Sildenafil (Viagra®) will soon face competition: Tadalafil has applied for approval in Europe and the US. Tadalafil is said to have a more selective effect on type 5 phosphodiesterase in the penis. The effect occurs quickly and persists for over 24 hours.
Five to seven million men in Germany suffer from erectile dysfunction. The incidence increases with age.
Many organic causes
A non-negligible proportion of erectile dysfunction is psychologically (with) caused. Among the organic causes is the damage of nerves, for example by spinal cord injuries, operations (eg radical prostatectomy) or in multiple sclerosis. Especially common is erectile dysfunction (= ED), an early symptom of underlying vascular diseases (hypertension, atherosclerosis, diabetes mellitus, coronary heart disease). Over 75% of male heart attack patients already have erectile dysfunction five to seven years before infarction. Hormone deficits, overactive or underactive thyroid glands, medicines (eg antihypertensives, antidepressants, digitalis glycosides, neuroleptics), nicotine, alcohol and drugs can also cause erectile dysfunction.
There is a great need for education
The need for education on erectile dysfunction is great. The Information Center for Sexuality and Health e.V. offers
the possibility of telephone inquiries about sexual dysfunctions on 01 80/5 55 84 84 from Monday to Friday from 15 to 20 o’clock
Information under the Internet address www.isg-info.de About 200 calls arrive here daily, whereby most questions concern erectile dysfunctions. About 400 people visit the website every day.
Of the more than 9000 visitors to the website who completed a questionnaire on the risk profile of erectile dysfunction, nearly 80% did not know their underlying condition accurately. There is also a need for information on treatment options for erectile dysfunction.
Various therapy options
- The therapy spectrum includes: psychotherapy, partner therapy
- Local treatment: injection of alprostadil (prostaglandin E1) into the cavernous body (cavernous autoinjection therapy, SKAT) or use as a gel in the urethra
- Vacuum erection aid
- Oral treatment: yohimbine, the phosphodiesterase inhibitor sildenafil, apomorphine
- Schwellkörperimplantate (as a last resort, then no natural erection more possible)
Two new phosphodiesterase inhibitors
The spectrum is expected to expand to include two oral therapeutics: the phosphodiesterase inhibitors tadalafil (IC351) and vardenafil (Bay 389456). Both have undergone Phase III clinical trials. Tadalafil by Lilly ICOS has already been submitted for approval to the FDA and the European regulatory agency EMEA for the indication of erectile dysfunction.
Tadalafil: more selective and longer effective
Tadalafil has been evaluated in studies involving more than 5,000 patients, including eight Phase III studies. It differs in its chemical structure from sildenafil, but also inhibits the phosphodiesterase type 5 (PDE-5). PDE-5 breaks down in the cavernoskeletal cGMP. The second messenger cGMP allows the smooth muscle of the erectile tissue to relax, allowing more blood to flow into the penis. Therefore, sufficient cGMP concentration is required for tumescence (= swelling) of the penis.
Tadalafil attacks more selectively on type 5 phosphodiesterase than sildenafil; the affinity for PDE-1 in the heart and PDE-6 in the retina is reduced. That under Tadalafil only in individual cases Farbsehstörungen have occurred, may be related to the increased selectivity.
The half-life of tadalafil is 17.5 hours longer than that of other PDE-5 inhibitors (sildenafil 3.5 hours and vardenafil 3.9 hours). The effect of Tadalafil persists for 60% of users over 24 hours.
The maximum drug concentration in the plasma is reached only after 120 minutes (70 minutes with sildenafil, 40 minutes with vardenafil), but the effect often occurs after 15 to 30 minutes: in one study, one third of the men was already 16 minutes after the Ingestion and after sexual stimulation erectile.
The standard dose is 20 mg. There are no guidelines for the duration of treatment; the patient himself decides when the treatment can be over. In psychogenic ED, it sometimes suffices for the patient when the tablet is in the drawer.
The clinical studies showed that tadalafil helps regardless of the severity and duration of erectile dysfunction and also regardless of the patient’s age. For example, a Canadian study of 212 ED patients who used Tadalafil when needed showed dose-related (2, 5, 10, or 25 mg) erection improvement in up to 88% of cases. Up to 73% of the coitus experiments were successful, that is, until ejaculation was performed.
The “worst case” of erectile dysfunction with mostly severe organic disorders is in diabetics. In a Spanish study of 216 diabetics with ED, tadalafil dose-dependently (10 or 20 mg) improved erection in almost two-thirds of patients.
Only mild to moderate side effects
As side effects dominate headache, dyspepsia, back and muscle pain, which are usually mild to moderate in severity and decrease in the course of ingestion. Color vision disorders, as known by sildenafil, occur only in isolated cases. So far, no serious cardiovascular side effects are known.
Source Dr. Viola Bronsema, Bad Homburg, Priv.-Doz. Dr. Gralf Popken, Berlin, Dr. med. Axel-Jürg Potempa, Munich, Prof. dr. Hartmut Porst, Hamburg, Press Conference “IC351 – a new, advanced PDE-5 inhibitor for the treatment of erectile dysfunction”, Dusseldorf, September 20, 2001, hosted by Lilly ICOS.
Viagra will soon face competition: Tadalafil has been applied for approval in Europe and the US. Tadalafil is said to have a more selective effect on type 5 phosphodiesterase in the penis. The effect is rapid and lasts for over 24 hours. Vardenafil has been submitted for regulatory approval in the US and Mexico.