Cialis (Tadalafil) Missed-Dose Protocol: What to Do and When to Skip

What the Cialis label says about daily dosing

Cialis is a PDE5 inhibitor indicated for erectile dysfunction (ED), the signs and symptoms of benign prostatic hyperplasia (BPH), and both conditions together [1].

Once-daily use is written three ways: 2.5 mg once daily for ED, which may be increased to 5 mg; 5 mg once daily for BPH, taken at approximately the same time every day; and 5 mg once daily for ED with BPH, also at approximately the same time every day [1]. The label says Cialis may be taken with or without food and that the tablets are not to be split; the entire dose is taken [1]. Drugs@FDA lists the Cialis 2.5 mg tablet as discontinued [2].

As-needed use is a different schedule: a starting dose of 10 mg before anticipated sexual activity, adjustable between 5 and 20 mg, with a maximum of once per day [1]. There is no fixed clock time; an as-needed dose is taken before activity, so there is no scheduled daily dose to miss.

The dosing section does not describe what to do after a forgotten daily tablet, and it does not describe taking a second tablet to replace one [1].

How tadalafil levels behave between doses

Tadalafil reaches peak concentration between 30 minutes and 6 hours after a dose (median 2 hours) and has a mean terminal half-life of 17.5 hours in healthy subjects [1]. Once-daily dosing reaches steady state within 5 days, at an exposure about 1.6-fold that of a single dose, and the label says once-daily use provides continuous plasma tadalafil levels [1].

Nitrates and other timing rules

Organic nitrates in any form are contraindicated with Cialis [1]. The label says that in a life-threatening situation where a nitrate is medically necessary, a nitrate may be considered only after at least 48 hours have elapsed since the last Cialis dose, under close medical supervision with hemodynamic monitoring [1]. In a 150-man crossover study, men took tadalafil 20 mg or placebo daily for 7 days and then sublingual nitroglycerin 0.4 mg; standing systolic blood pressure fell below 85 mm Hg in more men on tadalafil at 4, 8 and 24 hours, with no difference at 48, 72 and 96 hours [3].

The label says an erection lasting more than 4 hours, painful or not, needs emergency care, and that sudden vision loss in one or both eyes or a sudden decrease or loss of hearing calls for stopping Cialis and getting medical care [1].