Dissolution Testing
The United States Pharmacopeia Convention (USP) is currently preparing monographs to define the quality of herbal supplements. Most of the herbal monographs that have been published so far by the USP (in Pharmacopeial Forum, preliminary to publication in the USP National Formulary) have dissolution requirements. Most ethical drugs are also required to meet USP dissolution requirements. In contrast to disintegration, which evaluates only tablet appearance, dissolution refers to the ability of products to release specific active or marker compounds into a medium that is designed to adequately simulate the gastrointestinal tract. In many instances, tablets can completely disintegrate while releasing little of the active compounds, due to adherence to tablet particles and other reasons. Hence, measuring the dissolution release for herbal supplements is becoming essential for determining product quality. Plant Bioactives offers the following dissolution assays:
Dissolution of Garlic Supplements
Garlic is one the most important plants for which supplement dissolution testing is critical to evaluating quality. In fact, a recent examination of 24 brands found that most garlic supplements do not release more than 10% of their label claim for allicin, due in large part to certain tablet excipients that interfere with allicin formation and release.
Plant Bioactives measures allicin release according to USP method 724A, as described in Pharmacopeial Forum 2000, 26 (5), pp. 1354-1357. Passing the test requires that six out of six tablets release at least 80% of the label claim for allicin, after being incubated in acid for 2 hours and in intestinal buffer for 1 hour. If one or more of the six tablets fails to do so, then another six tablets must be tested and the average of all twelve tablets must release at least 75% of label claim with no tablet releasing less than 60% of label claim.
Because a dissolution apparatus can only accommodate 6-8 tablets, only a single lot can be tested at one time for meeting the method requirement. As an economical alternative during product development, before doing a final test of six tablets per lot, Plant Bioactives will test 2-4 lots of 2-4 tablets (6-8 total tablets) per lot for only 15-36% more cost than testing a single lot.
Dissolution of Other Herbal Supplements
The Pharmacopeial Forum monographs, published by the USP, currently have dissolution requirements for the following:
- Ginkgo
- Valerian
- Milk thistle
Furthermore, the USP has announced that monographs are under development for the following:
- Black cohosh
- Cat's claw
- Chastetree
- Red clover
Plant Bioactives will be able to perform dissolution testing for each of these plants, as soon as the requirements for each are published.
Dissolution of Multi-vitamins
The 2000 USP now requires water-soluble multi-vitamin tablets and capsules to meet dissolution specifications for folic acid (if present) and one other index vitamin, in the following order or priority, if present:
- Riboflavin
- Pyridoxine
- Niacin
- Thiamine
- Ascorbic acid
