Early sildenafil dose optimization and personalized instruction improves the frequency, flexibility, and success of sexual intercourse in men with erectile dysfunction


We investigated the effect of early sildenafil dose optimization and personalized instructions on sexual intercourse success in 1109 men beginning sildenafil therapy for erectile dysfunction. In phase 1 (4 weeks), patients followed the instructions contained in the sildenafil (50 mg) sample pack and had 1.4 sexual intercourse attempts per week with 82% success. Patients (17%) had a second intercourse attempt (80% successful): 58% occurred within 4 h, 20% within 5–8 h, and 22% within 9–24 h of the first attempt. In phase 2 (4 weeks), sildenafil was adjusted as needed (53% to 100 mg, and 2% to 25 mg), and investigators provided personalized instructions to facilitate patient success. Sexual intercourse attempts increased to 1.7 per week, with 91% success, and 18% were followed by a second attempt, of which 91% were successful. Most patients requested the 100-mg dose, which helped improve sexual intercourse frequency, flexibility and success.


Erectile dysfunction (ED) is estimated to affect 13–28% of men aged 40–80 years, and the prevalence is expected to increase as the population ages.1 The inability to achieve and maintain a hard erection for satisfactory sexual function can place a significant emotional burden on the patient and his partner. The World Health Organization includes maintenance of physical, emotional and social well-being as important components of overall health.2 The psychosocial consequences of ED may include low confidence and poor self-esteem, and a significant negative impact on successful sexual intercourse, a satisfying sexual experience and marital relationships.3

Of the available treatment options for ED, oral sildenafil citrate is non-invasive, well tolerated, and efficacious.4 Sildenafil provides reliable, hard erections, and is preferred to more invasive treatment options by the majority of ED patients.5, 6 In addition, recent research suggests that, by improving erectile function (EF), sildenafil may improve measures of self-esteem, confidence and sexual relationship satisfaction.7, 8 Moreover, for men with ED, satisfaction with sexual relationships is positively and significantly correlated with their EF and the frequency of achieving an erection sufficient for sexual intercourse.9

The dosing instructions in the Viagra Sample Pack are designed to provide the greatest efficacy for the majority of men. A starting dose of 50 mg is recommended for most men with ED.10 However, a proportion of men may discontinue treatment because they do not respond to either the first prescribed dose or they do not properly follow the provided dosing instructions.11 In a meta-analysis of 10 randomized, double-blind, placebo-controlled clinical trials, the discontinuation rate for patients prescribed sildenafil was only 10%,12 compared with 35–45% for men with ED receiving sildenafil in a clinical practice setting.13, 14 The better treatment adherence rates observed in clinical trials may be due to better initial instructions on the use of the medication and to better follow-up with treatment. Other reasons for treatment discontinuation may include lack of emotional readiness for the restoration of sexual life, comorbid diseases or medications, or lack of sexual interest.13, 14 For men who do not initially respond to their first dose of sildenafil, but wish to continue using sildenafil, several studies have shown that increasing their dose to 100 mg and re-educating them on the proper use of sildenafil may improve treatment response, satisfaction and adherence.11, 12

Better understanding of sildenafil dosing and administration information may help men achieve better success and satisfaction when treatment is initiated with sildenafil. Therefore, we designed a study to investigate the impact of sildenafil dosage and the use of the Viagra Sample Pack instructions on the treatment of ED. In this report, we focus on sexual intercourse frequency, flexibility and treatment success achieved with sildenafil.


We investigated whether the Sample Pack instructions for sildenafil conveys sufficient dosage and administration information for flexibility of use, satisfaction and successful sexual intercourse in men beginning therapy for ED with sildenafil. We also investigated the impact of dose optimization and personalized administration instructions on treatment satisfaction and measured the frequency and success rate of sexual intercourse attempts within 24 h of taking sildenafil in men with ED.


Study design

This was an 8-week, multicenter, open-label, flexible-dose study of sildenafil (25, 50 and 100 mg, PRN) that was conducted in two phases. Patients completed the International Index of Erectile Function (IIEF)15 at baseline to determine their severity of ED.16 In the first 4-week phase, patients were given sildenafil (50 mg) and were instructed to follow the dosing instructions provided in the Viagra Sample Pack without further clarification (Table 1). Patients were asked to maintain an event log of sexual activity, which was subsequently used to determine the timing, number and success rate of sexual intercourse attempts. At week 4, patients completed the Erectile Dysfunction Inventory of Treatment Satisfaction (EDITS)17 and the IIEF. Satisfaction rate was defined as the percentage of patients responding to the EDITS question 1, which asks ‘Overall, how satisfied are you with this treatment?’ that they were ‘very’ or ‘somewhat’ satisfied with treatment. For patients who responded other than ‘very satisfied’ to question 1 of the EDITS, investigators were instructed to ask open-ended questions, such as ‘Why were you dissatisfied?’ Based on the patient's response, the investigators could adjust the sildenafil dose to 25 or 100 mg for efficacy and tolerability, and provided recommendations to improve treatment satisfaction. After an additional 4 weeks of treatment with sildenafil, patients again completed the EDITS and IIEF.

