That doesn't mean PDE-5 inhibitors are unsafe for everyone, but it does mean that they need to be prescribed and monitored by a doctor.

CNN: Warning: Men's natural sex supplements may not be

For this reason, Pfizer's PDE-5 patent is a bad idea.

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These drugs, known as PDE-5 inhibitors, can cause side effects like headaches, nasal congestion and vision problems -- and they can have dangerous interactions with the heart medication nitroglycerine.

CNN: Warning: Men's natural sex supplements may not be