Why did Cialis show up years after Viagra if the idea was the same enzyme?
Five years late is not the same as five years lost
Pfizer launched sildenafil in 1998 and owned the conversation.
Cialis 10 to 20 mg PRN did not get a US stamp until 21 November 2003.
By 2003 the class already had a public face, a nitrate scare, and a set of jokes. Pfizer had spent five years teaching men, partners, and emergency rooms that an oral PDE5 tablet existed. Arriving second is usually a burial. Here it was a briefing.
A second-wave tablet has to answer a rude question: why switch if the first one already works? ICOS could not win on novelty of the enzyme. Both drugs block PDE5. The only honest wedge was time in the body. Mean terminal half-life about 17.5 hours in healthy men - roughly four times the sildenafil clock - and a labeled window of responsiveness out to 36 hours after a 10 or 20 mg PRN dose.
I still write that gap in the margin as a feature, not a wound. The market was already educated. Couples already knew the spray was a hard stop. What they did not have was a Friday tablet that still answered on Sunday without a second swallow. That is the only reason a late almond survived a first-mover brand.
Peer line from the Aberdeen desk: do not romanticize the delay. Five years also meant five years of nitrate stories, blue-vision jokes, and food rules that tadalafil would later dodge. The class arrived pre-scared. Cialis inherited the scare and added a longer wait.
The labeled start for most men was, and still is, 10 mg taken before anticipated sex, with room to 20 mg or down to 5 mg. That ladder is the commercial object this page is about. Daily 2.5 and 5 mg came later. BPH at 5 mg later still. The 2003 bottle was a PRN almond.
Bothell wrote IC351 before Indianapolis had a brand
Bothell sat north of Seattle and did not look like a men's-health house. ICOS opened in 1989 around cell-signalling and inflammation, the usual biotech bet. PDE5 was not the founding sermon. IC351 showed up in the mid-1990s as a structurally different inhibitor - not a sildenafil cousin with a new paint job - and the early PK panels already whispered an awkward half-life.
Glaxo had a 50/50 discovery pact with ICOS from 1991. When the compounds failed to sit in Glaxo's core markets, the pact lapsed in 1996. That walk is the first margin I circle. A long half-life is only an asset if someone will pay for Phase III. A lapsed pact is how a molecule almost dies in a notebook.
ICOS was not testing IC351 as an erection drug on day one. Pfizer's sildenafil heart program leaked the PDE5-erection link in 1994. ICOS already held a patent on IC351 that year and started Phase 1 in 1995. Phase 2 for men with ED opened in 1997. The science was ready before the sales story existed.
I keep a blunt note next to the ICOS name: nobody in a waiting room had heard of them. That is not an insult. It is why Lilly's letterhead mattered. Discovery credit and a global label are different jobs. The tadalafil medicine page keeps the labeled milligrams. This page keeps the shop that found them.
Structurally, tadalafil is not a sildenafil lookalike. That matters for PDE6. Sildenafil nicks the retinal enzyme enough to explain the blue-tint stories. Tadalafil is far more selective for PDE5 over PDE6. The vision complaint almost vanishes from the tadalafil rows. A different scaffold is not trivia. It is why the side-effect page does not read like a Viagra photocopy.
Lilly wrote the cheque the year Viagra taught the market
Lilly ICOS LLC formed in 1998 as a 50/50 joint venture.
ICOS brought the molecule. Lilly brought Phase III money and a regulatory machine.
The calendar year is the tell. Viagra launched, and a late PDE5 program could finally raise a serious budget because the market size was no longer a guess. ICOS could not have funded a global ED program on a Bothell burn rate. Lilly would not have written the cheque without a PK hook that was not a photocopy.
The split was classic biotech-pharma. ICOS kept discovery credit and a share of upside. Lilly carried trial cost, label language, and the sales force that would have to say '36 hours' without promising a two-day erection. Anyone who has sat in a urology corridor knows how fast that sentence gets misunderstood.
Two years later the venture filed the NDA under the generic tadalafil and the brand Cialis. May 2002, Orlando AUA: Brock's integrated efficacy pack and Porst's 36-hour timing data went public. Europe stamped the drug in late 2002. The FDA waited until 21 November 2003. Same molecule, staggered desks.
Lilly bought ICOS outright in 2007 and closed the biotech chapter. Partner first, owner later. I write that as a calendar, not a morality play. The almond on the bottle did not change shape when the letterhead did.
If you want the trial numbers that made the cheque look sane, leave this history blotter and open the Cialis 20 mg trial-row note. History is the shop and the date. Evidence is the IIEF and the spray.
Seventeen and a half hours became the product
Mean terminal half-life sits at about 17.5 hours in healthy men and closer to 21.6 hours in older men. Sildenafil and vardenafil live nearer four. That is the entire commercial difference in one number. Everything else - weekend talk, daily lanes, a BPH stamp - is a downstream use of the same clock.
