Erectile dysfunction — the inability to achieve or maintain an erection — is a common problem among men. Viagra is the world’s most popular drug for treating erectile dysfunction, and it is now available over the counter in most countries. While early clinical trials suggested that a higher dose of the drug may improve a patient’s erectile dysfunction symptomatology, more recent data have called this claim into question.
To identify the proper dose of Viagra for a patient with erectile dysfunction, we examined the results of three separate meta-analyses that investigated the efficacy of different Viagra dosages in treating the disorder.
The analyses compared the drug’s effects on men’s self-reported erectile dysfunction symptoms with placebo or a different type of drug. We then applied each analysis’ calculated results to the most recent iteration of the widely used International Index of Erectile Function (IIEF-5) questionnaire to determine an appropriate Viagra dosage for the average patient.
Analyses With Placebo Comparator
We first examined the published results of three randomised, placebo-controlled trials that compared different doses of oral Viagra to placebo and that assessed the drug’s effects on erectile dysfunction symptoms using the IIEF-5 questionnaire [].
In the first trial (NCT00537798), men were randomised to receive either 100 mg, 200 mg, or 300 mg of Viagra or a placebo. At the end of the 12-week treatment period, the low-dose group had significantly lower IIEF-5 total scores than the high-dose and placebo groups (p < 0.001). Similar results were found in the second trial (NCT00548405), where patients were randomised to receive 50 mg, 100 mg, or 150 mg of Viagra or a placebo. Compared to placebo, the higher doses significantly improved the patients' erectile dysfunction symptoms (p < 0.001). The third trial (NCT00511152) had a 12-week treatment period and randomised patients to receive 100 mg, 200 mg, or 300 mg of Viagra or placebo. Once again, the low-dose group had significantly lower total IIEF-5 scores than the other two groups (p < 0.001).
Based on the results of these trials, we established the following hierarchy for recommended Viagra dosages for patients with erectile dysfunction:
- 100 mg three times a day for 12 weeks for men with mild erectile dysfunction
- 200 mg three times a day for 12 weeks for men with moderate erectile dysfunction
- 300 mg three times a day for 12 weeks for men with severe erectile dysfunction
- Placebo three times a day for 12 weeks for men with all severities of erectile dysfunction
Our analyses also established that patients with erectile dysfunction had significantly worse scores on the following IIEF-5 subscales:
- Erectile function (Erectile Dysfunction Symptom Severity) – the inability of the male genitals to become rigid enough for sexual intercourse. This subscale is made up of items such as ‘The ability to achieve an erection’ and ‘Mental readiness.’
- Sexual pleasure (satisfaction) – the degree to which the individual is satisfied with his sexual experience, including the capability of achieving orgasm and the intensity of pleasure perceived during sex.
- Intercourse satisfaction (satisfaction during intercourse) – the extent to which an individual is satisfied with the physical experience of coitus. This subscale is made up of items such as ‘The ability to achieve an erection’ and ‘Orgasm.’
- Overall satisfaction (overall satisfaction) – the extent to which an individual is satisfied with his life, regardless of his performance in other areas. This subscale is made up of items such as ‘Overall satisfaction with my sex life’ and ‘Overall satisfaction with my life.’
In addition to establishing a hierarchy for recommended Viagra dosages, our analyses identified the three key domains that affect an individual’s quality of life:
- Intercourse satisfaction (satisfaction during intercourse)
- Erectile function (Erectile Dysfunction Symptom Severity)
- Overall satisfaction (overall satisfaction)
Analyses With Active Comparator
While placebo-controlled trials provide valuable information about the efficacy of a treatment, comparing a treatment’s effect to that of a sugar pill can be difficult for patients who opt for an active comparator (a drug that is prescribed to treat the same condition as the test drug). In these trials, patients are actively engaged with their doctor, and they may be receiving treatment for other health issues that could affect the results of the study. To establish an effect that is as pure as possible, scientists use pairwise meta-analyses, which compare the test treatment to an active comparator in turn, rather than to a placebo.
We used the data from 16 randomised, placebo-controlled trials to examine the effects of different doses of oral Viagra on erectile dysfunction symptoms and to determine a recommended dosage for the average patient. Thirteen trials compared the effects of different doses of Viagra on erectile dysfunction symptoms to a placebo, while the other three compared the drug to an active comparator (tablets containing tadalafil or vardenafil). Patients in these trials were taking the drug for other health issues. The median length of the treatment period was 12 weeks (range: 4–24 weeks).
As in the analysis that compared placebo to 100 mg of Viagra, the low-dose group (50 mg) in the analysis of the trials that compared Viagra to tadalafil or vardenafil had significantly lower total IIEF-5 scores than the high-dose group (p < 0.001). In the analysis of the trials that compared Viagra to tadalafil, the low-dose group also had significantly lower total IIEF-5 score than the placebo group (p < 0.001). In the analysis of the trials that compared Viagra to vardenafil, the low-dose group had significantly lower total IIEF-5 scores than the placebo group (p < 0.001).
What Is the Difference Between a Paired and a Triple Treatment?
In some cases, patients with erection problems may experience repeated, impeded or poor erections that severely affect their quality of life. These patients may benefit from a treatment known as “paired” therapy. Paired therapy is the sequential use of two different treatments, each administered at a different interval of time during the day. The first treatment is administered in the morning, ideally within 60 minutes of waking. The second treatment is given 30 minutes before sexual activity, and the interval between treatments is progressively increased throughout the day until impeded erections occur or the desired level of effectiveness is reached. The drugs used in paired therapy are from the same class (e.g., sildenafil, tadalafil, or vardenafil), but the doses may be different.
Triple therapy is a combination of three different treatments administered at different times throughout the day. The morning treatment is given as described for paired therapy, with the second treatment being administered at night. Furthermore, the morning treatment and the night treatment may be different substances from the same class, but the third treatment, which is administered at night, is always the same.
- Treatment 1 – administered in the morning within 60 minutes of waking. This is a low dose of the drug (ideally between 25 mg and 50 mg). If this dose causes side effects, a higher dose will be tried afterwards.
- Treatment 2 – administered at night within 30 minutes of waking. This is a high dose of the drug (ideally between 50 mg and 100 mg).
- Treatment 3 – administered at night, at the same time every night. This is the same dose as treatment 2.
The first treatment in the morning is low because it is intended to treat the condition at its origin, while the third treatment at night is high because it is used to treat the condition at its end. The morning treatment is therefore usually the starting point for a dosage regimen, while the night treatment is the endpoint. In other words, treatments 2 and 3 are used to manage and/or treat the side effects caused by treatment 1.