Sildenafil (Generic) for Adults 65+: Transitioning to and Managing Care in Older Patients

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What actually changes after 65

For erectile dysfunction, sildenafil has no effect without sexual stimulation [1]. What changes with age is exposure. In healthy men 65 and older, sildenafil AUC was about 84% higher than in younger men [1]. The Viagra label gives 50 mg as the usual adult dose, allows adjustment to 100 mg or down to 25 mg, caps use at once per day, and says to consider a 25 mg start for patients over 65 because higher plasma levels were seen in these patients [1].

The label's geriatric section notes that 18% of men in Viagra's clinical studies were 65 or older and 2% were 75 or older, and that no overall difference in safety or efficacy appeared between older and younger men. It still recommends considering 25 mg, since higher plasma levels may increase the incidence of adverse reactions [1].

Timing numbers are worth knowing. Peak levels arrive 30 to 120 minutes after a fasting dose; a high-fat meal delays the peak by about 60 minutes and lowers peak concentration by 29% [1]. The terminal half-life is about 4 hours for sildenafil and for its active N-desmethyl metabolite, which carries about 50% of the parent drug's PDE5 potency and about 20% of the effect [1].

Kidney and liver function add to the age effect. In severe renal impairment (creatinine clearance below 30 mL/min) exposure roughly doubles and the label suggests starting at 25 mg [1]. In Child-Pugh A or B hepatic impairment, peak concentration was 47% higher and AUC 85% higher, again with a suggested 25 mg start; Child-Pugh C has not been studied [1].

Cardiovascular risk before the first dose

The label's first safety point is not about milligrams. Sexual activity carries cardiac risk, and the label says erectile dysfunction treatments including Viagra should not generally be used in men for whom sexual activity is inadvisable because of cardiovascular status [1].

Sildenafil lowers blood pressure modestly. A single 100 mg dose in healthy volunteers produced a mean maximum supine fall of about 8.4/5.5 mm Hg, and between 25 and 100 mg the effect was not dose-related [1]. The label lists situations with no controlled data: a myocardial infarction, stroke or life-threatening arrhythmia within the last 6 months; resting blood pressure below 90/50 or above 170/110; cardiac failure; or unstable angina. If prescribed in those circumstances, the label says to do so with caution [1]. Caution also applies to left ventricular outflow obstruction such as aortic stenosis and to severely impaired autonomic control of blood pressure [1].

Antihypertensives add to the drop. Viagra 100 mg taken with amlodipine 5 or 10 mg in hypertensive patients produced an additional mean supine reduction of 8/7 mm Hg [1].

The Second Princeton Consensus Conference sorted men with cardiovascular disease into low, intermediate and high risk categories for sexual activity and reviewed the safety of sildenafil, tadalafil and vardenafil in that population [4].

Nitrates: the contraindication that does not change with age

Any nitric oxide donor, meaning organic nitrates or organic nitrites in any form, taken regularly or intermittently, is contraindicated with sildenafil, which potentiates their hypotensive effect [1].

The harder question comes after a dose. The label states plainly that it is unknown when nitrates can safely be given after Viagra [1]. At 24 hours after a 100 mg dose, plasma sildenafil sits near 2 ng/mL against a peak of about 440 ng/mL, but that 24-hour level runs 3 to 8 times higher in men over 65 and in men with liver impairment, severe kidney impairment, or concurrent erythromycin or a strong CYP3A4 inhibitor. The label says it is unknown whether nitrates are safe even at 24 hours [1].

Alpha-blockers and the 25 mg start

Alpha-blockers and sildenafil both lower blood pressure, the effects are additive, and symptomatic hypotension (dizziness, light-headedness, fainting) can occur [1]. The label's instruction is about sequence: the patient should be stable on alpha-blocker therapy before sildenafil is started, and sildenafil should then start at 25 mg [1]. With doxazosin, Viagra 25 mg produced a placebo-subtracted maximum standing systolic fall of 6.0 mm Hg (7.4 mm Hg supine); among 4 men given 100 mg, one had severe postural hypotension [1]. In the reverse direction, if a man is already on an optimized dose of a PDE5 inhibitor, the label says to start the alpha-blocker at its lowest dose [1].

CYP3A4 inhibitors change the dose

Sildenafil is cleared mainly by CYP3A4, with CYP2C9 a minor route [1]. Ritonavir raised sildenafil AUC 11-fold, and with ritonavir the label's maximum is 25 mg in a 48-hour period [1]. Saquinavir raised peak concentration 140% and AUC 210%; erythromycin raised peak concentration 160% and AUC 182%; ketoconazole and itraconazole are expected to have larger effects than saquinavir [1]. With erythromycin or a strong CYP3A4 inhibitor such as saquinavir, ketoconazole or itraconazole, the label says a 25 mg starting dose should be considered [1].

