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.
An additional question mark for Cialis: It inhibits another phosphodiesterase enzyme, PDE-11, which is found in the testicles and the heart, although the Lilly-Icos team insists studies show no problems.
The PDE immediately switched over to a back-up chain, and it also shut itself down just in case the anomaly was a problem in the electronics rather than in the physical system itself.
The problem came to light when a Propulsion Drive Electronics (PDE) control unit picked up a difference in pressures between the oxidiser and the fuel going through one of the ATV's four "propulsion chains".