Analgesic and anti-inflammatory compositions

Analgesic and anti-inflammatory compositions are provided which comprise a therapeutically effective amount of a first agent selected from the group consisting of D-phenylalanine, DL-phenylalnine, D-leucine, and DL-leucine and synergistically effective amount of a second therapeutic agent selected from the group consisting of aspirin and an aspirin-type non-steroidal anti-inflammatory, anti-pyretic agent.

FIELD OF THE INVENTION 
This invention relates to analgesia, and/or inflammation, and more 
particularly relates to pharmaceutical compositions employed in treating 
pain and/or inflammation and which comprise a combination of a first 
therapeutic agent selected from the group consisting of D-phenylalanine, 
DL-phenylalanine, D-leucine, DL-leucine and hydrocinnamic acid and a 
second therapeutic agent selected from the group consisting of aspirin and 
a non-steroidal, aspirin like anti-inflammatory, antipyretic agent. 
BACKGROUND OF THE INVENTION 
Enkephalins and endorphins are morphine-like substances which have recently 
been discovered to be endogenous in various animal species, including 
mammals and man, and serve as the body's natural pain relievers. 
Enkephalins and endorphins are peptides and/or polypeptides. Enkephalins 
are normally present in the brain. 
It has heretofore been observed that enkephalins and endorphins have an 
ability to act as analgesics to abolish pain when administered to various 
animals by certain special routes (e.g. directly into the brain) which 
pose practical drawbacks to useful administration. Further, these 
substances have a serious drawback in that they are addicting, and 
tolerance develops to them. In addition, they have an effect of very short 
duration of action when administered to mammalian hosts, due to their 
rapid destruction by other substances endogenous to animal species, 
including mammals and man. These endogenous substances that destroy the 
action of enkephalins were originally believed to include at least two 
known enzymes, carboxypeptidase A and leucine aminopeptidase. It was since 
learned, however, that carboxypeptidase A is not involved in the 
destruction of the enkephalins and endorphins. 
Regardless of the endogenous substances responsible for the destruction of 
enkephalin when isolated or synthesized and administered to mammals, in an 
attempt to overcome the problem, various derivatives of enkephalin, the 
endorphins and other beta-lipotropin fragments 61-91 were synthesized, and 
reported in the literature. Based on earlier successful attempts by Coy 
and Schally to block enzymatic degradation upon administration of LHRH 
leutinizing hormone by replacing a naturally occuring amino acid in the 
naturally occuring peptide sequence with a D-amino acid, D-alanine, and 
other D-amino acids including D-leucine and D-phenlylanine, were 
introduced into the amino acid sequence of enkephalin and other 
beta-lipotroprin fragments 61-91 in place of the naturally occuring 
glycine in the 2-position, or other naturally occuring L-amino acids in 
the naturally occuring amino acid sequence. Other modifications were 
investigated, but none of these derivatives have met with commercial 
success despite the concerted efforts of investigators at a number of 
major pharmaceutical companies, universities and government agencies. None 
of these derivatives have met with commercial success, and the treatment 
of moderate to severe acute and chronic pain still requires administration 
of potent analgesic agents such as codeine, propoxyphene, demerol, 
morphine and the like. 
Thus, a need remains for analgesic agents which provide relief from acute 
or chronic moderate to severe pain which can not be treated with aspirin, 
aspirin-like non-steroidal anti-inflammatory agents and acetominophen. The 
present invention fulfills the long-standing need for safe, effective 
analgesic agents which can be used in in the treatment of moderate to 
severe, acute or chronic pain. 
D-phenylalanine, DL-phenylalanine, D-leucine and hydrocinnamic acid are 
known chemicals listed in the Merck Index. 
Use of D-phenylalanine has been reported from the Faculty of Medicine, 
Buenos Aires, Argentina in Therapy of Depression by Phenylalanine" Arzneim 
Forsch, Vol. 25, NR1 (1975), and "Use of D-Phenylalanine in Parkinson's 
Disease", Arneim Forsch, Vol. 26, NR4 (1976). In the report of treatment 
of depression, DL-phenylalanine was administered in quantities of 50 or 
100 mg per day for 15 days, and D-phenylalanine was administered in the 
amount of 100 mg per day for 15 days. 
A commercial drug, sold under the Trademark "Deprenon", is available for 
treatment of depression by oral ingestion of 3-4 capsules per day. 
Deprenon's specifications states that each capsule contains: 
______________________________________ 
D-Phenylalanine- 50 mg 
Mannitol 90 mg 
Pervidone 4 mg 
Magnesium stearate 3 mg 
______________________________________ 
Leucine and phenylalanine are also known to be useful as nutrients. 
BRIEF SUMMARY OF THE INVENTION 
The present invention provides compositions which are useful in the 
treatment of pain and/or inflammation comprising a therapeutically 
effective amount of an analgesic, anti-inflammatory agent selected from 
the group consisting of D-phenylalanine, DL-phenylalanine, D-leucine, 
DL-leucine and hydrocinnamic acid, and a synergistically effective amount 
of a potentiating agent selected from the group consisting of aspirin and 
a non-steroidal, aspirin-type anti-inflammatory, anti-pyretic agent. 
The first therapeutic agents constitute an entirely new class of 
analgesics. The most potent of these agents is D-phenylalanine. 
Hydrocinnamic acid and D-Leucine have also been found to have a 
significant effect. The combination of D-phenylalanine and D-leucine has 
proven to result in a potentiation of the analgesic activity of either 
substance alone. The chronic and non-chronic administration of 
D-phenylalanine and D-leucine has produced very long-lasting analgesia in 
mice. 
Each of the foregoing substances is available in a powder form and is water 
soluble. DL-phenylalanine (a mixture of D-phenylalanine and 
L-phenylalanine) and DL-leucine (a mixture of D-leucine and L-leucine) may 
be economically used, respectively, as a source of D-phenylalanine and 
D-leucine whose utility is disclosed herein. The DL-form of those two 
chemicals is less expensive than the pure D-form of those two amino acids. 
The analgesic characteristics of the new class of substances were 
determined by examining animal reaction to a single treatment, referred to 
as an "acute" experiment or test, and also to prolonged administration, 
referred to as a "chronic" experiment or test, to determine if tolerance 
develops. 
The analgesic effect of the new class of substances is enhanced or 
potentiated by combining the substance with an anti-pyretic, 
anti-inflammatory analgesic agent such as aspirin or an "aspirin-type" 
drug. The terms "aspirin-type anti-inflammatory agent" "aspirin-like drug" 
or "aspirin-type drug", or "an anti-pyretic, anti-inflammatory agent of 
the aspirin-type" are all synonomous as used herein, and, as used herein 
means a non-steroidal anti-inflammatory agent ("NAISD") having 
anti-inflammatory and anti-pyretic activity and which inhibit 
prostaglandin synthesis. 
Such agents include salicyclic acid, sodium salicylate, phenylbutazone, 
oxyphenbutazone, antipyrine, dipyrone, mefenamic acid, flufenamic acid, 
ibuprofen, flurbiprofen, fenoprofen, ketoprofen, naproxen, diclofenac, 
ketoprofen, tolmetin, naproxen, sulindac, phenylbutazone, 
oxyphenylbutazone, diflusinal, piroxicam, meclofenac and the like. Aspirin 
and aspirin-type anti-inflammatory agents are known inhibitors of various 
enzymes, particularly prostaglandin synthetase, enhance or potentiate the 
action of narcotic analgesics, and such drugs have been used in such 
combinations of ingredients as: codeine and aspirin and Darvon and 
aspirin. 
Thus, it is an object of the invention disclosed and claimed herein to 
provide a new combination of analgesic agents in which the analgesic 
effect of the substances of the combination will be greatly potentiated 
over the analgesic effect attained when each substance is considered 
separately, thereby achieving a synergistic effect approaching the 
analagesic efficacy of morphine. 
Potentiation is achieved with sub-therapeutic dosages of aspirin and 
aspirin-type anti-inflammatory, anti-pyretic agents, thereby reducing the 
side effects normally experienced with these agents.

