If you are still waiting for a happiness pill to be invented by scientists, you might not have to wait long. It has been less than a decade since the launch of sildenafil citrate (Viagra) - the first oral drug to help men with erectile dysfunctions.

While Viagra is not the first drug to address erectile dysfunction, it is the first drug to be taken orally. Before that, the drugs that were used were either injected directly into the penis, or were inserted into the urethra at the tip of the penis.

After Viagra, new drugs from the same class - vardenafil hydrochloride (Levitra) and tadalafil (Cialis) followed soon. What they have in common is that they are taken an hour before sexual activity, and the chemical reactions they cause lead to increased blood flow in the penis.

They should not be taken more than once a day. They should not be taken at all if the patient takes other drugs, because they might combine to cause blood pressure problems or heart attacks.

Other oral drugs for erectile dysfunction are said to deliver good results, but for now there is no indisputable evidence that the resulting erection is due to them, rather than to the placebo effect. Some of the oral medications (for instance, testosterone) may damage the liver, so erectile dysfunction drugs should not be taken unless prescribed by a doctor.

Drugs which are injected into the penis or inserted into the urethra may lead to stronger and longer erections but they are known for their side effects, such as aching, priapism (persistent erection), bleeding, scarring, etc. And since research is advancing rapidly, it is much better to wait a little longer for a better drug.