A drug’s half-life is the time it takes for 50 percent of the medication’s active ingredient to be eliminated from your bloodstream. It is also virtually identical to the time during which the drug is effective.
In the case of Viagra, the half-life of sildenafil citrate, the little blue pill’s active ingredient, is roughly four hours, which means that the drug is effective for a similar period of time. An individual patient’s response to a drug can vary, and thus in some cases the medication’s half-life is most accurately expressed in a range of time rather than a specific number of hours.
Active Half and Elimination Half
Because it takes two halves to make a whole, the first half of a drug’s so-called life is sometimes referred to as the active half, meaning that the drug is most potent and effective during that period. The second half of the drug’s life is known as the elimination half and refers to the time it takes for the body to flush out all traces of the drug’s active ingredient.
Introduced in 1998, Viagra was the first of a family of drugs that came to be known as PDE5 inhibitors. They are specifically designed to treat erectile dysfunction caused by insufficient blood flow to the penis. As previously noted, the half-life of Viagra is about four hours.
Levitra’s Half-Life Slightly Longer
By contrast, Levitra, the next of the PDE5 inhibitors to win approval by the Food and Drug Administration, has an average half-life of five hours, indicating that its duration of action is slightly longer than that of Viagra.
And compare that with the original formulation of Cialis, approved by the FDA in the fall of 2003, which has a half-life of 17.5 hours, according to an article posted at the website of Boston University School of Medicine.
Individual Responses Vary
Individual responses to a drug’s active ingredient vary, but these figures offer an average of the time it takes for half of the drug’s active ingredient to be eliminated from the body. Individuals who are highly sensitive to a drug’s effects might very well find that the medication’s effects are still being felt well beyond its so-called half-life. For example, many men who take the original formulation of Cialis (tadalafil) have reported that the drug’s effects lasts for up to 36 hours, slightly more than twice the drug’s half-life, earning Cialis the nickname of the “weekend drug.”
Scientifically determined half-lives of medications determine the dosage instructions, particularly of those drugs that are needed to stabilize heart rhythms, blood pressure, and pain management. Because Viagra and the other PDE5 inhibitors lower blood pressure and can interact adversely with some other hypotensive medications, none of them should be taken more than once in a 24-hour period.
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If you regularly use Viagra, its generic equivalent, sildenafil citrate, or another of the PDE5 inhibitors, you should look into the convenience of ordering those drugs online from a trustworthy online facilitator. In business since the late 1990s, eDrugstore.com is just such a supplier. It deals in PDE5 inhibitors, as well as a limited selection of other lifestyle medications, and supplies only FDA-approved drugs, all of them sourced from licensed U.S. pharmacies. To learn more, visit eDrugstore’s Erectile Dysfunction page.
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