Table 1 Information provided to patients in the VIAGRA (sildenafil citrate) sample package

Inclusion criteria

All patients were 18 years of age, had a clinical diagnosis of ED, were in a stable relationship, and had never taken a phosphodiesterase 5 inhibitor for the treatment to ED.

Exclusion criteria

Patients who were taking any contraindicated medications, including nitrates or potent CYP3A4 inhibitors, were excluded. Patients were excluded if they had significant cardiovascular disease, including cardiac failure, myocardial infarction, unstable angina, stroke, transient ischemic attack or cardiac arrhythmias. Patients who had had prostate surgery, brachytherapy, or radiation therapy, or were using any ED treatment were also excluded.

Main outcome measure

The primary study objective was to assess patient's satisfaction with sildenafil and to verify that the Viagra Sample Pack conveys sufficient dosage and administration information for appropriate use. Satisfaction rate was defined as the percentage of patients responding to the EDITS question 1 that they were ‘very’ or ‘somewhat’ satisfied with treatment. Reasons for dissatisfaction with treatment were recorded.

Secondary outcome measures

Other study measures included change in scores from baseline to week 4 and week 8 on the EF domain of the IIEF.16 Successful sexual intercourse attempts were determined from patient-kept logs of sexual activity.


This study was conducted in compliance with the investigators' Institutional Review Board/Independent Ethics Committee and in compliance with Good Clinical Practice, including International Conference on Harmonization Guidelines consistent with the Declaration of Helsinki. All patients provided written informed consent. All observed or volunteered adverse events (AEs) were recorded for the duration of the study.



In total, 1109 patients were enrolled and took at least one dose of study medication between 29 September 2003 and 10 June 2004. Patients' mean age was 54±13 years (range=20–87 years), and the mean duration of ED was 3 years (range <1–44 years) (Table 2). A total of 867 (78.2%) patients completed the study protocol. The most common reason for discontinuation was subject default; 196 (18%) of patients were lost to follow-up or refused to continue. In an analysis of the demographic characteristics of these patients, the mean (range) age was 52 years (20–82), mean (range) duration of ED was 2.8 years (<1–43 years), the percentage of patients with organic, psychogenic or mixed ED was 65, 11 and 25%, respectively, and the percentage of patients with severe, mild-to-moderate, moderate, or mild ED was 38, 22, 24 and 9%, respectively, and was not different from study completers.

Table 2 Demographic characteristics of all patients who took study medication

Study outcomes: phase 1

At week 4, the mean rate of sexual intercourse attempts per week was 1.4, and 80% of sexual intercourse attempts that occurred within 24 h of taking sildenafil were successful. On average 17% of intercourse attempts were followed by a second sexual intercourse attempt within 24 h of taking sildenafil, and 80% of second sexual intercourse attempts were also successful. The group of men who made at least one second sexual intercourse attempt (vs those who did not) were generally younger (49±12 vs 57±12) and fewer men had severe ED (23 vs 43%). Most (58%) second attempts occurred within 4 h of the first attempt; 20% within 5–8 h, and 22% within 9–24 h of the first attempt (Figure 1). Patients (75%) replied that they were ‘very’ or ‘somewhat’ satisfied with treatment (question 1 of the EDITS). The overall mean baseline EF domain score was 14.3, indicating moderate ED, and improved by 9.2 points to 23.5 (Table 3). The improvement in mean EF domain scores indicated a shift from moderate ED to mild ED, and suggested an improvement in EF and erection hardness. At baseline 7% of patients reported EF domain scores 26. However, at week four 58% of patients had EF domain scores 26 (Figure 2). The majority of patients achieved a ‘no ED’ level of severity on the IIEF EF domain. Scores on all IIEF domains improved from baseline to the end of the first 4-week phase of treatment with sildenafil.