A half-life is not a promise of a continuous erection. I have to write that in the margin every time a magazine repeats '36 hours.' The labeled claim is improved erectile function compared with placebo up to 36 hours after a PRN dose, with arousal still required. No stimulation, no event. The tablet buys a window. It does not book the appointment.
Couples who hated the stopwatch already knew the cost of a short tablet. You swallow, you wait, you hope the evening matches the Tmax. Tadalafil's mean Tmax is about two hours - slower than sildenafil - so the honest counsel is not 'faster.' It is 'wider.' Friday night still covers Sunday morning for a lot of men on 10 or 20 mg PRN. That is the human fact the ads flattened into a slogan.
Food does not blunt tadalafil the way a greasy plate blunts sildenafil. The label says take it without regard to meals. I still ask what people ate, because habits lie, but the PK row is clean. The 10 mg PRN versus daily-almond ledger is where that food-neutral clock turns into a schedule choice.
Peer line: memorize 17.5 hours for the exam, then immediately write 36 hours and 48 hours next to it. Those three clocks do different jobs. Half-life is PK. Thirty-six is the efficacy window. Forty-eight is the nitrate hold. Mixing them is how residents get the spray wrong.
The 2003 bottle started at 10 mg, not at a slogan
FDA start for most men: 10 mg before anticipated sex.
Step to 20 mg or down to 5 mg on effect and tolerability.
The FDA starting dose was 10 mg taken prior to anticipated sexual activity. The 2003 letter also allowed 20 mg if 10 mg was not enough, and 5 mg if other drugs or organs asked for a smaller swallow. Once per day was the ceiling in most men. That is the PRN ladder this site locks in the SERP: 10 to 20 mg as needed.
Almond-shaped, film-coated, yellow, debossed C 10 or C 20. I mention the shape because later daily tablets reused the same silhouette at 2.5 and 5 mg, and men mix bottles. Shape is not a dose. Read the stamp.
CYP3A4 sits under the dose. Ketoconazole or ritonavir: PRN ceiling 10 mg, and not more often than every 72 hours. Moderate or severe kidney impairment starts lower and stretches the interval. Mild or moderate liver impairment caps PRN at 10 mg. None of that was marketing. It was the first label's fine print, and it is still the fine print.
Back pain and myalgia showed up more often on tadalafil than the class jokes had prepared people for. In the pharmacology panels the ache often started 12 to 24 hours after a dose and faded inside 48 hours - a delayed, bilateral, recumbency-worsened complaint, not a disc story. About half a percent of on-demand users stopped for it. I still warn for it, because a Sunday ache after a Friday 20 mg is how men decide the drug 'did something wrong' when the clock did exactly what the PK said.
The 2003 FDA note also said the drug stays in the body longer than the two tablets already on the shelf. That sentence is the whole approval rationale. Not prettier. Longer. The DailyMed Cialis label still opens the PRN section on 10 mg.
The half-life then rented three more labels
1989
ICOS opens in Bothell around cell signalling, not men's health.
1994-1995
IC351 is patented; Phase 1 starts. Pfizer has already seen the PDE5-erection leak.
1996
The Glaxo-ICOS pact lapses. The molecule still needs a payer.
1998
Lilly ICOS forms. Viagra launches the same year and proves the market.
2002-2003
AUA timing data; EU stamp late 2002; FDA Cialis stamp 21 November 2003 for PRN ED.
2007-2011
Lilly buys ICOS. Daily ED 2008. Adcirca 2009. BPH 5 mg 2011.
Daily 2.5 mg arrived in 2008 as a once-daily ED lane, with a step to 5 mg. Steady state in about five days. That schedule only makes sense because the half-life is long enough to hold a trough. Short PDE5 tablets never earned a serious daily ED stamp.
Adcirca, 2009: tadalafil 40 mg once daily for pulmonary arterial hypertension, a different brand, a different clinic, a walk-distance endpoint. Same enzyme, different bed. I write a hard peer line here. Do not count Cialis almonds into an Adcirca day. Do not cut a 40 mg PAH tablet into ED pieces. The molecule is shared. The label is not.
BPH at 5 mg once daily landed in 2011, with a combined ED-plus-BPH stamp on the same 5 mg clock. Older men already carried both complaints. One evening swallow that moved IPSS a little and kept the erection lane open was a urology convenience, not a prostate shrinker. Flow-dominant obstruction still needs a different plan.
I use a timeline when a story is really a calendar. The dates below are the ones I keep in the blotter. They are not a novel.
What a late 10-to-20 mg almond actually taught the desk
A second-wave PDE5 inhibitor can win if the patient feels a real clock change. Copycat branding cannot. That is the only moral I will allow this history. ICOS found a long half-life. Lilly paid to prove men noticed. The weekend slogan was downstream advertising, not the discovery.
The hold did not get kinder because the tablet lasted longer. Nitrates stayed contraindicated. The wait after the last Cialis swallow stretched to 48 hours, with monitoring if a life-threatening angina forced the issue after that. Duration is a feature in the bedroom and a liability in the crash cart. Both sentences belong in the same margin.
