Prescription only
Tadalafil
Sold as Cialis.
What the label states
The recommended starting dose of CIALIS for use as needed in most patients is 10 mg, taken prior to anticipated sexual activity. The dose may be increased to 20 mg or decreased to 5 mg, based on individual efficacy and tolerability. The maximum recommended dosing frequency is once per day in most patients. The recommended starting dose of CIALIS for once daily use is 2.5 mg, taken at approximately the same time every day, without regard to timing of sexual activity. The CIALIS dose for once daily use may be increased to 5 mg, based on individual efficacy and tolerability.
Quoted from the approved product label. Clinics commonly prescribe differently — more frequent, smaller injections of the same weekly total are routine — and where this site describes that, it is named as practice rather than as labelling.
- Route
- Oral, either as needed before sexual activity or once daily at the same time each day
- Vehicle
- None — a film-coated tablet swallowed whole. There is nothing to reconstitute, dilute or draw up.
- Usual barrel
- None — this compound is not drawn into a syringe
- Strengths covered
- No strength page yet
Why there is no syringe
There is no syringe. Tadalafil is an oral film-coated tablet in strengths of 5 / 10 / 20 mg, swallowed whole, and the only "dose conversion" it involves is picking the right tablet. Naming a barrel here would invent an instrument the reader does not have. What does need converting on this drug is time, not volume: the label's lead time (median 2 hr to peak) and the window after it are the numbers that decide whether a dose works, and /tools/ed-medication-timing does that arithmetic from these same figures.
Administration
- 1
Rule out nitrates before anything else
This is the step that kills people when it is skipped. “Administration of CIALIS to patients who are using any form of organic nitrate, either regularly and/or intermittently, is contraindicated.” (section 4.1 Nitrates). That covers nitroglycerin tablets, sprays, ointments, pastes and patches, isosorbide mononitrate and dinitrate, and the recreational nitrites sold as “poppers”. Guanylate cyclase stimulators such as riociguat are contraindicated too: “Do not use CIALIS in patients who are using a GC stimulator, such as riociguat. PDE5 inhibitors, including CIALIS, may potentiate the hypotensive effects of GC stimulators.” (section 4.3 Concomitant Guanylate Cyclase (GC) Stimulators).
- 2
Check the interval before any nitrate is given
At least 48 hours. “In a patient who has taken CIALIS, where nitrate administration is deemed medically necessary in a life-threatening situation, at least 48 hours should elapse after the last dose of CIALIS before nitrate administration is considered.” (section 7.1 Potential for Pharmacodynamic Interactions with CIALIS). Two of the four labels name an interval that must elapse before a nitrate can even be considered in a life-threatening situation: 12 hours for avanafil, 48 hours for tadalafil. The sildenafil label says it is unknown, and the vardenafil label says it has not been determined. None of the four says a nitrate is ever safe alongside a dose.
- 3
Take it the lead time the label gives
“After single oral-dose administration, the maximum observed plasma concentration (Cmax) of tadalafil is achieved between 30 minutes and 6 hours (median time of 2 hours).” (section 12.3 Pharmacokinetics). Note what that figure is: no lead time on the label — this is Tmax, not onset. No label of the four states an “onset of action”, so nothing on this page presents one.
- 4
Account for food
None. The label states absorption is not influenced by food at all. “The rate and extent of absorption of tadalafil are not influenced by food; thus CIALIS may be taken with or without food.” (section 12.3 Pharmacokinetics).
- 5
Decide which of the two labelled regimens you are on
Tadalafil is the only one of the four with a licensed once-daily regimen, and the two are different drugs in practice. As needed: “The recommended starting dose of CIALIS for use as needed in most patients is 10 mg, taken prior to anticipated sexual activity” (section 2.1). Once daily: “The recommended starting dose of CIALIS for once daily use is 2.5 mg, taken at approximately the same time every day, without regard to timing of sexual activity” (section 2.2). Taking an as-needed dose on top of a daily one is not a labelled regimen.
- 6
Know that the same tablet carries a second indication
CIALIS is also approved for benign prostatic hyperplasia: “The recommended dose of CIALIS for once daily use is 5 mg, taken at approximately the same time every day” (section 2.3). That is a separate indication at the same daily dose, not a bonus effect of the ED dose — and the same section states that “CIALIS is not recommended for use in combination with alpha-blockers for the treatment of BPH.”