Figure 1

Percentages and success rate of second sexual intercourse attempts after taking sildenafil. After 4 and 8 weeks of taking sildenafil, patients reported the number of times they had a second sexual intercourse attempt within 24 h of taking sildenafil. The percentages and success rates were calculated from patient-kept logs of sexual activity.

Table 3 Responses to the EDITS and the EF domain of the IIEF at week 4 and week 8
Figure 2

Proportion of men who had EF domain scores 26 at baseline, week 4, and week 8. The percentage of patients who had scores 26 on the EF domain of the IIEF was calculated at baseline, after 4 weeks, and after 8 weeks of receiving sildenafil.

Study outcomes: phase 2

Of the initial 1109 men, 184 patients discontinued treatment because of default, refusal to continue, or were lost to follow-up. Of the 925 men who entered phase 2, 494 (53%) requested an increase in their dose of sildenafil to 100 mg, 416 (45%) remained on the 50-mg dose and 15 (2%) decreased to 25 mg. Patients who chose to increase their sildenafil dose to 100 mg had slightly lower mean baseline scores on the EF domain of the IIEF (13.4 vs 15.2) compared with patients who chose to remain at the 50-mg dose of sildenafil. The average number of sexual intercourse attempts for all patients increased to 1.7 per week, and 91% of attempts within 24 h were successful. The percentage of successful second sexual intercourse attempts increased to 18% and the success rate increased to 91% (Figure 1). Similar to that observed in phase 1, the group of men who made at least one second sexual intercourse attempt (vs those who did not) were younger (50±12 vs 57±12) and had fewer men with severe ED (27 vs 39%). The proportions of attempts at 4 h, between 5 and 8 h, and between 9 and 24 h were 59, 19 and 22%, respectively, and were similar to that observed in phase 1. At baseline 7% of patients reported EF domain scores 26. However, at week 8, 75% of patients had EF domain scores 26 (Figure 2). The percentage of men who were ‘very’ or ‘somewhat’ satisfied increased to 87%, and the mean EF domain score increased to 25.7 (highest possible score=30) (Table 3). All other IIEF domain scores improved further from baseline to the end of phase 2.

At the end of week 4, 196 men were not completely satisfied with sildenafil. Some of the responses to the open-ended question ‘Why were you dissatisfied?’ and the possible personalized instructions they received are shown in Table 4. In addition, doses were adjusted based on efficacy and tolerability. After an additional 4 weeks of treatment, with personalized dose and instructions, 64% of those who were initially not completely satisfied at week 4 became ‘very’ or ‘somewhat’ satisfied at the end of week 8 (Table 3). Whereas patients who were satisfied with treatment in phase 1 achieved a mean EF domain score of 23.5 after the first 4 weeks of treatment, patients who were not satisfied with treatment achieved a mean EF domain score of only 16.6 after the first 4 weeks of treatment. However, following an additional 4 weeks of treatment, and with dose optimization and personalized instructions, their mean EF domain score improved to 26.0 (Table 3). Scores on all domains of the IIEF were lower in this group compared to those of patients who were satisfied with treatment at the end of phase 1. Moreover, the percentage of successful sexual intercourse attempts was also lower, but improved from 51% at the end of phase 1 and to 90% at the end of phase 2.

Table 4 Possible responses for why patients were not completely satisfied and possible personalized instruction to improve efficacy and satisfaction

The correlations between the proportion of men who were satisfied with treatment (EDITS question 1) and four of the five domains of the IIEF were positive, ranging from 0.58 to 0.69. The correlation between EDITS question 1 and the Sexual Desire domain was also positive, but lower (0.32).


In total, 34% of patients experienced AEs, which included headache (12%), flushing (12%), rhinitis (2%) and dyspepsia (2%) and were generally mild and transient in nature. Serious AEs occurred in seven of the 1109 patients who took study medication, but none were related to the study drug. There were no discontinuations due to AEs, and the rate of AEs observed in this study was consistent with that observed from a meta-analysis of randomized controlled trials of sildenafil.12


This study highlights the importance of early dose customization and follow-up instructions for improved treatment success. The study has some limitations. For example, the dropout rate in phase 1 was nearly 18%. The continuing population may conceivably have been more motivated, have had more favorable interpersonal situations, or have had less severe ED. However, in a post hoc analysis of data from patients who defaulted, the demographic characteristics were not different from those of the overall baseline study population. The discontinuation rate is in line with published clinical trials of PDE5 inhibitors and is much lower than in the general population of men using PDE5 inhibitors.12, 13, 14 In addition, this was an open-label study with a fixed treatment sequence. A randomized, parallel study in which one patient population receives standard instruction and the other receives personalized instruction may yield different comparative data and would eliminate the possibility of a period effect.18 However, the current study was designed to reflect real-world experience with sildenafil and the effect of follow-up counseling and dose optimization on intercourse success and treatment satisfaction.

