Over the years a number of people have posted saying that their drugs have suddenly become less effective. Sometimes this has been linked to a move to generics. The suspicion has been that quality control has not been good enough.

I suspect that the effect of taking levodopa based drugs is especially affected by variations, both high or low, in the actual doses of the active component drugs. This could show itself in not crossing the "on"/"off" threshold or in increased dyskinesia. It could also be noticed in term of a dose wearing off earlier. On a three hour drug cycle a 5% lower dose would finish about 10 minutes earlier.

Ideally we could benefit from a full chemical analysis of each pill. But, not having the equipment to do that job, I thought we could make a start by accurately weighing tablets.

The whole weight of a tablet includes the filler, so you can't conclude that high figures are good and low figures are bad. Depending on the relative densities of the filler and the active ingredients, and possible oxidation going on, it could work either way. However, I think it is reasonable to expect a low variation in the tablet weights, both intra-batch and inter-batch.

The measurements below are raw (uncalibrated) weights (mg) of Stalevo tablets (levodopa 75, carbidopa 18.57, entacapone 200). 5 tablets were weighed from each of two batches. Each tablet (A to E) was weighed 3 times. The pills came from unopened plastic pill tubs, with a foil cover.

Batch 1742670
Expiry 04/2019
A, 530, 532, 531
B, 543, 544, 543
C, 538, 538, 537
D, 531, 530, 531
E, 521, 522, 524

Batch 1824362
Expiry 09/2020
A, 528, 526, 526
B, 519, 521, 520
C, 521, 521, 522
D, 526, 526, 524
E, 522, 522, 520

As a rough analysis, I will do a proper statistical analysis later, taking the middle result as the true weight of each pill and then taking the difference between the highest and lowest value gives:
Intra-batch
Batch 1742670, range = 21mg, about 4%
Batch 1824362, range = 6mg, about 1%
Inter-batch, range = 23mg, about 4%

As a calibration measure, though the above results use raw figures.

50 gm weight
Before 50149, 50148, 50144
After 50142, 50147, 50141

1p UK coin, nominal 3560
A, 3573, 3570, 3575
B, 3546, 3547, 3547
C, 3540, 3531, 3531

5p UK coin, nominal 3250
A, 3268, 3265, 3265
B, 3277, 3273, 3272
C, 3293, 3299, 3297
(The coins were not of mint condition.)

I used a digital scales, 8028 series. Available on eBay for about £10. If you want to look into this area, you want a scales that measures "0.001 g", i.e. a mg.

John