Three clocks: 10 mg tadalafil, 100 mg sildenafil, 10 mg vardenafil

Three labelled clocks, not one winner

Three oral PDE5 inhibitors share one enzyme. They do not share a useful clock. That is the comparison I file in Lyon. Brand names sit on the boxes. The clocks sit in the pharmacokinetics.

Tadalafil, sildenafil and vardenafil all leave more cGMP in penile smooth muscle once nitric oxide has already started the chain. None of them starts desire. Swallow any of them in a quiet room and you get vessel effects, not an erection. The advertisement that skips that sentence is selling a switch the label never wrote.

I lock three strengths because those are the ones this cabinet keeps in view. Tadalafil 10 mg is the labelled as-needed start. Sildenafil 100 mg is the labelled ceiling for most men after 50 mg has been tried or set aside. Vardenafil 10 mg is the labelled start once the QT question is answered. Milligrams are not interchangeable across the three boxes.

Onset looks similar if you only read the first half hour. Duration does not. Food moves sildenafil hard and vardenafil a little. Tadalafil ignores the plate. Vardenafil carries a measured QT change the other two do not put on the same warning line. Those four facts decide more prescriptions than potency slogans.

What follows is the open-dose-mail-file order I actually use. Open the labels. Lock the dose. Answer the specific mail. File the note. If a first evening fails, I look at food, arousal and timing before I change the molecule.

The 100 mg sildenafil meal

Pfizer's Viagra label starts most men at 50 mg, about an hour before sex. The allowed window is 30 minutes to 4 hours. The labelled maximum is 100 mg. That 100 mg tablet is the lock this site keeps in the title, because it is the ceiling many first-timers are already holding, not because bigger is kinder.

A high-fat meal delays Tmax by a mean of 60 minutes and cuts Cmax by 29%. Total exposure stays similar. The evening just arrives late and flatter. That single meal fact explains more 'it did nothing' letters than a weak batch ever will.

RigiScan work in the label shows an effect for up to 4 hours, weaker at 4 hours than at 2. Terminal half-life is about 4 hours for parent and metabolite. After a 100 mg dose in healthy men, plasma at 24 hours is about 2 ng/mL against a peak near 440 ng/mL. The leftover is small. The nitrate question is not closed. The label still says it is unknown when nitrates can be given safely after sildenafil.

One dose per day is the frequency cap. A second 100 mg tablet the same night is not a rescue. It is an extra vasodilator load. Age over 65, cirrhosis, or creatinine clearance under 30 mL/min all push levels up. Ritonavir raised sildenafil AUC about 11-fold. The labelled cap there is 25 mg in 48 hours.

The first-night walk-through is the 100 mg first-timer note. If dinner was heavy, judge the tablet later, or wait for a lighter plate before you call 100 mg a failure.

The 10 mg tadalafil span

Lilly's Cialis label starts most men at 10 mg as needed, taken before anticipated sex. The same page allows a rise to 20 mg or a drop to 5 mg. Once a day is the ceiling. A second tablet the next morning is a stacked dose.

The 36-hour line is a trial result, not folklore. In the labelled 36-hour study, successful intercourse after 10 mg was 56% of attempts versus 33% on placebo. At 24 hours the same 10 mg arm was 56% versus 42% on placebo. Those are mean per-patient rates, not a promise that every Saturday night is covered.

Mean terminal half-life is 17.5 hours. Median time to peak is 2 hours, with a range from 30 minutes to 6 hours. Food does not change that absorption. That is why a 10 mg tablet on Friday evening can still be useful on Saturday without a second swallow.

Daily tadalafil is a different prescription. The labelled daily start for ED is 2.5 mg, with a possible rise to 5 mg, taken at about the same time each day. I do not treat 10 mg as-needed and 2.5 mg daily as the same habit with a bigger pill. They answer different weeks.

The long clock has a long risk tail. If nitrates become medically necessary after tadalafil, the US label wants at least 48 hours after the last dose before nitrates are even considered, and then only under close monitoring. Back ache, when it comes, often arrives 12 to 24 hours after the dose and usually settles within 48 hours. You wait that out. You do not add a second PDE5.

