Selectivity is the first stamp, not a slogan
A selectivity-and-QT file. Not a second vardenafil monograph. Five or ten after the rhythm drugs are off the tray.
In-vitro ink on the Levitra label is specific: more selective for PDE5 than for the other known phosphodiesterases, greater than 15-fold versus PDE6, greater than 130-fold versus PDE1, greater than 300-fold versus PDE11, and greater than 1,000-fold versus PDE2, 3, 4, 7, 8, 9, and 10. Those ratios are why this study exists. They are not a trophy speech.
Fifteen-fold over PDE6 is a neighbour, not a locked door. Photoreceptors still sit close enough that a colour haze can appear, usually less loudly than with sildenafil, still real. Three-hundred-fold over PDE11 is why back-ache is not this molecule's signature the way it is on the tadalafil card.
Knock nitrates and nitric-oxide donors first anyway. The label does not even grant a defined safe interval after a vardenafil swallow. That silence is stricter than tadalafil's 48-hour line. Selectivity does not reopen a shut drawer.
Why 5 mg and 10 mg both exist
Most adults open at 10 mg, about 60 minutes before activity, once per day maximum. The dose may fall to 5 mg or, after a real reason, rise toward 20 mg. This floor locks the conversation at 5 or 10. That is the SERP room and the ward habit: prove the mid card before anyone talks about a top count.
Five milligrams is not a timid extra. Age 65 and over: consider 5 mg first, because elderly men showed about 34 percent higher Cmax and 52 percent higher AUC than younger men. Moderate hepatic impairment (Child-Pugh B): start 5 mg, and do not exceed 10 mg. Stable alpha-blocker therapy: 5 mg is the labeled greeting.
Potent CYP3A4 inhibitors cut harder. Ritonavir: no more than 2.5 mg in a 72-hour span. High-dose ketoconazole or itraconazole and several protease inhibitors: 2.5 mg in 24 hours on older ink. Those cuts are why a 10 mg habit can be wrong even when the man is not elderly.
Moderate inhibitors such as erythromycin or 200 mg ketoconazole historically capped the film tablet at 5 mg in 24 hours. I still want the live label in the room, because antiviral lists move. The habit is: chart the 3A4 drug before you defend a 10 mg greeting as 'usual.'
The QT line before anyone reaches for 20
A thorough QT study put 10 mg and a supra-therapeutic 80 mg against placebo and moxifloxacin. Mean QTc stretch was about 8 msec at 10 mg and about 10 msec at 80 mg. Small in a healthy volunteer. Not small if the interval is already long or if another QT drug is on the list.
Avoid congenital long-QT. Avoid Class IA antiarrhythmics - quinidine, procainamide. Avoid Class III - amiodarone, sotalol. Low potassium or magnesium makes the same line sloppier. This is why 20 mg is not a prize we reach for to prove the card is strong.
Gatifloxacin plus vardenafil added a further stretch in a dedicated pairing. The lesson is additive, not exotic. Chart the rhythm list before you praise a mid-card onset.
Moxifloxacin sat in that thorough-QT study as the positive control, which is how you know the assay could see a stretch. An 8 msec mean at 10 mg is easy to shrug at in a healthy volunteer. It is not a shrug if the baseline QTc is already 470 msec or the list already holds sotalol.
Class IA and III stay off this tray
Holds that beat a 5-or-10 preference
- Congenital long-QT - tray empty
- Class IA: quinidine, procainamide - tray empty
- Class III: amiodarone, sotalol - tray empty
- Nitrates or riociguat - tray empty, no home interval
Quinidine and procainamide sit on the IA shelf. Amiodarone and sotalol sit on the III shelf. Any of them plus vardenafil is a pairing I will not walk into for a quality-of-life tablet. Ask the question before the milligram.
Other QT-stretching drugs and a low potassium make a softer, still-real caution. The consult is a full list, not a yes on Levitra because PDE5 ratios look pretty.
