I have been taking diclofenac for years now, varying between 100mg, to 150mg
a day. There have also been times where I have had to temporarily stop
taking it when I had a stomach flu and the Dr. prescribed something for the
flu that conflicted with the diclofenac. What I can tell you from this is
that diclofenac builds up in the body system over time and the longer you
stay on the medication the better it works. If you stop taking it, even
temporarily, it once again takes some time before it builds up enough in the
body system to work at its most effective. But once it has built up in the
body you can reduce your dosage and still receive the bets effects from the
medication. I can also tell you that if you have to take cholesterol
lowering medication as well, like I do, the dosage of these two different
medications will cause liver problems if not monitored carefully. For
instance: the most effective dosage of diclofenac for me is 75mg twice a
day, and the most effective dosage of cholesterol lowering medication is
20mg of Zocor. But the two in combination always raises my hepatitis B liver
count to unhealthy levels. So currently I am working with my Dr. to try and
find a combination of the two meds that works, yet doesn't raise my liver
count.

DCT

It usually starts to kick in at about one hour for me and is really having an
effect at 90-120 minutes - I take only the standard stuff, twice/day.  
But...... everyone's different.  The 50 mg tabs definitely aren't
slow-release as well?  You might let your doc know it's taking it do long to
kick in.  He might be able to give you something else to take during the day.

Puckertoe.

I have been taking diclofenac retard for years (100 mg daily). My
experience is similar to yours ie taken at breafast time, it takes
around 3 hrs to show any effect. This may not be totally a drug effect.
Remember that in the case of rheumatoid patients there is a natural
progression thro the day, and these people are generally at their best,
late morning until early afternoon. Fatigue can occur in the mid pm and
maybe they feel better for a while in the evening.

Elimination half life is stated as 1.2 - 3hrs (slow release spreads the
release over a longer period and the effect of a single dose is much
longer than the half life) - See
http://en.wikipedia.org/wiki/Diclofenac
Max dose seems to be 150 mg daily, but 100 mg more usual.
My own experience is that a single 100 mg retard tablet is effective
for about 18 hrs.
I think, also, that increasing effectiveness over several days may be
due to the drug's progressive damping effect on inflammation rather
than to a continual build up in the body. Blood test have always been
part of my treatment. I also get occasional gut problems.

Peter