The nitrate ban they share

Organic nitrates are contraindicated with all three. That sentence is not a preference. Glyceryl trinitrate spray, isosorbide tablets, and recreational nitrites (poppers) all donate nitric oxide. PDE5 blockade keeps cGMP up. Together they can drop blood pressure into a range that is dangerous in a chair, and worse on a stairs.

Regular nitrate use and intermittent nitrate use are both bans. There is no safe gap I can write for a man who keeps a spray in his pocket and wants a weekend tablet 'just in case'. Tadalafil makes that pocket problem longer because of the 17.5-hour half-life. Sildenafil's leftover at 24 hours looks tiny on paper. The Viagra label still will not name a safe hour for nitrates after a dose.

Riociguat, a guanylate cyclase stimulator, is also banned with sildenafil. I treat that as the same family of stacking on the nitric oxide path. Alpha-blockers are not an automatic ban. They need a stable dose first, then a low PDE5 start, because both families lower pressure. That is a caution, not the nitrate sentence.

If chest pain starts after any of these tablets, say the name of the tablet before anyone reaches for nitrate. Emergency teams can work without that spray. They cannot safely guess whether a PDE5 is still on board. With tadalafil the labelled emergency hold is at least 48 hours after the last dose before nitrates are considered, and only with monitoring.

I will not soften this for a man who 'only uses the spray twice a year'. Twice a year is enough. See the cardiologist first. Leave the PDE5 shelf closed until the nitrate is off the list.

Matching a life to a clock

I do not rank a winner. I match a week. A couple that hates an appointment on the calendar often does better with daily 2.5 or 5 mg tadalafil than with any as-needed tablet, including 10 mg tadalafil. That is a daily prescription. It is not a 10 mg tablet taken 'most days'.

A man whose sex life is occasional, and who can see Friday coming, is the classic 10 mg tadalafil as-needed file. He swallows once. He does not need a second clock on Saturday. If his evenings are one-off and he wants the drug gone by morning, 100 mg sildenafil or 10 mg vardenafil fit better, food and QT permitting.

Heavy dinners that will not move point away from sildenafil as the first lock. Tadalafil ignores the plate. Vardenafil notices a very fatty meal and then recovers. If the man already takes quinidine, procainamide, amiodarone or sotalol, vardenafil is off the first page no matter how tidy the 10 mg start looks.

Diabetes does not pick a winner by itself. Some clinics reach for vardenafil when sildenafil felt patchy, but that is practice, not a labelled superiority claim. I still fix the plate and the arousal before I switch the molecule. A nervous first night on 100 mg sildenafil after steak is not a vardenafil indication.

Cost used to sort the three. Generics flattened that. What still sorts them is time, food, QT and the nitrate pocket. Those four stay after the price argument dies.

The 10 mg vardenafil QT line

Levitra's US start for most men is 10 mg, taken about 60 minutes before sex, once a day. The dose may rise to 20 mg or fall to 5 mg. Sexual stimulation is still required. I do not write that 10 mg until I have asked about the QT line.

A dedicated QT study in middle-aged men found a mean QTcF increase of 8 msec after 10 mg versus placebo. An 80 mg dose, four times the labelled maximum, gave about 10 msec. Moxifloxacin 400 mg, the positive control, sat in the same small band. The clinical meaning of that 8 msec shift is unknown in a mixed clinic list. The label still draws a hard avoid line.

Men with congenital long QT should not start vardenafil. Class IA drugs such as quinidine and procainamide stay off the combination. Class III drugs such as amiodarone and sotalol stay off as well. If those names are already on the list, I file sildenafil or tadalafil instead, or I leave the class alone.

Food is allowed. A high-fat meal still slows the peak. European product information puts the delay at about 1 hour and the Cmax cut at about 20% after a 57% fat meal. A ordinary dinner is usually quieter than that. I still prefer a lighter plate on a first 10 mg night so we are not arguing with both QT caution and delayed absorption.

