PDE5 inhibitors - Viagra and other drugs against erectile dysfunction

Most men know PDE5 inhibitors as Viagra. They play an essential role in the drug therapy of erectile dysfunction. However, PDE5 inhibitors are by no means suitable for all men. And even if so: Sildenafil (Viagra), Tadalafil (Cialis) and Co. are only effective in about 50 percent of cases of erectile dysfunction?


What are PDE5 inhibitors?

PDE5 inhibitors are a group of prescription drugs that are mainly used in the therapy of erectile dysfunction. Medical practitioners refer to PDE5 inhibitors as phosphodiesterase-5 inhibitors. The term PDE5 inhibitors is derived from its functionality. In colloquial language PDE5 inhibitors are mainly known under the label Viagra. Viagra was the first PDE5 inhibitor launched on the market 20 years ago. Originally, its active ingredient was developed for the treatment of hypertension and complaints of breast tightness (angina pectoris). Today, Sildenafil is mainly used for erectile dysfunction and pulmonary hypertension.

Mode of action of PDE5- inhibitors

The effect of the various PDE5 inhibitors is based on the same principle. They deactivate the enzyme phosphodiesterase-5 (PDE-5). Hence, the term PDE5 inhibitors. The enzyme PDE5 plays an important role for erections. First and foremost, it breaks down the messenger substances that lead to the flaccid status of the penis. Read more about how to achieve and maintain an erection here: How do erections occur? Just this much here:

  • PDE5 inhibitors do not causally induce an erection. They ensure that a latent existing erectile capacity is improved. This is especially true for the strength and duration of the penis hardening
  • The effectiveness of PDE5 inhibitors presupposes sexual arousal. PDE5 inhibitors improve the stimulus transmission. If, for example, this is suppressed by medication (e.g. antidepressants) the erection will not occur despite the intake.
  • If the nerves supplying the penis are disturbed, sexual arousal does not arrive as an impulse for erection - and the effect of PDE5 inhibitors cannot unfold.

Drug therapy with PDE5 inhibitors is the most common – and very successful – form of treatment of erectile dysfunction. However, only have of all men respond to these drugs. In particular men who do not tolerate PDE5 inhibitors very often benefit from shock wave therapy for erectile dysfunction. Another alternative is the stent implantation for erectile dysfunction.


Side effects of PDE5 inhibitors

In otherwise healthy men with erectile dysfunction the side effects of PDE5 inhibitors are usually limited to impairment of well-being. Headaches, dizziness, runny nose and facial redness as well as gastrointestinal complaints are among the most common adverse effects. Particularly Sildenafil and Vardenafil often cause disturbances in color vision. Less frequent, but also much more uncomfortable, are possible back and nerve pains. In addition, sometimes erections lasting for hours can occur which can be very painful (priapism).

Cases of death due to Viagra?

After the launch of PDE5 inhibitors two decades ago, there were repeated reports of fatal complications after the intake of Sildenafil. After more detailed investigations, it turned out that the PDE5 inhibitors alone could not be held responsible for these cases of deaths. The victims were rather men who had taken PDE5 inhibitors in combination with other active ingredients. Accordingly, there is a particular mortal danger if PDE5 inhibitors are combined with nitrite-containing sexual stimulants (poppers such as amyl nitrite, butyl nitrite and isobutyl).


For whom are PDE5 inhibitors not suitable?

Men with cardiovascular diseases such as coronary heart disease (CHD), myocardial insufficiency and cardiac arrhythmia generally should only take PDE5 inhibitors after a detailed medical consultation. The same applies to patients with thrombosis, heart attack and stroke in their anamnesis. Primarily, it has to be clarified whether the physical exertion during sex is tolerable at all - or whether it could overtax the heart.

Under no circumstances should PDE inhibitors be taken in combination with certain cardiovascular drugs. This particularly applies to nitrates, beta-blockers, calcium channel blockers and molsidomin, which are used among others for the prevention and treatment of chest tightness (angina pectoris) and/or high blood pressure.

Further interactions

In addition, there are interactions with other active ingredients. These include, for example, the antiepileptic drugs carbamazepine, phenytoin and phenobarbital as well as the mood-enhancing herbal antidepressant St. John's wort. These active ingredients accelerate the degradation and excretion of PDE5 inhibitors - with a correspondingly shorter duration of effectiveness and lower potency.

Other active ingredients prolong the degradation and excretion of PDE5 inhibitors and in some cases considerably raise the potency - up to the life-threatening overdoses. These are mainly active ingredients from the group of antibiotics such as clarithromycin and erythromycin, the antifungals itraconazole and ketoconazole, saquinavir for the treatment of HIV infections or cimetidine for heartburn. Even grapefruit juice can cause an overdose of PDE5 inhibitors.

Therefore it is of crucial importance to inform the physician about all medication used (even drugs obtainable without a prescription) before prescribing PDE5 inhibitors.


Black market: Do not buy any PDE5 inhibitors online

PDE5 inhibitors are very effective medications that entail risks. So they are only available on prescription for a good reason. If you buy PDE5 inhibitors without a prescription online you are taking incalculable risks for your health. This is not only true with regard to possible side effects or interactions (with other medication). Much more dangerous is that medication from the black market or from abroad is not subject to effective control. At best, you spend a lot of money on pills free of active ingredients. In the worst case, you swallow a cocktail of active ingredients adulterated by reckless businessmen. On top of it: If you are caught with illegally imported PDE5 inhibitors, you are liable to prosecution.

The Swiss Medicines Agency Swissmedic has also been warning for years against supposedly harmless herbal PDE5 inhibitors as offered on the Internet. Synthetic PDE5 inhibitors have been found in many of these products.

Your partner for the therapy of erectile dysfunction

Six questions for Dr. Diehm:

Prof. Dr. Diehm answers eight frequently asked questions about erectile dysfunction (German)

Do you have any questions?

At the Institute for Erectile Dysfunction you find qualified dialog partners for all questions on erectile dysfunction. If you have any questions or would like to make a consultation appointment: Call us: +41 62 824 02 42 or write an e-mail to info@erectiledysfunction-treatment.com