Erectile Dysfunction

Men get an erection (hard on, woody, stiff, etc) for a variety of reasons, one of which is laughing gas. When the penis is happy little gates controlled by nitrous oxide open to let blood flow into the penis to share in the anticipated pleasure. Nitrous oxide closes the gates to the entertainment theatre and the blood remains till the last act releases the audience.  The last 'act' is call an orgasm (yippee, wow, hoorah, yesss).  Viagra acts on the penis nitrous oxide.
About 40 % of men experience erectile failure after the age of 40.  Prior to that men are contending with premature ejaculation and avoiding angry feminists.  One of the main reasons for erectile failure at any time is the condom. This is the age of 'no glove, no love' and 'safe sex'. However this birthcontrol and disease prevention device  reduces the sensation experienced by the male penis.  The female equivalent of erection is lubrication.  Friction causes erection and ejaculation.  Men who are having difficulty with maintaining erection might well try intermittent drying off of the penis.
Another reason for erectile failure is fear.  Men are increasingly afraid in the  modern age that women, especially Swedish women,  increasingly accept dinner, an invitation to bed, take multiple orgasms and call the police when they find out you're a famous Australian publisher wanted by the CIA.
Throughout history,  the big head of men, the general, have been telling the little head, the private, where to go.  Looking back on their experiences, sober,  the generals have to admit they've sent their private into perhaps more than one Charge of the Light Brigade.   Interestingly Homosexual and Heterosexual men will admit to having had poor night time judgement in the light of day. It's not surprising that mutiny can occur especially when alcohol is involved.  Alcohol is probably the principle reason for erectile failure but it's also the only reason men would consider having sex with some of those  they have sex with.
Viagra comes in 25, 50 and 100 mg tablets.  It retails for about $10 a tablet regardless of tablet size.  It's best to start with a 50 mg tablet and cut it in two.  If you are in the intensive care unit after triple bypass surgery and the nurse is especially cute you might start with a 25 mg tablet, cutting that in two.  The Viagra experience is about 4 hours and it takes 1/2 to 1 hour to begin to work.  The principal side effect is facial flushing and often a headache which responds well to aspirin.
When Viagra was first advertised by the manufacturers they made a lot of todo about "priapism'.  Priapism is a painful persisting erection in which the gates that hold the blood in the penis don't open and the lack of new oxygen can in time cause the penis to become gangrenous and fall off. The warning didn't go into this much detail. It just said, If you experience an erection that lasts too many hours you should go to the nearest emergency.  Men being what men are it's since been estimated that the 'warning' accounted for 30% of sales.
Cialis is another wonder drug made by God for the old fart.  As one aged feminist said, "why put a new flagpole on a condemned building."  It makes the building happy, old men responded, between lapses of alzheimer's.  Women don't like holding garden hoses anymore than vacuums whereas ever since Salem everyone knows they're partial to holding broom handles..
Cialis lasts about 36 hours.  It comes in 5, 10 mg and 20 mg tablest and costs about $10 a tablet.  Naturally it's competitive with viagra.  I never start people on cialis, even young athletes with young insatiable girlfriends.  If a person were to turn purple with green spots all over their armpits viagra would flush out of the system that much faster than cialis.
The other major reason for viagra and cialis is other medications.  A wide range of medication causes men to wilt. Almost any medication can turn a man off.  Paroxetine, the antidepressant is particularly bad for maintaining erections. All the SSRI's can reduce sexual desire and erection potential. Ginkgo Biloba  was the first drug shown to counteract this tendency of the antidepressants but viagra works like a charm.  Interestingly viagra can counteract the reduced sexual desire women can experience with medications like SSRI's but by itself viagra doesn't improve female sexual function if it's not being used to counteract another medication.
Cialis has been used at 5 mg a day for five days in a row by itself to improve erections or coupled with more cialis on the weekend in particularly resistant cases.  The advantage of low dose viagra is safety and less side effects.
A seventy five year old man really did come into my office and ask for viagra. I gave him 10 50 mg tablets and suggested he cut them in half.  He returned to see me for something else a few months later and I asked how the viagra worked. He said he and his wife loved it. It was great after years without having sex and they were glad for the fun they had using up all 10 of the tablets. I asked him if he wanted anymore and he shook his head. "Not right now.  My wife and I  are on a fixed budget. We discussed it. We can either go to a movie or have sex once a week and we decided that we'd rather go to a movie."
Personally  I find that I'm of an age and work is so stressful that I can go out and dance all night or stay home and have an erection, but I can't do both..  There's a lot to say for morning and afternoon sex on weekends after a light lunch and a fine cup of tea with a willing woman who thinks sex is plain good fun at any age.