Revatio's label words this differently: strong CYP3A inhibitors are not recommended with it, and moderate-to-strong CYP3A inducers such as bosentan lower sildenafil exposure, so the dose may need up-titration, with a reduction back to 20 mg three times a day when the inducer stops [2].

On alcohol, sildenafil 50 mg given with alcohol to a mean peak blood alcohol of 0.08% did not potentiate alcohol's hypotensive effect in healthy volunteers in the label's interaction study [1].

Revatio and PAH: a different product with a different schedule

Revatio is also sildenafil, but it is a distinct product approved for pulmonary arterial hypertension (WHO Group I) as 20 mg tablets and an injection; the oral suspension approval is marked discontinued [5][2]. For adults, the Revatio label recommends 20 mg orally three times a day, with titration up to 80 mg three times a day based on symptoms and tolerability [2].

In the 12-week SUPER-1 trial, 278 patients with symptomatic PAH were randomized to placebo or sildenafil 20, 40 or 80 mg three times daily; placebo-corrected six-minute walk distance gains were 45 m, 46 m and 50 m (P<0.001 for each) [6]. The Revatio label also flags pulmonary veno-occlusive disease, where the drug is not recommended because of the risk of pulmonary edema, and pulmonary hypertension secondary to sickle cell disease, where a small terminated study reported more vaso-occlusive crises requiring hospitalization on Revatio than on placebo [2]. The Revatio label says patients taking Revatio should not take Viagra or other PDE5 inhibitors, because those combinations have not been studied [2].

Generic sildenafil and combining ED treatments

Viagra is a prescription tablet for erectile dysfunction [7][1]. Generic sildenafil tablets are approved under separate applications, and all sildenafil labels found in the FDA database are prescription-only; no over-the-counter sildenafil product was found.

The Viagra label also says it should not be combined with other PDE5 inhibitors or other erectile dysfunction treatments; such combinations have not been studied and may further lower blood pressure [1].

One review of PDE5 inhibitors noted that in geriatric or difficult-to-treat patients, measuring testosterone helps predict whether any of these drugs will work [8].

How well does it work in older men?

The pivotal 1998 program ran two double-blind studies. In the 12-week flexible-dose study of 329 men, 69% of intercourse attempts were successful on sildenafil versus 22% on placebo, with a mean of 5.9 versus 1.5 successful attempts per month [9].

Age-specific data come from a single-practice series of 167 men over 60, split into 60 to 69, 70 to 79 and 80-plus groups. Overall 54% responded, with a mean gain of 5.7 points on the IIEF erectile function domain. Response rate and IIEF score both fell significantly with age, with the weakest response in men 80 and older. Side-effect rates did not differ across the age groups: headache 18%, flushing 8%, dyspepsia 8%, nasal congestion 5%, visual changes 2% [3]. This was a practice database rather than a randomized trial, so the age gradient is a signal, not a fixed rule.

What to watch for

In flexible-dose trials, the common reactions were headache 16%, flushing 10%, dyspepsia 7%, nasal congestion 4% and abnormal vision 3% (mostly transient color tinge, light sensitivity or blurring), against placebo rates of 4%, 1%, 2%, 2% and 0% [1]. Discontinuation for adverse reactions was 2.5% on Viagra versus 2.3% on placebo in placebo-controlled studies [1].

The label says to stop sildenafil and seek medical care for sudden loss of vision in one or both eyes, which may be non-arteritic anterior ischemic optic neuropathy (NAION) [1]. Observational case-crossover studies suggest an approximate 2-fold increase in NAION risk with PDE5 inhibitor use (risk estimates 2.15, 95% CI 1.06 to 4.34, and 2.27, 95% CI 0.99 to 5.20), while the label states that neither post-marketing reports nor these studies substantiate a causal relationship; it gives the annual incidence of NAION as 2.5 to 11.8 cases per 100,000 in men 50 and older, and advises caution in men with previous NAION or a crowded optic disc [1].

Sudden decrease or loss of hearing, sometimes with tinnitus and dizziness, has been reported in temporal association with PDE5 inhibitors, and the label says to stop and seek prompt medical attention [1]. The label says an erection lasting more than 4 hours needs immediate medical help; a painful erection over 6 hours is priapism, and untreated it can cause permanent loss of potency. Caution applies with penile deformity such as Peyronie's disease and with sickle cell anemia, multiple myeloma or leukemia [1]. Sildenafil offers no protection from sexually transmitted infections [1].