaluate modified anterior elongated corneal incisions as a simple technique to reduce the incidence and severity of intraoperative floppy iris syndrome (IFIS), in patients taking tamsulosin (a selective α_1a-adrenergic receptor antagonist).

METHODS

This prospective case series was conducted at Meir Medical Center, a tertiary care facility in Israel. Included were 45 eyes of 39 male patients taking tamsulosin, and thus prone to IFIS. Patients underwent phacoemulsification cataract surgery with anterior elongated corneal incisions. The primary outcomes were the incidence and severity of IFIS, the complication rate and the need for additional IFIS management techniques. The secondary outcome was to quantify the surgically induced astigmatism, using Alpin's vector analysis. The tamsulosin treatment period and pupil diameter during five stages of the surgery were also noted.

RESULTS

The overall rate of IFIS was 33.33% (n = 15). The IFIS severity was rated as mild in 22.22% and moderate in 11.11% of the study eyes. No IFIS was noted in 66.67% of the eyes. There were no cases of severe IFIS, and no need for other IFIS management strategies. The complications rate was 2.22% (n = 1). Patients who developed IFIS had a significantly smaller pupil at the beginning of surgery (p < 0.05). There was no significant difference in tamsulosin treatment period between patients with and without IFIS (p = 0.19). The centroid - the mean SIA vector was 0.51 D @ 18° ±1.5 D (SD).

CONCLUSIONS

In tamsulosin treated patients, using modified corneal incisions may be feasible in order to reduce the incidence and severity of IFIS during cataract surgery. Future randomized studies are warranted.

One-day postoperative intraocular pressure spikes after phacoemulsification cataract surgery in patients taking tamsulosin

PURPOSE

To evaluate the relationship between 1-day postoperative intraocular pressure (IOP) after phacoemulsification cataract surgery and tamsulosin use.

SETTING

University of Colorado Health Eye Center, Aurora, Colorado, USA.

DESIGN

Retrospective cohort study.

METHODS

Registry data from men who had cataract surgery were used. Patients taking tamsulosin at the time of surgery were included as cases, while patients with no history of tamsulosin use were used as controls. The primary outcome was a 1-day postoperative IOP spike defined as an IOP increase greater than 10 mm Hg compared with baseline or a 1-day postoperative IOP of 30 mm Hg or higher. General estimating equations were used for analysis.

RESULTS

The study comprised 584 men (864 eyes). An IOP increase greater than 10 mm Hg or IOP 30 mm Hg or higher after cataract surgery occurred in 12.4% and 9.3%, respectively, of eyes in the tamsulosin group versus 4.4% and 2.1%, respectively, in the control group (all P = .001). After adjusting for significant covariates, patients on tamsulosin were 2.6 times (95% confidence interval [CI], 1.2-5.7; P = .01] and 3.8 (95% CI, 1.3-10.9; P = .01) more likely to have a 1-day postoperative IOP increase greater than 10 mm Hg or a 1-day postoperative IOP of 30 mm Hg or higher.

CONCLUSION

Patients on tamsulosin had an increased risk of a 1-day postoperative IOP spike after cataract surgery, showing the importance of identifying patients on tamsulosin preoperatively to better manage and potentially mitigate IOP spikes.

FINANCIAL DISCLOSURE

None of the authors has a financial or proprietary interest in any material or method mentioned.

Numerical stress analysis of the iris tissue induced by pupil expansion: Comparison of commercial devices

Purpose

(1) To use finite element (FE) modelling to estimate local iris stresses (i.e. internal forces) as a result of mechanical pupil expansion; and to (2) compare such stresses as generated from several commercially available expanders (Iris hooks, APX dilator and Malyugin ring) to determine which design and deployment method are most likely to cause iris damage.

Methods

We used a biofidelic 3-part iris FE model that consisted of the stroma, sphincter and dilator muscles. Our FE model simulated expansion of the pupil from 3 mm to a maximum of 6 mm using the aforementioned pupil expanders, with uniform circular expansion used for baseline comparison. FE-derived stresses, resultant forces and area of final pupil opening were compared across devices for analysis.