Patients seeking treatment for chronic conditions are frequently not provided proper instruction on how to use their medication. For example, 56% of patients taking SSRIs for depression reported receiving no instructions on taking their medication.19 This may be due in part to the amount of time clinicians spend with patients reviewing dosing and administration instructions. A study of 467 audiotapes and transcripts of outpatient visits revealed that physicians and patients spend an average of 4 min discussing medications.20 Physicians may rely on pharmacists to provide the bulk of medication utilization instruction. A series of surveys conducted from 1982 to 1994 on patients' reports of drug counseling revealed that, over this time period, patient counseling has only increased from 5 to 15% at the physician's office, but from 16 to 59% at the pharmacy.21 In the current study, we tried to mimic the real world scenario of patient counseling at the physician's office. As a result, we found that patients with ED who were naive to PDE5 inhibitors and followed the current Viagra Sample Pack instructions had improved erectile function. Early dose optimization and providing personalized dosing instructions resulted in further improvements in erectile function. In this open-label study, the majority of men with ED achieved EF domain scores indicating ‘no ED,’22 and initial satisfaction with treatment was high. When patients' concerns regarding treatment dissatisfaction were addressed after the first 4-week phase, the satisfaction with treatment was even higher. Adjustments in dosage allowed the majority of men who were initially not satisfied with treatment a second chance to achieve treatment satisfaction and success. The prospective nature of this study adds to previous retrospective studies of patients salvaged with reinstruction, and reveals that 50% of treatment nonresponders can become successful. These results illustrate the importance of proper instructions for patients and emphasize the need for physicians to encourage follow-up visits with their patients to help maximize treatment results and salvage patients who may not be initially satisfied with treatment.

The half-life of sildenafil, about 4 h, has been established from pharmacokinetic studies in healthy men and in men with ED.23, 24 However, recent empirical studies, in which objective and subjective measures of erection hardness and duration of erections were used, revealed a much longer amount of time that men with ED can achieve and maintain an erection of sufficient hardness for having successful sexual intercourse: up to 12 h after a dose of sildenafil.25, 26 We show that the effects of sildenafil can last up to 24 h, much longer than the traditionally recommended 4 h. Although only 18% of men had successful second sexual intercourse at the end of phase 2, a relatively high proportion (>40%) of these men had successful second sexual intercourse attempts more than 4 h after their first sexual intercourse attempt. These men were generally younger with less severe ED than men who did not attempt sexual intercourse for a second time on the same dose. The data suggest that the flexibility in timing for sexual intercourse for these men is substantially longer than was traditionally thought. This extended flexibility may allow some men with ED and their partners to achieve a satisfying sexual experience, which may improve overall relationship quality.7, 8, 9

The physiological and psychological impact of ED can affect measures of a man's and his partner's quality of life. Successful treatment with sildenafil has been shown to boost self-esteem, confidence, and satisfaction with sexual relationship.7, 8, 9 In the current study, more than half of men increased their dose from 50 mg to 100 mg, which may suggest that rapid dose titration could be considered for some men with ED. A higher dose of sildenafil may increase the proportion of men who can achieve and maintain an erection for satisfactory sexual intercourse, which may improve treatment adherence.11, 27


Using early dose optimization and personalized administration instructions, patients may achieve and maintain a high level of treatment efficacy and satisfaction, which may improve the psychosocial impact that ED has on men and their partners.


