Viagra leads as rivals are moving up.
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Mitka
D004345:Drug Industry; D007172:Erectile Dysfunction / Q000188:drug therapy*; D006801:Humans; D008297:Male; D010726:Phosphodiesterase Inhibitors / Q000627:therapeutic use; D010879:Piperazines / Q000627:therapeutic use; D011687:Purines; D000068677:Sildenafil Citrate; D013450:Sulfones
D010726:Phosphodiesterase Inhibitors; D010879:Piperazines; D011687:Purines; D013450:Sulfones; D000068677:Sildenafil Citrate