Tadalafil - weekend pill.
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In the United States, tadalafil has FDA approval and became available in December, 2003 as the third impotence pill after sildenafil (Viagra) and vardenafil (Levitra). Due to its 36-hour effect it is also known as the weekend pill. It should be noted that the drug has not been formally studied in regard to multiple sexual attempts during a 36 hour period.