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This study was funded by Pfizer Inc. Editorial support was provided by Carl Clay, PhD, at Complete Healthcare Communications Inc., and was funded by Pfizer Inc. The authors thank all investigators who contributed to this study: Abraham Morgentaler, MD, Brookline, MA; Robert Lesser, MD, New Orleans, LA; Barton Wachs, MD, Long Beach, CA; Robert Lipetz, MD, San Diego, CA; William Borkon, MD, Minneapolis, MN; Glen Wells, MD, Birmingham, AL; David Mobley, MD, Houston, TX; Donald Kidd, MD, Mobile, AL; Gilbert Dale, MD, Fresno, CA; David Kaufman, MD, New York, NY; Stephen Auerbach, MD, Newport Beach, CA; Marcia Miller, MD, Gainesville, FL; Gordon Brody, MD, Arlington, TX; Gary Oshinksy, MD, Garden City, NY; Han Hanafy, MD, Harrisburg, IL; Emerson Harrison, MD, Decatur, GA; Robert Modarelli, MD, Tacoma, WA; Irving Fishman, MD, Houston, TX; Simon Mirelman, MD, Birmingham, AL; Irvin Hirsch, MD, Philadelphia, PA; Adrian James, MD, New Orleans, LA; James Bailen, MD, Jeffersonville, IN; John Cudecki, MD, Chicago, IL; James McMurray, MD, Huntsville, AL; John Mulhall, MD, New York, NY; Vahan Kassabian, MD, Atlanta, GA; Mark Swierzewski, MD, Tampa, FL; Gary Karlin, MD, Lawrenceville, NJ; Lynn Conrad, MD, Germantown, TN; Albert Canas, MD, Miami Beach, FL; Charles White, MD, Mobile, AL; Martin Dineen, MD, Daytona Beach, FL; Michael O'Leary, MD, Boston, MA; Neil Baum, MD, New Orleans, LA; Brian Roberts, MD, Myrtle Beach, SC; Joseph Banno, MD, Peoria, IL; William Fitch, MD, San Antonio, TX; Robert Gessler, MD, Laurel, MD; Michael Collins, MD, Hoover, AL; Ronald Castellanos, MD, Fort Myers, FL; Rafael Wurzel, MD, New Britain, CT; Robert Salant, MD, New York, NY; Samuel Axelrad, MD, Houston, TX; Stanley Brosman, MD, Marina Del Rey, CA; Fernando Borges, MD, St. Petersburg, FL; Robert Waldbaum, MD, Manhassett, NY; Laurence, Belkoff, DO, Bala Cynwyd, PA; William Jennings, MD, San Antonio, TX; William Monnig, MD, Cincinnati, OH; Walter Pittman, MD, Homewood, AL; Connie Abarikwu, MD, Phoenix, AZ; James Barada, MD, Albany, NY; Winston Barzell, MD, Sarasota, FL; Martin, Bastuba, MD, La Mesa, CA; Teresa, Beam, MD; Indianapolis, IN; Robert Brannigan, MD, Chicago, IL; Joseph Camps, MD, Tallahassee, FL; Stacy Childs, MD, Cheyenne, WY; James Cochran, MD, Dallas, TX; Ronald DeGuerre, MD, St. Louis, MO; Jules Deutsch, MD, Gretna, LA; Craig Donatucci, MD, Durham, NC; Robert Eastridge, MD, Palm Beach Gardens, FL; Robert Feldman, MD, Waterbury, CT; Floyd Freiden, MD, Kansas City, MO; Rene Frontera, MD, St. Clair Shores, MI; Louis Galdieri, MD, West Orange, NJ; Phillip Ginsberg, DO, Philadelphia, PA; Marc Gittelman, MD, Aventura, FL; William Glover, MD, Fairfax, VA; Kenneth Goldberg, Carrollton, TX; Abraham Hawatmeh, MD, St. Louis, MO; Wayne Hellstrom, MD, New Orleans, LA; Stanton Honig, MD, New Haven, CT; David Jablonski, MD, Orlando, FL; Joel Kaufman, MD, Aurora, CO; Ira Klimberg, MD, Ocala, FL; Dean Knoll, MD, Nashville, TN; Michael Lutz, MD, Southfield, MI; Myron Murdock, MD, Greenbelt, MD; Gregory Parr, MD, Port Orange, FL; Arthur Pinto, MD, Trumbull, CT; Steven Promisloff, MD, Hillsboro, OR; Stephen Sacks, MD, Los Angeles, CA; William Scaljon, MD, Atlanta, GA; Robert Sher, MD, Rockville, MD; Ned Stein, MD, Houston, TX; David Talley, MD, San Antonio, TX; William Terens, MD, Edison, NJ; Kevin Tomera, MD, Anchorage, AK; Frank Tortora, MD, Cary, NC; John Tuttle, MD, Lexington, KY; Larry Walker, MD, Memphis, TN; Douglas Ward, MD, Washington, DC; Michael Werner, MD, Purchase, NY; Kenneth Wiley, MD, New Orleans, LA.

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Steidle, C., McCullough, A., Kaminetsky, J. et al. Early sildenafil dose optimization and personalized instruction improves the frequency, flexibility, and success of sexual intercourse in men with erectile dysfunction. Int J Impot Res 19, 154–160 (2007). https://doi.org/10.1038/sj.ijir.3901498

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  • erectile dysfunction
  • sildenafil
  • sexual intercourse success

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