We have been studying the effect of preadministration of D-phenylalanin (DPA) on acupuncture analgesia for various types of pain. DPA is thought to suppress the activity of carboxypeptidase, which discomposes endorphins. In this double-blind placebo-controled study, clinical effectiveness of acupuncture with DPA preadministration in relieving chronic low back pain was examined.
DPA (4g) or placebo (lactose: 4g) was orally administered to thirty out patients with chronic low back or lower extremity pain 30 minutes before acupuncture treatment. A half of the patients were given placebo in the first session and DPA in the second one, and the other half were given DPA firstly and placebo secondly.
The patients were asked to rate their pain after treatment in comparison with pre-treatment condition. Successful pain relief was obtained in 60% of the patients given DPA prior to acupuncture and in 33.4% of those given placebo. Although it is said that there is a great individual variation in response to acupuncture therapy, this result demonstrates that preadministration of D-phenylalanin enhances analgesic effect of acupuncture therapy.

In previous papers, we experimentally demonstrated the enhancing effect of D-phenylalanine (DPA) administration on the analgesic effect of acupuncture by the increase of pain threshold. In the present study, we examined the effect of administration manners in the patients with chronic lumbago who visited our anaesthesiological department. We conducted a double-blind study with two different administration manners: “previous-day” and “just-before”.
METHODS
Fifty-six patients suffering from chronic low back pain for more than three months were devided into two groups. DPA or placebo was orally administered intwo different manners prior to low-frequency electro-acupuncture treatment. Group I patients (26 cases), took 0.5g three times (i. e. a total of 1.5g): after the evening meal and before go to bed on the day before, and after the beakfast on the day of acupuncture (“previous-day” administration). Group II patients (30 cases), took 4.5g 30 minutes before acupuncture treatment “just-before” administration. The treatment was undertaken twice with DPA administration and twice with placebo administration for each group. “Direct effect” was determined by the number scale method and a comparison between the two groups was made. In the additional experiment, three volunteers were orally given 4.0g or 1.5g DPA, and blood phenylalanine level was determined two hours, four hours and one month later.
RESULTS
In the group I (previous-day administration), “DPA+acupuncture” produced the following result: excellent 7.8%, good 69.2%, moderate 19.2%, (significantly different from placebo administration). In the group II (just-before administration), “DPA+acupuncture” produced the following result: excellent 23%, good 37%, moderate 20%, and no-effect 20% (significantly different from placebo administration). Comparing group I with group II, the percentage of the “excellent” or “good” cases in the former was larger than that of the latter (+17%). Blood phenylalanine level showed its high value 2-4 hours after administration of 4g DPA, whereas 2 hours after that of 1.5g DPA.
Conducting a clinical investigation into the effectual administration (timing and doses) of DPA, we found that previous-day administration is more effective than “just-before” administration in enhancing effect of acupuncture analgesia. Although there is room for further studies with a larger number of cases, considering that DPA has a “slow onset long acting” effect (Ehrenpreis), we can conclude that the series administration of DPA on the day before acupuncture treatment is advisable.

In this research we conducted a comparative study on the pain threshold elevation resulting from “exercise” work loads, ie. running and cycling, and acupuncture anaesthesia. 10 subjects participated throughout our research; whereas, additional subjects only participated in selected experiments. It was found that the pain threshold increased for both exercise work load and acupuncture anaesthesia; however, no significant correlation was found between the pain threshold elevation percentages resulting from exercise work load and acupuncture anaesthesia.
Therefore we propose, although it has been ascertained that the elevation of pain threshold involves the endomorphin mechanism, that there must be other important mechanisms involved as well.