Nitrofurantoin (100mg-type) OVERDOSE

A white male, aged 63, on the 4th day into a typical 7-day (2-pills-per-day) regimen of "NITROFURANTOIN MONO/MACRO 100MG" for a routine urinary tract infection, I mistakenly took THREE of said 100mg pills in one 14-hour period.  To wit, on said 4th day, I took the FIRST pill at 6 a.m., the SECOND pill at 6 P.M., and the THIRD pill (dumbly) at 7:30 p.m., or one-&-one-half hours AFTER that second pill.  I had FORGOTTEN that I had, in fact, already TAKEN that SECOND daily pill.  (With this old man, I don't forget to "do" things, I forget that I have indeed DONE them!!!)  QUESTION:  Other than the DIARRHEA I experienced the morning immediately FOLLOWING said overdose, could those 2-pills-at-the-same-time have, nonetheless, done some signifcant (but as yet un-detected) DAMAGE to any of my principal bodily organs/tissues????  THANKS for any general information about this.  I have posted this question, because the "product information" on said "Nitro" drug warns that TWO (100mg) pills should NOT be taken at the SAME time.  (END OF POST)