- 7
Do not repeat the dose the same day
“The maximum recommended dosing frequency is once per day in most patients.” (section 2.1 CIALIS for Use as Needed for Erectile Dysfunction). The label states an effect lasting up to 36 hours. Thirty-six hours is an efficacy window, not a 36-hour erection — it is how long a single dose still beat placebo.
Storage
- —Store at 25 °C (77 °F); excursions permitted to 15–30 °C (59–86 °F) [see USP Controlled Room Temperature]. Keep out of reach of children — quoted from section 16.2 of the CIALIS label.
- —Keep the tablets in the original container, out of reach of children.
- —Tablets ordered from an unlicensed overseas seller are outside all of this. FDA has repeatedly found products sold as PDE5 inhibitors that contain undeclared active ingredient at undeclared strengths; nothing on this page describes those.
Monitoring
| Marker | When | Why |
|---|---|---|
| Nitrates, nitrites and GC stimulators | Before the first prescription, at every renewal, and before any emergency nitrate | An absolute contraindication, not a caution. “Administration of CIALIS to patients who are using any form of organic nitrate, either regularly and/or intermittently, is contraindicated.” (section 4.1 Nitrates). The same label bars guanylate cyclase stimulators: “Do not use CIALIS in patients who are using a GC stimulator, such as riociguat. PDE5 inhibitors, including CIALIS, may potentiate the hypotensive effects of GC stimulators.” (section 4.3 Concomitant Guanylate Cyclase (GC) Stimulators). |
| Alpha-blocker therapy and blood pressure | Before starting, and again whenever either drug changes | Start at the lowest recommended dose — no figure given. “When CIALIS is coadministered with an alpha-blocker in patients being treated for ED, patients should be stable on alpha-blocker therapy prior to initiating treatment, and CIALIS should be initiated at the lowest recommended dose” (section 2.7 Concomitant Medications). Starting dose on the chart: Lowest dose — not numbered. |
| Fitness for sexual activity | Before starting | The label directs prescribers to consider cardiovascular status before treating erectile dysfunction, because sexual activity itself carries cardiac risk. This is a clinical assessment, not a self-assessment. |
| Sudden vision or hearing loss | Any time during treatment — stop and seek care the same day | The label instructs patients to stop the drug and seek medical attention on sudden loss of vision in one or both eyes, which can signal non-arteritic anterior ischaemic optic neuropathy, and on sudden decrease or loss of hearing. |
| An erection lasting more than four hours | Immediately — emergency care | Priapism can cause irreversible damage to erectile tissue. Every one of the four labels tells patients to seek emergency treatment at four hours, whether the erection is painful or not. |
Frequently asked questions
- What dose does the FDA label actually state?
- The Cialis label's dosage section states: “The recommended starting dose of CIALIS for use as needed in most patients is 10 mg, taken prior to anticipated sexual activity.” It then states: “The dose may be increased to 20 mg or decreased to 5 mg, based on individual efficacy and tolerability.” and “The maximum recommended dosing frequency is once per day in most patients.” The approved as-needed range is therefore 5–20 mg, and the tablet strengths supplied are 5 / 10 / 20 mg. This label lists 5, 10 and 20 mg tablets. The 2.5 mg once-daily starting dose named in section 2.2 is supplied as a generic tadalafil tablet.
- How long before sex should it be taken, and how long does it last?
- The label says to take it median 2 hr to peak, and be clear what that figure is — the basis is no lead time on the label — this is Tmax, not onset. For duration: The label states an effect lasting up to 36 hours. Thirty-six hours is an efficacy window, not a 36-hour erection — it is how long a single dose still beat placebo. “CIALIS for use as needed was shown to improve erectile function compared to placebo up to 36 hours following dosing.” (section 2.1 CIALIS for Use as Needed for Erectile Dysfunction). None of the four labels states an “onset of action”; they state a lead time or a time-to-peak, which are different quantities.
- Can it be taken with nitrates if enough time has passed?
