When considering herbal therapy it is important to acknowledge some of the age related pharmaco-kinetic and pharmaco-dynamic changes that occur. Safe drug or herb prescribing for older patients has to be based upon an understanding of the changes that occur to absorption, distribution and elimination mechanisms in the aging process. Taking such issues into consideration helps avoid many complications.
Whilst such concerns are not as important for the phytotherapist, they still exist. A brief review of some of the factors involved for both plant extracts and chemical drugs might be helpful. Pharmacological research suggests that the most important issues to consider are:
- ‘Drug’ absorption. For a chemical or plant extract to enter the blood stream when taken by mouth, the absorptive lining of the gastrointestinal tract must be healthy. Medicines must remain in contact with the lining for an adequate amount of time for absorption to occur. There must also be an adequate blood flow to and from the site of absorption.
Normal age related changes impact all of these factors. There is a reduction in mucosal surface area, reduction in blood flow to the intestines and changes in secretions.
- Plasma binding. Plant constituents are transported via the blood once they have been absorbed from the intestines. The more complex molecules are in a form that is often bound with a blood chemical such as albumin. Such protein bound drugs can compete for binding sites, which in turn may have a profound effect upon availability of medications.
- Distribution around the body. With advancing age the proportion of of body water and lean body mass decreases whilst body fat increases. This favors the distribution of fat soluble constituents over water soluble.
- Elimination. The effect of a medicine is ended by it being eliminated from the body or its being changed into some inactive form. This will involve liver metabolism, kidney function, and elimination at other sites around the body. All of these factors become less efficient with age.
As with children, our elders have special needs and plants address these needs. Whenever possible focus upon the tonics and normalizers. The most relevant remedies are pointed out in each section below. Care must also be given to dosage, because of the range of issues touched upon above. In general a lower dosage is used than for younger adults. For details of the standard pharmaceutical formulae used to convert adult dosage to that appropriate for any particular age, please refer to James Green’s Medicine Maker’s Handbook, part of the supplemental reading material.
The main concern is that of ‘paradoxical’ reactions. It is not unusual for medicines to have an opposite effect to that expected with very elderly people. As an example consider that the tranquilizer valium can have a marked stimulating effect upon the nervous system in some elders. This is an unpredictable response, so careful initially careful observation of a patients response is crucial. Be aware of potential paradoxical responses to herbal medications.