Results

Our FE models demonstrated that the APX dilator generated the highest stresses on the sphincter muscles, (max: 6.446 MPa; average: 5.112 MPa), followed by the iris hooks (max: 5.680 MPa; average: 5.219 MPa), and the Malyugin ring (max: 2.144 MPa; average: 1.575 MPa). Uniform expansion generated the lowest stresses (max: 0.435MPa; average: 0.377 MPa). For pupil expansion, the APX dilator required the highest force (41.22 mN), followed by iris hooks (40.82 mN) and the Malyugin ring (18.56 mN).

Conclusion

Our study predicted that current pupil expanders exert significantly higher amount of stresses and forces than required during pupil expansion. Our work may serve as a guide for the development and design of next-generation pupil expanders.

[Pharmacotherapy of urinary incontinence in the elderly]

The prevalence and the incidence of Urinary Incontinence is growing. Women suffer predominantly from stress and mixed urinary incontinence and men from urge incontinence. In elderly people, the pathophysiological and the physiological change in the lower urinary tract system must be considered as well as an underlying multimorbidity. Stress urinary incontinence is among others caused by an insufficient urethral closure mechanism and urge incontinence is followed by unhibited detrusor contractions. Medical treatment is beside other important conservative options only one part of the treatment strategy in incontinence. Duloxetine, a serotonine-norepinephrine reuptake inhibitore can increase activity of the external urethral sphincter and is able to reduce incontinence episodes in up to 64 %. Antagonists of muscarinic receptors can reduce urgency, frequency and urge incontinence as well as increase bladder capacity significantly. In Germany, darifenacin, fesoterodin, oxybutynin, propiverine, solifenacin, tolterodine and trospium chloride are available to treat urge incontinence. The efficacy of these agents are almost comparable in the elderly with the exception of oxybutynin IR. However, tolerability is different and not well studied in the elderly population with the exception of fesoterodin. Side effects, especially dry mouth, dizziness and constipation often limit their use. None of the agents show ideal efficacy or tolerability in all patients. Last summer therefore a β3-agonist mirabegron was also introduced in Germany but was withdrawn.

Pupil Dilation with Intracameral Epinephrine Hydrochloride during Phacoemulsification and Intraocular Lens Implantation

Objective. To investigate mydriatic effect of intracamerally injected epinephrine hydrochloride during phacoemulsification and intraocular lens (IOL) implantation. Methods. Eighteen cataract patients for bilateral phacoemulsification were enrolled. To dilate pupil, one eye was randomly selected to receive intracamerally 1 mL epinephrine hydrochloride 0.001% for 1 minute after corneal incision (intracameral group), and the contralateral eye received 3 drops of compound tropicamide 0.5% and phenylephrine 0.5% at 5-minute intervals 30 minutes before surgery (topical group). Pupil diameters were measured before corneal incision, before ophthalmic viscoelastic device (OVD) injection, after OVD injection, before IOL implantation, and at the end of surgery. Results. At each time point, the mean pupil diameter in the intracameral group was 2.20 ± 0.08, 5.09 ± 0.20, 6.76 ± 0.19, 6.48 ± 0.18, and 5.97 ± 0.24 mm, respectively, and in the topical group it was 7.98 ± 0.15, 7.98 ± 0.15, 8.53 ± 0.14, 8.27 ± 0.16, and 7.93 ± 0.20 mm, respectively. The topical group consistently had larger mydriatic effects than the intracameral group (P < 0.05). The onset of mydriatic effect was rapid in the intracameral group. There was no difference in surgical performance or other parameters between groups. Conclusions. Intracameral epinephrine hydrochloride appears to be an alternative to the mydriatic modalities for phacoemulsification and IOL implantation. In comparison with topical mydriatics, intracameral epinephrine hydrochloride offers easier preoperative preparation, more rapid pupil dilation, and comparable surgical performance.

The differential pupillary response to 2.5% phenylephrine in patients taking tamsulosin

PURPOSE

To determine if a pharmacological test could be developed to determine iris dilator dysfunction in patients taking tamsulosin.

