Cialis (tadalafil) comes in four tablet strengths: 2.5 mg, 5 mg, 10 mg, and 20 mg. Which one you’re prescribed depends on whether you’re taking it as needed before sexual activity or once daily, and whether it’s for erectile dysfunction (ED), an enlarged prostate, or both.
As-Needed Dosing for ED
The 10 mg and 20 mg tablets are designed for as-needed use. The typical starting dose is 10 mg, taken before anticipated sexual activity. Based on how well it works and how you tolerate it, your prescriber may increase it to 20 mg or lower it to 5 mg. The maximum frequency is once per day, regardless of the strength.
Cialis reaches peak levels in the blood at a median of about 2 hours after you take it, though the range is anywhere from 30 minutes to 6 hours. What sets it apart from other ED medications is its duration: a single dose can improve erectile function for up to 36 hours. That long window is why it’s sometimes called “the weekend pill,” and it means you don’t need to time the dose as precisely as with shorter-acting alternatives.
Daily Dosing for ED
The 2.5 mg and 5 mg tablets are intended for daily use. You take one at roughly the same time each day, regardless of when sexual activity might happen. The starting dose is 2.5 mg, and it can be bumped to 5 mg if needed. Because the drug stays active so long, taking it daily builds a steady baseline level in your body. The result is that you don’t have to plan doses around sex at all.
Daily dosing tends to appeal to people who prefer spontaneity or who have sex frequently enough that as-needed dosing would mean taking the higher-strength tablet several times a week anyway.
Dosing for an Enlarged Prostate
Cialis is also approved to treat the urinary symptoms of benign prostatic hyperplasia (BPH), the non-cancerous prostate enlargement that’s common in older men. The recommended dose for BPH is 5 mg once daily. If you have both ED and BPH, the dose is the same: 5 mg daily, taken at about the same time each day without regard to sexual activity.
How Other Medications Affect Your Dose
Certain drugs slow down the way your body breaks down tadalafil, which effectively increases how much of the medication stays in your system. Potent inhibitors of the liver enzyme responsible for processing tadalafil, including antifungals like ketoconazole and itraconazole as well as the HIV medication ritonavir, require significant dose adjustments.
If you take any of these medications and use Cialis as needed, the maximum dose drops to 10 mg, and you can’t take another dose for at least 72 hours. If you’re on daily Cialis, the ceiling falls to 2.5 mg. These aren’t optional precautions. Without the adjustment, tadalafil accumulates to levels that raise the risk of side effects like headaches, flushing, low blood pressure, and prolonged erection.
Adjustments for Kidney Problems
Kidney function also changes the equation. If your kidneys are significantly impaired (a creatinine clearance below 30 mL/min) or you’re on dialysis, the as-needed dose should not exceed 5 mg, and it shouldn’t be taken more than once every 72 hours. Daily dosing isn’t recommended at all for people in that category. For moderate kidney impairment, your prescriber will typically start at the lower end of the dose range and adjust from there.
Which Strength Is Right for You
The four strengths map neatly onto two approaches. If you want the flexibility of taking a pill only when you need it, you’ll likely start at 10 mg and move up or down. If you prefer a daily routine that keeps the drug active around the clock, you’ll start at 2.5 mg with the option to go to 5 mg. Your overall health, other medications, and kidney and liver function all influence which dose is appropriate.
Generic tadalafil is available in all four strengths and is chemically identical to brand-name Cialis. The cost difference is substantial, so if price is a factor, generic versions offer the same dosing options at a fraction of the brand-name price.