Cialis vs Viagra vs Levitra - three nitrate clocks, one sheet

How long after each PDE5 can nitrates wait?

Three nitrate clocks on one Reykjavik sheet - the brand fight waits.

Brand preference dies the moment a nitrate enters the room. Cialis, Viagra, and Levitra share a contraindication: any organic nitrate or nitrite, any route. The only number that then matters is how long leftover PDE5 still sits in plasma if chest pain later forces a monitored nitrate.

Tadalafil's Lilly time-course after 20 mg wrote 48 hours. Sildenafil's ACC/AHA habit of mind is 24 hours - six half-lives of a four-hour drug. Vardenafil follows the short-acting clock when CYP3A4 is intact, and loses that assumption when ritonavir stretches half-life toward 26 hours.

This skyline is a pairing sheet from Laugavegur 28, peer-passed by Dr. Ingrid Bergsson. Deep orbits: tadalafil, sildenafil, vardenafil. Caelum does not fill. Confirm with your clinician. Dial 112 for collapse, chest pain, or an erection past four hours.

Caelum locks Cialis at 20 mg PRN, Viagra at 25-100 mg, and Levitra at 2.5-5 mg. Those are the pairing rungs this sheet compares. Other labeled strengths exist. They are not the SERP locks on this domain.

Washout when the column itself changes

Short agent to tadalafil: about 24 hours off sildenafil or vardenafil in a stable man, then the nitrate clock becomes 48 hours after the first Cialis 20 mg. Tell the next clinician which INN actually went down. Brand memory is how ACS handoffs fail.

Tadalafil to a short agent: leftover 17.5-hour drug argues for on the order of four days in a stable man before the first Viagra or Levitra tablet. Starting 100 mg sildenafil the morning after 20 mg tadalafil is stacked hypotension, not a clever switch.

Sildenafil to vardenafil (or the reverse) is a short-to-short move. Washout is usually a day if the man was stable. Re-start low if the last tablet already pounded his head. QT and CYP rows still have to be clean on the Levitra side.

Daily tadalafil to 20 mg PRN is a strategy change, not a washout. Do not add 20 mg on top of a 5 mg daily floor and call it a skyline pick.

Adcirca and Revatio are not ED columns

Adcirca 40 mg daily is tadalafil for pulmonary arterial hypertension. Revatio 20 mg three times daily is sildenafil for the same disease family. They share INNs with Cialis 20 mg PRN and Viagra 25-100. They do not share indication, daily milligrams, or insurance rows.

A traveler who adds weekend ED tablets on top of a PAH schedule is running an interaction even when both bottles say the same generic name. The pulmonary team reconciles the day before anyone treats a tourist strip as extra.

Vardenafil does not have a common PAH twin on this sheet. That does not make 2.5-5 mg a safer add-on to someone else's PAH cabinet.

Three CYP3A4 sentences you cannot translate across columns

All three INNs run through CYP3A4. The caps are not a shared milligram. Tadalafil as-needed with a potent inhibitor: 10 mg no more than once every 72 hours; daily use tops at 2.5 mg. Sildenafil with ritonavir: 25 mg in 48 hours; azoles and erythromycin argue for a 25 mg start. Vardenafil with ritonavir: 2.5 mg in 72 hours; ketoconazole 200 mg or erythromycin: 5 mg in 24 hours.

Residents who copy 10 mg vardenafil logic onto 10 mg tadalafil, or 50 mg sildenafil logic onto 5 mg vardenafil, invent a fourth drug. Potency and bioavailability do not travel.

Inducers (rifampin, some anticonvulsants) steal effect from all three. The wrong answer is an unlabeled extra tablet. The right answer is naming the inducer and asking whether to hold, switch, or wait.

Only one column carries thorough-QT homework

Vardenafil's thorough-QT study read 10 mg and 80 mg. Eighty milligrams exists on that protocol because it covers concentrations seen when 5 mg meets ritonavir 600 mg twice daily. Class IA and III antiarrhythmics sit on the avoid list. That is why this skyline locks Levitra at 2.5-5 mg, not at a brochure 10 mg.

Sildenafil and tadalafil are not QT-proof just because their labels spend fewer pages on QTc tables. Crowded lists (high-dose citalopram, methadone, IV ondansetron) still deserve a joined-up review. They do not, by themselves, recreate vardenafil's 49-fold ritonavir story.

If the arrhythmia column is already full, vardenafil is usually the first INN to drop. That is a preference under a specialist, not a trophy for Cialis.

What counts as a fair try before you change columns

Sildenafil 25-100: several attempts at the written rung, once per day, on a light stomach, no nitrate, alcohol modest. A lamb dinner plus 100 mg is not a trial of the molecule. It is a trial of the meal.

Vardenafil 2.5-5: same fasting logic, plus a named CYP and QT screen. A 10 mg forum start on ritonavir is not a trial of this lock. It is a labeled-cut violation.