- At least 48 hours. The label's own words: “In a patient who has taken CIALIS, where nitrate administration is deemed medically necessary in a life-threatening situation, at least 48 hours should elapse after the last dose of CIALIS before nitrate administration is considered.” (section 7.1 Potential for Pharmacodynamic Interactions with CIALIS). All four labels contraindicate concomitant use with organic nitrates or nitric oxide donors in any form — nitroglycerin, isosorbide mononitrate or dinitrate, and amyl or butyl nitrite "poppers". A PDE5 inhibitor taken with a nitrate can drop blood pressure to a dangerous level. Guanylate cyclase stimulators such as riociguat are contraindicated on all four labels as well. Where a label declines to name a safe interval, that is not the same as saying none is needed — it is the label saying the answer is not known, and this page does not fill it in.
- What if I am already on an alpha-blocker for my prostate?
- Start at the lowest recommended dose — no figure given. The label states: “When CIALIS is coadministered with an alpha-blocker in patients being treated for ED, patients should be stable on alpha-blocker therapy prior to initiating treatment, and CIALIS should be initiated at the lowest recommended dose” (section 2.7 Concomitant Medications). For benign prostatic hyperplasia the same section goes further: "CIALIS is not recommended for use in combination with alpha-blockers for the treatment of BPH." Both drugs lower blood pressure, so the combination is a dose decision for your prescriber, not an adjustment to make on your own.
- Does tadalafil really work for 36 hours?
- The label states: “CIALIS for use as needed was shown to improve erectile function compared to placebo up to 36 hours following dosing” (section 2.1). Read that precisely. It is an efficacy window — the point at which a single dose still beat placebo in a trial — not a 36-hour erection and not 36 hours of unchanged effect. The 17.5-hour terminal half-life is what produces it, and the same half-life is why this is the only one of the four whose label demands a 48-hour gap before a nitrate can be considered.
- How long after a tadalafil dose can a nitrate be given in an emergency?
- The CIALIS label names a figure, which none of the other three do in the same terms: “In a patient who has taken CIALIS, where nitrate administration is deemed medically necessary in a life-threatening situation, at least 48 hours should elapse after the last dose of CIALIS before nitrate administration is considered.” A second section of the same label words it as “at least 48 hours should have elapsed”. The supporting study found a significant interaction with nitroglycerin at every timepoint up to and including 24 hours, and no detectable interaction after 48. Forty-eight hours is not permission — the label adds that nitrates should then still only be given under close medical supervision.
- Is Cialis the same as Adcirca?
- Same molecule, two separate approvals. CIALIS (NDA 021368) is approved for erectile dysfunction and for benign prostatic hyperplasia; ADCIRCA (NDA 022332) is a 20 mg tadalafil tablet approved for pulmonary arterial hypertension, taken as two 20 mg tablets once daily. They are not substitutes for one another, and a man taking one should not be taking the other.
- Does this page tell me which one to take?
- No. It quotes one label. Choosing between the four is a clinical decision that turns on what else you take — nitrates and guanylate cyclase stimulators rule all four out absolutely — on your cardiovascular status, on whether you want a tablet for an occasion or one every day, and on cost. The side-by-side comparison of all four labels is at /charts/ed-medication-comparison-chart.
Sources
- [1]FDA label — CIALIS (tadalafil) tablet, film coated, Eli Lilly and Company (DailyMed SPL bcd8f8ab-81a2-4891-83db-24a0b0e25895). Dosage, nitrate contraindication, alpha-blocker dosing, pharmacokinetics and storage all quoted from this document. Drugs@FDA: CIALIS is NDA 021368 (Lilly). The 5, 10 and 20 mg tablets are marketed; the 2.5 mg tablet is listed as discontinued, which is why the 2.5 mg once-daily starting dose is dispensed as generic tadalafil.
- [2]Drugs@FDA — ADCIRCA (tadalafil) tablets, NDA 022332, Eli Lilly and Company. The second approved tadalafil product, for pulmonary arterial hypertension, confirming the molecule carries two separate approvals
- [3]Drugs@FDA: FDA-Approved Drugs — the searchable record of every approved application, used to confirm the application number, the approved strengths and the marketing status of each brand named on this page
Related
Educational reference, not medical advice. Dose, route and whether this compound is appropriate at all are decisions for your clinician.