METHODS

Patients taking tamsulosin and controls were recruited from the Urology and Ophthalmology clinics at the Montefiore Medical Center. The patient's right eye (OD) was dilated with phenylephrine hydrochloride 2.5% and tropicamide 1%. The patient's left eye (OS) was dilated with tropicamide 1% alone. Forty minutes after dilation, pupillary diameter was measured in both eyes.

RESULTS

Thirty-eight tamsulosin subjects and 43 controls met the inclusion criteria for the study. The tamsulosin-treated patients dilated less with phenylephrine than controls (0.61±0.4 vs. 1.10±0.45 mm, respectively P<0.001). Receiver operating characteristic curves comparing maximal pupillary dilation versus differential pupillary dilation in tamsulosin patients relative to controls shows a greater area under the curve for differential dilation (0.8 vs. 0.6, respectively). A correlation between smooth muscle dysfunction and length of time on tamsulosin was observed. Patients using tamsulosin for <1 month had an average OD-OS difference of 0.85±0.5 mm. Patients who were on tamsulosin for >1 month had an average OD-OS difference of 0.52±0.32 mm (P<0.01, Mann-Whitney).

CONCLUSION

Patients treated with tamsulosin demonstrated a significantly decreased iris dilatory response to the selective adrenergic effects of phenylephrine compared to controls. Additionally, it appears that longer duration of exposure to tamsulosin increases the likelihood of dilator dysfunction.

The effects of tamsulosin and alfuzosin on iris morphology: an ultrasound biomicroscopic comparison

CONTEXT

It is well known that Alpha-1 adrenergic receptor antagonists affect the receptors in the prostate and also iris dilator muscle, leading to loss of iris muscle tone.

OBJECTIVE

To compare morphological alterations of iris secondary to tamsulosin and alfuzosin use.

PARTICIPANTS

Patients included in the study were grouped as follows: 16 patients treated with tamsulosin (Group 1), 14 patients treated with alfuzosin (Group 2) and 18 untreated controls (Group 3).

MATERIALS AND METHODS

All patients underwent ultrasound biomicroscopic and pupillometric examination. Iris thickness was measured at the dilator muscle region (DMR; measured at half of the distance between the scleral spur and the pupillary margin) and sphincter muscle region (SMR; Standardized at 0.75 mm from the pupillary margin). DMR/SMR was also calculated for each patient. Differences among groups were analysed. Main outcome measures were DMR, SMR, DMR/SMR and pupillary diameter.

RESULTS

Mean duration of treatments were 2.4 ± 0.96 years (1-4) and 2.3 ± 1.01 years (1-4) in Groups 1 and 2. Pupillary diameters were reduced in Groups 1-2 compared to Group 3 (p < 0.001, p < 0.001). The SMR was similar in Groups 1 and 2 (p: 0.114). These values were not significantly different from that of Group 3 (p: 0.196, p: 0.209). However, thickness in the DMR in Groups 1-2 were significantly lower than that of controls (Group 3) whereas there was no significant difference between Groups 1 and 2 (p: 0.041, p: 0.039 and 0.986, respectively). Mean DMR/SMR ratios were significantly lower in Groups 1-2 than that of Group 3 (p: 0.040 and p: 0.040, respectively).

CONCLUSIONS

In patients using these medications, the iris seems to be thinner at the dilator muscle region, but preserving the sphincter muscle region.

Quantitation of in vitro α-1 adrenergic receptor antagonist binding capacity to biologic melanin using tandem mass spectrometry

PURPOSE

The purpose of this study was to develop methods to allow evaluation of the binding characteristics for a series of α-1 antagonists to biologically-derived melanin.

METHODS

Fresh bovine globes were used to obtain iridal and choroid/retinal pigment epithelial (CRPE) derived melanin. Binding characteristics of chloroquine, tamsulosin and doxazosin were then evaluated in vitro using tandem mass spectroscopy.

