buy viagra online canada viagra online cialis drugstore buy cialis online Therefore, the dose and frequency of tadalafil has to be lowered in the following examples:No tadalafil dose adjustment is necessary for men with only mild kidney disease. Men with moderately severe kidney impairment should start tadalafil at 5 mg every 24 hours and not to exceed the maximum dose of 10 mg taken every 48 hours. In men with severe kidney disease and on dialysis, the maximum dose should not exceed 5 mg. Erectile dysfunction (ED), also known as impotence, is the inability to get and maintain an erection that is sufficient for satisfactory sexual intercourse. cialis drugstore cialis online Besides treating the underlying causes such as potassium deficiency or arsenic contamination of drinking water, the first line treatment of erectile dysfunction consists of a trial of PDE5 inhibitor drugs (the first of which was sildenafil or Viagra). In some cases, treatment can involve prostaglandin tablets in the urethra, injections into the penis, a penile prosthesis, a penis pump or vascular reconstructive surgery. Another treatment regimen is injection therapy. One of the following drugs is injected into the penis: papaverine, phentolamine, and prostaglandin E1. One of the forms of phosphodiesterase is termed PDE5. The prescription PDE5 inhibitors sildenafil (Viagra), vardenafil (Levitra) and tadalafil (Cialis) are prescription drugs which are taken orally. They work by blocking the action of PDE5, which causes cGMP to degrade.