The dedicated vardenafil note on this cabinet is the 10 mg QT-first note. The comparison point is simple. Vardenafil is the short clock with an extra electrical gate. It is not a secret stronger Viagra. It is a different start rule.

One tablet, then a switch if needed

Each label caps frequency at once per day for the as-needed strengths we lock here. Daily tadalafil is the exception, and it uses 2.5 or 5 mg, not 10 mg. Crossing from 10 mg tadalafil on Friday to 100 mg sildenafil on Saturday is two PDE5 loads inside one long tadalafil tail. I do not do that.

If 10 mg tadalafil is weak after a few aroused attempts, the labelled move is 20 mg, or a drop to 5 mg if the back ache is the problem. If 100 mg sildenafil is already the tablet in the bottle and the night was quiet, I do not add vardenafil at 1 a.m. I look at the meal and try another evening.

Switching molecules waits until the first clock has cleared. Sildenafil and vardenafil are short. A night off is usually enough. Tadalafil is not short. Give it the weekend it already bought before you start a new name.

CYP3A4 inhibitors change all three. Ketoconazole, itraconazole, clarithromycin, erythromycin and ritonavir are the names I ask for by list, not by memory. Dose caps differ. Ritonavir plus sildenafil is a 25 mg story. Ritonavir plus vardenafil is a 2.5 mg in 72 hours story. I do not improvise those numbers.

A pharmacy with a named prescription is part of the clock. Counterfeit ED tablets are common. A mystery 100 mg score from a banner ad is not a sildenafil evening I can file. Bring the box you actually swallowed if you write to the mailbag about a failed night.

Headache is common. The tilt is not

Headache, flushing, a blocked nose and indigestion sit on all three lists. They come from the same vessel relaxation that the erection uses. They are common. They are usually short. They are not a reason to double the next tablet.

Sildenafil is the one most often blamed for a blue tinge or extra light sensitivity. That tracks PDE6 activity in the retina. It usually fades as the 4-hour clock runs down. Sudden loss of vision is a different sentence. Stop. Get seen. Do not wait to see if the tint 'settles into blindness'. It should not.

Tadalafil's extra mark is back and thigh ache. The US label places most of that 12 to 24 hours after the dose, with resolution inside 48 hours for most men. About 0.5% stopped as-needed tadalafil because of it. Acetaminophen or an NSAID is what the trials used when treatment was needed. A second PDE5 the same weekend is not treatment.

Vardenafil's everyday list looks like sildenafil's. The extra page is the QT line, not a unique headache. Dizziness on standing can still happen because pressure is a little lower. Stand slowly. Drink water. Do not stack alcohol on a first night and then blame the 10 mg tablet.

Two emergencies are class-wide. An erection past 4 hours needs urgent care. Tissue injury is the risk, not embarrassment. Sudden hearing loss is the other stop rule. Those two lines go on every page I write, whatever clock we picked.

When the clock is the wrong tool

Low desire is not a PDE5 problem. If the mail says the erection is fine when the mood is there, and the mood is rarely there, I do not pick among 10 mg, 100 mg and 10 mg. I ask about sleep, alcohol, antidepressants, prolactin and testosterone the way any GP should. A tablet that waits for nitric oxide cannot invent the first signal.

Painful intercourse, a bend that is new, or a penis that stays partly filled for hours are also the wrong file for a comparison table. Those need a person in a room, not a clock metaphor. Peyronie's, priapism risk and pelvic pain get referred, not titrated.

The three clocks still earn their page when the plumbing is the complaint and the nitrate shelf is empty. Read the tadalafil remedy if the 36-hour span is the draw. Read the sildenafil remedy if the evening is short and the plate can be light. Read the vardenafil remedy only after the QT line is clear.

I am Rosalind Hartley. This journal is education from a Lyon GP, not a shop and not a prescription. Your own clinician still has to see your list before any of these clocks is started. If the mail is about desire, sleep or a new bend, send that plainly. I will not answer it with a comparison table.