RESULTS

Tandem mass spectrometry-based assays were developed for three α-1 antagonists that provided linear assay ranges which spanned (minimally) 0.01-10 µg/mL, while exhibiting excellent inter-assay precision and accuracy. When applied to the evaluation of binding characteristics for iridal melanin, mean chloroquine and tamsulosin fractions were found to be 41.9 ± 14.2 pmoles mg(-1) and 25.34 ± 6.186 pmoles mg(-1), respectively. Mean iridal doxazosin binding was found to be 6.36 ± 2.19 pmoles mg(-1). Interestingly, mean levels of tamsulosin, but not doxazosin found bound to choroid/CRPE derived melanin approached that of chloroquine (27.91 µg/mL, 25.68 µg/mL and 5.94 µg/mL for chloroquine, tamsulosin and doxazosin, respectively). One way ANOVA for binding affinity for chloroquine, tamsulosin and doxazosin was statistically significant for both iridal and CRPE-derived melanin (p = 0.0012 and 0.0023), respectively. A Bonferroni post-hoc analysis demonstrated a statistically significant difference in the amount of binding between tamsulosin, doxazosin and chloroquine to iridal but not CRPE derived melanin (p < 0.05).

CONCLUSIONS

Tamsulosin appears to demonstrate melanin binding affinity which approaches chloroquine and exceeds doxazosin for both iridal and CRPE-derived bovine melanin.

Intraoperative floppy-iris syndrome

OBJECTIVE

Intraoperative-floppy iris syndrome (IFIS) has been recently described. It has been demonstrated that this new syndrome complicates cataract surgery. In this paper we have reviewed the syndrome, and offer practical information specially related to the origin and management of this syndrome and we offer practical information.

MATERIAL AND METHODS

A review of the related medical literature using PubMed and Cochrane databases. Combining the search terms tamsulosin, cataract, IFIS and intraoperative floppy iris syndrome, more than 200 articles were found. Eighty-two of them were obtained and analysed. In the remaining only the abstract could be studied.

RESULTS

The aetiological association between IFIS and tamsulosin (and to a lesser degree between IFIS and other alpha-antagonists) is well established. Other aetiological associations are doubtful. Most of the literature is centred on cataract surgery. However, a similar syndrome has been described during trabeculectomy. A possible association between these drugs and choroidal detachments has also been described. Undoubtedly tamsulosin treatment makes cataract surgery more difficult and increases the probability of intraoperative complications. Protocols to manage the syndrome have not yet been developed. Intracameral injection of alpha-adrenergic agonists seems to be useful. However there is no evidence of the usefulness of discontinuing the drug or using preoperative mydriatics.

CONCLUSION

The aetiological and clinic features of the syndrome are well established. More studies are needed to provide scientific evidence on the most appropriate way to cope with this syndrome.

Management of intraoperative iris prolapse: stepwise practical approach

Iris prolapse is not an uncommon occurrence during cataract surgery. It usually occurs through the main incision during hydrodissection and is commonly associated with floppy-iris syndrome; however, it can manifest in cases with no known predisposition and can occur at any stage during surgery. The mechanism is explained by the Bernoulli principle and its effect on iris position during the movement of fluid within the eye. Predisposing factors are iris configuration, anterior chamber depth, and position and architecture of the corneal tunnel. Strategies for prevention and management include the use of pharmacological agents, ophthalmic viscosurgical devices, and iris retractors. These strategies can be augmented by alteration and adaptation of the surgeon's technique.

Cataract surgery in patients taking alpha-1 antagonists: know the risks, avoid the complications

BACKGROUND

The growing use of alpha-1 receptor antagonists in the treatment of benign prostatic hyperplasia (BPH) has created a new problem in ophthalmic surgery, the so-called intraoperative floppy iris syndrome (IFIS). This consists of a billowing iris, insufficient pupillary dilation with progressive intraoperative miosis, and protrusion of iris tissue through the tunnel and side port incision that are made for access to the anterior chamber during surgery. IFIS presents particular difficulties in cataract surgery which is carried out through the pupil with manipulations in the immediate vicinity of the iris. The complications range from poor visibility of the operative field to iris damage with the surgical instruments and to rupture of the posterior capsule, with loss of lens material into the vitreous body.

METHODS

Selective literature review.