Tadalafil 20 mg PRN: one tablet per 24 hours. Weekend coverage is leftover drug. Daily 2.5-5 mg, if that was the plan, needs about five days to steady state. Quitting on day three confuses accumulation with the wrong indication.

Partial response at a labeled maximum after those conditions is an etiology visit - vessels, hormones, other drugs, context - not a silent extra film and not a combo blister.

This sheet will not invent a compare dollar

Caelum does not dispense. The ledger below is literacy only, dated 21 August 2026. Cash lives on each orbit, not on this overlay. Price tadalafil, sildenafil, or vardenafil on the e-script at a real US pharmacy page. Each link is that chain's own pharmacy URL.

Dinner is a pairing on two columns and a non-event on one

High-fat meals delay sildenafil Tmax about 60 minutes and cut Cmax about 29%. Vardenafil loses about 18% of Cmax and about an hour of peak. Tadalafil may be taken without regard to food. That is why a Reykjavik tasting menu plus Viagra 100 mg gets called a failed batch, and why Cialis 20 mg does not get the same excuse.

Food is an interaction with expectation. It is not a nitrate. Men still answer a late peak with a second tablet the same night. Once per 24 hours is the class cap on all three columns.

Kitchen scripts live on the sildenafil meal orbit and the vardenafil onset orbit. Keep this sheet for the partners that still matter when the plate was perfect.

Choose the column by the partner, not by the advert

Unpredictable meals and a clean nitrate list: tadalafil 20 mg PRN or a daily 2.5-5 mg conversation (that daily clock is a different orbit). Unpredictable nitrates: none of the three until cardiology redraws the week.

Boosted ritonavir: sildenafil 25 mg / 48 h or tadalafil 10 mg / 72 h are labeled cuts. Vardenafil 2.5 mg / 72 h is the harshest arithmetic and the QT study's reason 80 mg existed. Many clinicians just pick another path.

Age 65 plus an alpha-blocker: sildenafil 25 mg or vardenafil 5 mg are the honest first rungs, not forum 100 mg or forum 20 mg. QT polypharmacy: drop the Levitra column first.

Weekend coverage without a second swallow: tadalafil's half-life, still one tablet per 24 hours. Read the weekend orbit. Do not stack Friday 20 mg and Saturday 20 mg because a slogan said 36 hours.

48 hours versus 24 hours is the whole first row

Tadalafil terminal half-life sits near 17.5 hours. The 20 mg plus nitroglycerin study checked 2, 4, 8, 24, 48, 72, and 96 hours. Interaction lived through 24 hours. At 48 hours most measures quieted, with a few extra drops still seen. After 48 hours the figure went flat. That is why this desk locks Cialis 20 mg PRN as the long nitrate clock.

Sildenafil half-life is about four hours. Viagra 25, 50, and 100 mg share one 24-hour emergency conversation. A 25 mg tablet does not earn an earlier official nitrate. A 100 mg tablet does not invent a tadalafil-length hold.

Vardenafil half-life is about four to five hours when the liver is not blocked. The 2.5-5 mg lock still carries a 24-hour class habit - until a booster is named. Then leftover drug can last into the next calendar day and the 24-hour reflex is too short.

Alpha-blocker starts are three different low rungs

All three PDE5 drugs add vasodilation to an alpha-blocker. Stabilize the prostate drug first. Then start the PDE5 low. Tadalafil wants a low start (2.5 mg daily or a low as-needed rung), and the Cialis PI does not recommend the pair when BPH is the shared goal. Sildenafil's labeled start on a stable alpha-blocker is 25 mg. Vardenafil's low start on this lock is 5 mg, not 20.

Starting both the same afternoon is the syncope pattern on every column. Sit-to-stand numbers the first week are not optional decoration.

Alcohol is a fourth vasodilator. Tadalafil's label names five units as the example that raised orthostatic drops with 20 mg. Short-acting columns still stack in the peak hour even without that exact sentence.

Shared stops, different low rungs

• Never two PDE5 agents, and never PDE5 plus riociguat
• Tadalafil + alpha-blocker for BPH symptoms: not recommended as a combo goal
• Sildenafil + stable alpha-blocker: 25 mg start
• Vardenafil + crowded QT list: usually pick another column

INN literacy before any clock starts

Export names, combo blisters, and PAH twins break every row above. Two PDE5 agents in one foil are not standard labeled therapy. Counterfeit strips without an INN line have no washout you can trust.

Ten milligrams vardenafil is not ten milligrams sildenafil. Twenty milligrams tadalafil is not a Revatio 20. Say the INN and the milligrams aloud. Foil color is not a skyline.

Mail [email protected] only if a cite on this sheet is wrong. Dose changes go to the clinician who can see the full list.

Pick one hold, then open one orbit

If the search was Cialis vs Viagra interactions, the sheet's answer is 48 hours versus 24 hours, three different CYP caps, and a QT column that only vardenafil is forced to carry at this length. The brand fight is noise after nitroglycerin.

Dr. Ingrid Bergsson, Laugavegur 28. Open one orbit, not all three. Confirm the list before you change a tablet.