Erectile dysfunction (ED) is a medical term that describes the inability to achieve and or maintain an erect penis adequate for sexual intercourse. It is one of the most common sexual problems for men and the chance of developing it increases with increasing age. It is also commonly seen in men with other medical conditions, such as diabetes and heart disease.
Achieving a normal erection is a complex process requiring adequate inflow of blood into the penis, a normal nerve supply to the penis, a normal structure to the penis, and adequate levels of the male sex hormone testosterone. All of these factors have to be present for men to get an erection, and of course there has to be a psychological stimulus to get an erection as well. Any abnormality in any of the above, whether caused by another medical condition or medication used to treat other conditions, can cause impotence.
The most common medical conditions causing ED are diabetes, high blood pressure, high blood cholesterol, and cardiovascular disease. Other conditions associated with ED include neurologic disorders such as multiple sclerosis, benign prostatic enlargement , and depression. Other conditions associated with reduced nerve and blood flow include aging and smoking.
Low levels of circulating testosterone may cause ED, although low testosterone is found in a minority of men who develop ED. Low levels of sexual desire, lack of energy, mood disturbances, loss of muscle strength and depression can all be symptoms of low testosterone. A simple blood test can determine if the testosterone level is low.
As well as smoking, drug or alcohol abuse, particularly over a long period of time, will compromise the blood vessels of the penis. Lack of exercise and a sedentary lifestyle will contribute to the development of ED. Modifying these risk factors may contribute to overall health and may in some individuals correct mild ED.
Treatment of many medical conditions can interfere with normal erections. Drugs used to treat some of the risk factors listed above may also lead to or worsen ED. Antihypertensives (drugs used to treat high blood pressure), diuretics, and digoxin may cause ED, as may those drugs used to treat various psychiatric problems (eg: antidepressants). Steroids, drugs used to treat enlarged prostates (benign prostate enlargement) such as finasteride or dutasteride, or prostate cancer (eg: injection therapy with zoladex or prostap, or antiandrogens) can also all cause ED. Patients undergoing surgery or radiation therapy for cancer of the prostate, bladder, colon or rectum are at risk for the development of ED.
For most patients, the diagnosis will require a medical history, physical examination including blood pressure, examination of the penis and testes, and a rectal examination. A few routine blood tests are done in all patients, and include a measurement of blood lipids, glucose and testosterone. More blood tests may be required if any of these are abnormal. The choice of testing and treatment depends on the goals of the individual. If erection returns with simple treatment like oral medication and the patient is satisfied, no further diagnosis and treatment are necessary. If the initial treatment response is inadequate or the patient is not satisfied,then further steps may be taken. In general, as more invasive treatment options are chosen, testing may be more complex.
The first line of therapy for most patients with ED is use of oral medications known as phosphodiesterase 5 (PDE 5) inhibitors. These include sildenafil (Viagra), vardenafil (Levitra) or tadalafil (Cialis). Men with ED take these pills before beginning sexual activity and the drugs boost the natural signals that are generated during sex, thereby improving and prolonging the erection itself. These medications are safe and often effective, with improvement in erection in nearly 80 percent of patients using these drugs. Early concerns about possible bad effects on the heart have largely been dispelled, though clearly if patients resume sexual activity after some time and have bad angina where physical activity is contraindicated then they should not use PDE5 inhibitors. They must also be avoided in those patients using medications called nitrates because of an interaction between these two classes of drugs.
Table of the differences between sildenafil, vardenafil and tadalafil.
| Drug | Sildenafil (Viagra) | Vardenafil (Levitra) | Tadalafil (Cialis) |
| Dose | 25, 50, 100mg | 5, 10, 20mg | 10, 20mg |
| Duration of onset | 30–60 minutes | 30–60 minutes | 30–60 minutes |
| Half life | 4-6 hrs | 4-6 hrs | 16-18hrs |
| Cautions | Patients taking nitrates, retinitis pigmentosa | Patients taking nitrates, retinitis pigmentosa | Patients taking nitrates, retinitis pigmentosa |
| Absorption | Affected by fatty foods | Affected by fatty foods | |
| Side effects | Headache, facial flushing, nasal stuffiness, dyspepsia, transient visual symptoms | Headache, facial flushing, nasal stuffiness, dyspepsia, transient visual symptoms | Headache, facial flushing, nasal stuffiness, dyspepsia, muscle ache |
The main differences between the medications are that tadalafil is longer acting. It is now available in a daily dose formulation, where patients take 5 mg each day.
The side effects of PDE 5 inhibitors are mild and usually transient, decreasing in intensity with continued use. The most common side effects are headache, stuffy nose, flushing and muscle aches. In rare cases, sildenafil can cause temporary changes in blue-green colour vision. This is of no long-term risk and is gone within a short time as the amount of sildenafil in the blood decreases. It is important to follow the instructions for using these medications in order to get the best results. Tests have shown that 40 percent of men who do not respond to sildenafil will respond when they receive proper instruction on medication use.
For men who do not respond to oral medications another drug, alprostadil, is approved for use in men with ED. This drug comes in two forms: injections that the patient places directly into the side of the penis and as an intraurethral pellet formulation (MUSE). Your doctor will be able to discuss with you whether these are suitable. The most common side effects of alprostadil use are a burning sensation in the penis and a prolonged erection lasting over four hours, requiring medical intervention to reverse the erection. This latter side effect is an emergency, and if it occurs you need to seek medical help urgently.
For men who cannot or do not wish to use drug therapy, an external vacuum device may be acceptable. This device combines a plastic cylinder or tube that slips over the penis, making a seal with the skin of the body. A pump on the opposite end of the cylinder creates a low-pressure vacuum around the erectile tissue, which results in an erection. To keep the erection once the plastic cylinder is removed a rubber constriction band goes around the base of the penis, which maintains the erection. With proper instruction, 75 percent of men can achieve a functional erection using a vacuum erection device.
For a very small number of patients, placement of a penile prosthesis or “implant” will be the only option. Your doctor will be able to discuss this with you.
The above drugs may only be prescribed on NHS prescriptions for the treatment of erectile dysfunction to men who:
Men who fall outside of these restrictions and are therefore not eligible for an NHS prescription, may be issued with a private prescription by their GP. GPs are not entitled to charge for writing a private prescription for these drugs. NHS prescriptions must be endorsed ‘SLS’ by the prescriber which verifies that the patient falls into one of the above categories.
If you are consulting Cambridge Urology Partnership because of your ED we will only be able to write you a private prescription.
More information is available in brochures for patients provided by the AUA foundation:
Erectile Dysfunction: Causes, Risks & Talking To Your Doctor
Erectile Dysfunction: Primary Treatment Options
Erectile Dysfunction: Secondary Treatment Options