If you came here for a shopping list, you are in the wrong building. This desk does not fill. The tadalafil medicine note is the labeled map. The PRN versus daily ledger is the schedule argument. This page is only why a 10 to 20 mg almond was allowed to arrive late and still stay.
Bring the spray list to your own clinician before anyone writes a first 10 mg. A history blotter is not a standing order.
Reader mail
Reader questions on this article
Answered by Dr. Julian Frost, MD · Urology & men's sexual health
History-desk mail. I answer the shop, the date, and the clock - not your refill.
Same enzyme, different clock. ICOS had IC351 in the mid-1990s, but Glaxo walked in 1996 and Lilly did not form the venture until 1998 - the year Viagra proved men would pay for an oral PDE5 tablet. Phase III, a brand, and a US stamp take years even when the molecule is already named. The FDA date is 21 November 2003. The scientific idea was not five years late. The bottle was. That delay is why the only honest pitch left was duration: 17.5-hour half-life, 10 to 20 mg PRN, a 36-hour window. A me-too short tablet would have died in that gap.
Was ICOS a real company or a footnote Lilly invented later?
Real shop. Bothell, 1989, cell-signalling work, not a men's-health storefront. IC351 was their number. Phase 1 in 1995, Phase 2 for ED in 1997, Lilly ICOS in 1998, Lilly buyout in 2007. I keep ICOS in the margin because discovery credit and a global sales force are different jobs. Patients never needed the letterhead. Prescribers did, because someone had to fund the 1112-man integrated pack and the nitrate pharmacology. A footnote does not run Phase III.
If it lasts into a second day, is that automatically more dangerous than Viagra?
Not more poisonous by milligram. More persistent. Headache, flush, dyspepsia, a delayed back ache - those can linger because the drug lingers. The danger that actually changes practice is the nitrate clock. After tadalafil the labeled wait before a nitrate, if a life-threatening angina forces the issue, is at least 48 hours, and even then only under monitoring. Sildenafil's traditional teaching was closer to 24 hours. Longer in the bedroom means longer on the crash-cart list. That is the trade, not a toxicity contest.
What does weekend pill actually mean in a clinic, not in an ad?
It means a Friday 10 or 20 mg PRN swallow can still support a Sunday attempt for many men, provided there is arousal and no second tablet that day. It does not mean a 36-hour erection. It does not mean you skip the spray question. I almost never use the slogan with a first-time patient because it teaches the wrong picture. I say: wide window, still need stimulation, still once daily at most, still a 48-hour nitrate hold. If the slogan helps a couple stop watching the clock, fine. If it makes them reckless with a GTN spray, it has failed.
How can the same molecule treat lungs and erections? That sounds like a trick.
PDE5 lives in more than one vascular bed. Block it in cavernosal muscle and an erection can fill when nitric oxide shows up. Block it in pulmonary arterioles and the right heart may see a lower load. Adcirca is tadalafil 40 mg daily for PAH, a specialist clinic, a six-minute-walk endpoint. Cialis 10 to 20 mg PRN is an ED almond. Same enzyme, different dose, different brand, different follow-up. I will not let a man count yellow almonds into a 40 mg pulmonary day. That is how tricks start.
Did the long half-life also explain the later prostate stamp?
Yes. A short PDE5 tablet is a bad chronic urology drug because you would be asking a man to time a prostate symptom that does not punch a clock. Daily 5 mg tadalafil for BPH, 2011, sits on the same steady-state idea as daily ED at 2.5 or 5 mg from 2008. IPSS moves a little. The gland does not shrink. The convenience is real for men who already have both ED and bother. The daily-almond ledger is where I put that overlap. History only explains why the clock made the stamp possible.
Why start at 10 mg and not just give everyone 20 mg the way ads imply?
Because the 2003 label - and the current one - starts most men at 10 mg PRN and lets effect and tolerability push to 20 or pull to 5. Peak is not free. Back ache, headache, and the CYP3A4 ceiling all sit on the higher almond. Ketoconazole or ritonavir: stay at 10 mg and stretch to every 72 hours. Kidneys and liver rewrite the same ladder. I would rather a man have a clean 10 mg night and a planned step than a first-dose 20 mg hangover that poisons the whole class for him.
If Lilly bought ICOS in 2007, does that change anything I should ask my own doctor?
Nothing about the enzyme. The letterhead on a 2003 bottle said Lilly ICOS. The letterhead now says whoever makes your generic almond. Ask your clinician about nitrates, alpha-blockers, ritonavir, ketoconazole, creatinine, and whether you want PRN 10 to 20 mg or a later daily lane - not about who owned a Bothell shop twenty years ago. Ownership is a calendar fact. The spray is a living one.
Where should I read next if I care about proof, not the company story?
Leave this blotter. Open the trial-row note for Brock, Porst, the diabetes rows, and the nitrate pharmacology. Open the medicine page for the labeled map. This history page will not dose you. It will only tell you why a late 10 to 20 mg PRN almond was allowed to exist.
General education from a clinician, not personal medical advice. Bring your own history to your own prescriber.
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