Nitrates remain an absolute. The label never defined a safe later interval. Riociguat is the same stacked-cGMP stop as the rest of the class. Selectivity ratios do not bargain those two.
Timing the hour, not winning a race
Film-coated Levitra may be taken with or without food. Median Tmax is about 60 minutes fasting, range roughly 30 minutes to 2 hours. A very fatty plate can still blunt and delay the peak. The hour on the label is a teaching clock, not a stopwatch prize.
Stimulation is still required. A selective enzyme hold does not invent desire. Men who swallow 10 mg and wait in a quiet room for a spontaneous event are testing the wrong hypothesis.
Common vasodilator effects - headache, flush, stuffy nose, dyspepsia - come from the intended job spilling into other beds. They are dose-linked. They are not proof the QT line was ignored. Keep the two stories in different rooms.
Approval in 2003 put this card on US shelves five years after the diamond. It was never a replacement trophy. It was a second short-acting tool with a tighter PDE5 fit and a louder electrical footnote. That is the whole reason 5 or 10, after the QT line, is how this floor speaks.
Twenty waits until the ward has a reason
Twenty milligrams exists on the bottle. It does not exist as this site's greeting. Rise only after 10 mg has been tried, flush and headache are known, and the QT list is clean. Using 20 mg to win a comparison with a friend's tadalafil 20 is a category error. Different clocks. Different locks.
Half-life of parent and M1 metabolite is about 4 to 5 hours. Clearance about 56 L/h. Most of the metabolites leave in faeces (about 91 to 95 percent). This is a short card, like sildenafil, not a 36-hour window. If he wants a weekend tail, he is asking for a different molecule - see the daily-versus-once file.
Staxyn, the orodispersible 10 mg, is not a silent swap for film-coated 10 mg. Exposure is higher. Treat them as related products, not identical chips. This study stays with the film-coated 5-or-10 lock.
Severe hepatic disease (Child-Pugh C) is generally a stay-away on the film tablet. Dialysis data are thin. I do not invent a 5 mg courtesy start in those rooms to be kind. Kindness is sending the man back to the clinician who owns the liver or the dialysis shift.
PDE6 sits closer than marketing admits
In-vitro selectivity from the US vardenafil label. Ratios are not a clinical trophy.
| Isoenzyme | Levitra label ratio vs PDE5 | Ward reading |
|---|---|---|
| PDE6 | >15-fold | Nearest cousin; possible colour haze |
| PDE1 | >130-fold | Vessel/pressure rooms stay mostly aside |
| PDE11 | >300-fold | Back-ache less typical than tadalafil |
| PDE2/3/4/7-10 | >1,000-fold | Far cousins on this ink |
PDE6 lives in the retina. A drug shaped for PDE5 will always be judged by how sloppy that fit becomes at the cousin. Greater than 15-fold sounds impressive in a slide deck. On a ward it means some men still notice brightness or a blue-green shift, especially as the milligram climbs.
Do not confuse that haze with sudden vision loss. The haze is off-target pharmacology. Sudden loss is a rare, separate emergency. Mixing the two sentences is how men either panic at a tint or ignore a true stop signal.
NAION reports sit on the whole class after marketing, not on a Levitra-only footnote. I mention them here so selectivity does not get sold as eye insurance. A man with a crowded disc or prior NAION needs an eye opinion, not a ratio.
If visual nuisance is the complaint that brought him off sildenafil, vardenafil may or may not be quieter. Tadalafil is the cousin with almost no PDE6 story. That is a matching fact, not a ranking. See the origin card for why the haze was already in the 1991 volunteer notes.
Sign-out: a mid card, not a trophy
Sign-out vardenafil as a mid card. Stamp selectivity. Stamp the QT line. Offer 10 mg to a typical adult, 5 mg to the slower-clearing or alpha-blocked man, and leave 20 on the shelf until a ward has a reason. Nitrates still empty the tray.
If the complaint is colour haze, back-ache, or a 36-hour window, you may be matching a different card, not losing a trophy. Take that match to a clinician. This floor does not hand out bottles.