RESULTS

Alpha-blockers have a direct effect on the alpha-receptors of the iris but also induce ultrastructural changes in the iridial stroma, leading to IFIS. The most important factor in avoiding complications of IFIS seems to be the ophthalmic surgeon's knowledge that the patient is taking an alpha-1 receptor antagonist.

CONCLUSION

A thorough medical history and an optimized information flow among all physicians treating the patient-the urologist, the family physician, and the ophthalmic surgeon-are essential for safe cataract surgery.

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.

Benign prostatic hyperplasia. Clinical treatment can complicate cataract surgery

PURPOSE

To investigate the effects of alpha-1 adrenergic receptor antagonists for the treatment of benign prostatic hyperplasia (BPH) regarding potential risks of complications in the setting of cataract surgery.

AIM

To address recommendations, optimal control therapy, voiding symptoms and safety within the setting of cataract surgery.

MATERIALS AND METHODS

A comprehensive literature review was performed using MEDLINE with MeSH terms and keywords "benign prostatic hyperplasia", "intraoperative floppy iris syndrome", "adrenergic alpha-antagonist" and "cataract surgery". In addition, reference lists from identified publications were reviewed to identify reports and studies of interest from 2001 to 2009.

RESULTS

The first report of intraoperative floppy iris syndrome (IFIS) was observed during cataract surgery in patients taking systemic alpha-1 AR antagonists in 2005. It has been most commonly seen related to use of tamsulosin. Changes of medication and washout periods of up to 2 weeks have been attempted to reduce the risk of complications in the setting of cataract surgery.

CONCLUSION

Patients under clinical treatment for BPH should be informed about potential risks of this drug class so that it can be discuss with their healthcare providers, in particular urologist and ophthalmologist, prior to cataract surgery.

Silodosin: a selective alpha1A-adrenergic receptor antagonist for the treatment of benign prostatic hyperplasia

BACKGROUND

Silodosin is a new alpha(1)-adrenergic receptor antagonist that is selective for the alpha(1A)-adrenergic receptor. It was approved by the US Food and Drug Administration (FDA) in 2008 for the treatment of lower urinary tract symptoms (LUTS) associated with benign prostatic hyperplasia (BPH).

OBJECTIVE

This article reviews the pharmacology, pharmacokinetics, clinical efficacy, adverse effects, drug interactions, and dosage and administration of silodosin in adult male patients with BPH.

METHODS

A search of MEDLINE (1950-October 8, 2009), International Pharmaceutical Abstracts (1970-October 8, 2009), and the Iowa Drug Information Service database (1966-October 8, 2009) was conducted using the terms silodosin, KMD-3213, benign prostatic hyperplasia, and alpha(1)-adrenergic receptor antagonist. Reports of research and review articles published in English were identified and evaluated, and the bibliographies of these articles were reviewed for additional relevant publications. A search of the FDA Web site was performed, and abstracts and posters presented at scientific meetings of the American Urological Association were reviewed.

RESULTS

By antagonizing alpha(1A)-adrenergic receptors in the prostate and urethra, silodosin causes smooth muscle relaxation in the LUT. Silodosin has greater affinity for the alpha(1A)-adrenergic receptor than for the alpha(1B)-adrenergic receptor (by a factor of 583), minimizing the propensity for blood pressure-related adverse effects mediated by alpha(1B) blockade. In 3 controlled clinical studies in patients with BPH-related LUTS (1 published; 2 presented in the prescribing information and published in a pooled analysis), patients receiving silodosin at a total daily dose of 8 mg had significant improvements in the International Prostate Symptom Score (IPSS) and maximum urinary flow rate (Q(max)) compared with those receiving placebo (both, P < 0.05). The most commonly reported adverse effect was abnormal or retrograde ejaculation (>22%), and the incidence of orthostatic hypotension was low (<3%).

CONCLUSIONS

In the small number of clinical trials reviewed, silodosin was associated with significant reductions in IPSS and Q(max) compared with placebo. To determine whether silodosin's selectivity for the alpha(1A)-adrenergic receptor translates into a clinical advantage relative to other available agents, long-term studies evaluating the comparative efficacy and tolerability of silodosin and other alpha(1)-blockers (specifically tamsulosin) are necessary.