Hyperkalemia is a common side effect of these medications. GI disturbances, including nausea, vomiting, diarrhea, anorexia can occur. Triamterene and spironolactone have been known to cause impotence and sexual dysfunction. Spironolactone may precipitate gynecomastia or an SLE-like syndrome.
Flexeril has a half life of 18 hours. So 5x18 is 90 hours. Or just under 4 days. Of course, it is not that easy. This varies on how much and how long the drug was taken and it can vary from person to person. That being said I cannot image any way that flexeril would be detectable 30 days after the last dose.
Flexeril is not usually prescribed to children under 15 years of age. It is rarely used among patients over 65 years old, because it increases drowsiness and their risk for falls. Elderly bodies also take longer to metabolize and eliminate drugs, allowing them sometimes to build up to unhealthy levels.