Cialis (Tadalafil) Dosing for Young Adults Ages 18 to 29

What dose does a man in his 20s start on?

The Cialis label starts as-needed treatment at 10 mg taken before anticipated sexual activity, then the dose is increased to 20 mg or decreased to 5 mg based on efficacy and tolerability, with a maximum frequency of once per day [1]. For once-daily use in ED, the starting dose is 2.5 mg taken at about the same time every day, without regard to the timing of sexual activity, and it may be increased to 5 mg [1].

Drugs@FDA lists the 5, 10 and 20 mg Cialis tablets as prescription and lists the 2.5 mg tablet as discontinued [2]. The label says not to split Cialis tablets and to take the entire dose, and that Cialis may be taken with or without food [1].

Does being 18 to 29 change the dose?

The label's ED regimens are not written as separate doses for younger men. The populations it adjusts for are people with reduced kidney function, people with liver impairment, and people taking CYP3A4 inhibitors or alpha-blockers [1].

The trials behind those regimens enrolled mostly older men. In the eight 12-week placebo-controlled as-needed studies the mean age was 59, with a range of 22 to 88 [1]. An integrated analysis of five 12-week as-needed trials covered 1,112 men with a mean age of 59 and a range of 22 to 82 [3]. These results include men as young as 22 but do not provide a separate dosing estimate for men aged 18 to 29.

On-demand versus once daily

With as-needed use, a 5 to 20 mg dose is taken before sex and no more than once a day [1]. The label says Cialis improved erectile function compared with placebo for up to 36 hours after a dose; it does not cause an erection on its own, and sexual stimulation is still required [1]. Peak blood levels arrive between 30 minutes and 6 hours after a dose, with a median of 2 hours [1].

With once-daily use, 2.5 mg (or 5 mg) is taken at about the same time every day regardless of when sex happens [1]. Steady state is reached within 5 days, and exposure at steady state is about 1.6 times that of a single dose, so once-daily dosing gives continuous blood levels [1]. The mean terminal half-life is about 17.5 hours in healthy subjects [1].

Kidney, liver and drug interactions that lower the dose

These apply at any adult age, so a 24-year-old on ritonavir, ketoconazole or an alpha-blocker is dosed differently from a 24-year-old on nothing.

Kidney function. With creatinine clearance 30 to 50 mL/min, as-needed use starts at 5 mg with a maximum of 10 mg not more often than every 48 hours; below 30 mL/min or on hemodialysis the maximum is 5 mg not more often than every 72 hours, and once-daily use is not recommended below 30 mL/min [1].

Liver function. In mild or moderate impairment (Child-Pugh A or B) the as-needed dose should not exceed 10 mg; in severe impairment (Child-Pugh C) Cialis is not recommended [1].

CYP3A4 inhibitors. With drugs such as ketoconazole or ritonavir, as-needed use is capped at 10 mg every 72 hours and once-daily use at 2.5 mg [1]. Ketoconazole 400 mg daily raised tadalafil 20 mg exposure (AUC) by 312% and peak concentration by 22%, and ritonavir 200 mg twice daily raised AUC by 124% [1]. Erythromycin, itraconazole and grapefruit juice were not studied, and the label says they would likely raise exposure [1].

Alpha-blockers. For ED, a man already stable on an alpha-blocker starts tadalafil at the lowest dose; for BPH the label does not recommend combining the two, because efficacy has not been adequately studied and blood pressure can drop [1]. With doxazosin 8 mg daily, tadalafil 20 mg produced a placebo-subtracted maximal standing systolic fall of 9.8 mm Hg [1].

What to watch for

In the eight 12-week as-needed studies, headache occurred in 11% on 10 mg and 15% on 20 mg versus 5% on placebo, dyspepsia in 8% and 10% versus 1%, back pain in 5% and 6% versus 3%, myalgia in 4% and 3% versus 1%, nasal congestion in 3% versus 1%, and flushing in 3% versus 1% [1]. Discontinuation for adverse events was 3.1% on 10 or 20 mg versus 1.4% on placebo [1]. Back pain and myalgia usually began 12 to 24 hours after a dose and resolved within 48 hours [1].

In healthy volunteers, tadalafil 20 mg lowered supine blood pressure by a mean maximal 1.6/0.8 mm Hg versus placebo [1]. The label says ED drugs including Cialis should not be used by men for whom sexual activity is inadvisable because of cardiovascular status [1].

The label says an erection lasting more than 4 hours, painful or not, needs emergency care, and painful erections over 6 hours can permanently damage erectile tissue [1]. It says sudden vision loss in one or both eyes may be non-arteritic anterior ischemic optic neuropathy (NAION) and to stop Cialis and seek medical attention [1]. Two observational case-crossover studies suggested roughly a 2-fold risk (estimates 2.15, 95% CI 1.06 to 4.34, and 2.27, 95% CI 0.99 to 5.20), and the label states that neither those studies nor the postmarketing reports establish a causal relationship [1]. Cialis should be used with caution, and only when the anticipated benefits outweigh the risks, in men with a history of NAION, and is not recommended in hereditary retinal disorders such as retinitis pigmentosa [1]. Sudden hearing decrease or loss has been reported, possibly with tinnitus and dizziness; the label says to stop and seek prompt medical attention, and that a direct link cannot be determined [1].

Nitrates and alcohol

Any form of organic nitrate, taken regularly or intermittently, is contraindicated with Cialis [1]. The label says that in a life-threatening situation where a nitrate is medically necessary, at least 48 hours should pass after the last Cialis dose, and the nitrate is then given only under close medical supervision with hemodynamic monitoring [1]. In a 150-man crossover study, sublingual nitroglycerin 0.4 mg given after 7 days of tadalafil 20 mg daily still pushed standing systolic pressure below 85 mm Hg in more men than placebo at 4, 8 and 24 hours, with no difference at 48, 72 and 96 hours [4]. That is an emergency rule, not a spacing schedule for routine use, and the authors concluded the two should not be combined [4].

Alcohol and tadalafil are both mild vasodilators. Five units or more with Cialis can increase orthostatic signs and symptoms, including a faster heart rate, lower standing blood pressure, dizziness and headache [1]. Tadalafil did not change alcohol levels and alcohol did not change tadalafil levels [1]. Combining Cialis with another PDE5 inhibitor or another ED treatment has not been studied [1].

Testosterone

The label reports no adverse effect of tadalafil 10 or 20 mg on mean testosterone, luteinizing hormone or follicle-stimulating hormone concentrations compared with placebo [1]. Cialis is approved for ED and BPH, not low testosterone [1]. Adcirca is a separate tadalafil product approved for pulmonary arterial hypertension [5].

If 20 mg does not work

Twenty milligrams once a day is the top of the as-needed range [1], so there is no higher approved step. Peak levels come at a median of 2 hours but can take as long as 6 hours, and food does not change absorption [1].

The label says evaluation of erectile dysfunction should include an appropriate medical assessment to identify potential underlying causes, as well as treatment options [1]. That matters in this age group. In a series of 439 consecutive men seeking first medical help for new ED, 114 (26%) were 40 or younger, with a mean age of 32.4 and a range of 17 to 40; 90.4% of the younger men had no other medical conditions on the Charlson index versus 58.3% of older men, and the younger group smoked and used illicit drugs more often [6].

Getting tadalafil

Drugs@FDA lists Cialis tablets as prescription products. FDA approved Cialis for ED on 21 November 2003 under NDA 021368, and a supplement dated 6 October 2011 added the BPH indication [2]. HealthRX.com offers tadalafil by prescription.