Further objects and advantages will become apparent to one skilled in the 
art as the description of the invention proceeds. 
The results of the acute tests, or experiments, are reflected in Tables 1 
and 2 set out hereinafter in section "A". The chronic tests and 
experiments are described in section "B" hereinafter. The results of acute 
tests, or experiments, using a combination of substances is reflected in 
Table 3 of section "C" set out hereinafter. 
D-phenylalanine in pure form, or as part of DL-phenylalanine has been 
administered to numerous patients suffering from both acute and chronic 
pain. Analgesia has been obtained in at least (60%) of the subjects. 
A. General Description of Acute Tests of Individual Substances and Effect 
of Substances Tested 
The tests herein described were intended to establish the analgesic 
activity of the analgesic agents and compositions containing those agents, 
disclosed herein, and to establish at least one safe and practical method 
of securing in an animal species, such as mammals, a long lasting, or 
prolonged, analgesic effect. 
One test for the ability of the animal to withstand pain is the hot-plate 
test. It is a traditional pharmacological screening procedure in which 
drug-treated mice are placed on a hot plate and the analgesic effect of 
the drug is measured by now soon a mouse jumps off the hot plate. In the 
specific hot-plate test described herein the temperature of the plate was 
maintained at 55.degree. C. 
Another test for the ability of the animal to withstand pain is the 
phenylquinone writhing test. Phenylquinone, when injected into mammals 
such as mice, causes intense pain manifested by stretching, pelvic 
twisting, and extension of hind legs. An analgesic such as morphine when 
administered to the mouse, will either abolish or reduce the number of 
such reactions to phenylquinone, the totality of response being known as 
writhing. 
The practical method of administering the analgesic agents and compositions 
herein described in mice was by intraperitoneal injection. The dosage 
injected was 250 mg/kg, the dosage being proportional to the weight of the 
mouse treated. 
The "control" for the hot-plate test was determined by placing an untreated 
mouse on a metal hot plate maintained at 55.degree. C. The time it takes 
the untreated or "control" mouse to jump, after being placed on the hot 
plate, is noted. After being treated by an intraperitoneal injection of 
drug, the test mouse is again placed on the hot plate, and the laspe of 
time until the animal jumps is noted. This test of a treated mouse is 
repeated at various specified times. Specifically, the mouse is tested 
after a single injection for 2 hours at 30 minute intervals. In the 
experiments with mice, six to twelve mice were tested with each dose of 
injected substance. A "highly significant" analgesic effect will be 
demonstrated by a time lapse, before the mouse jumps, constituting an 
increase of several-fold (3 or 4) over that of the control. 
In the writhing test, the analgesic injected is administered to certain 
mice approximately one hour before injecting the phenylquinone. Other 
animals serving as a "control" are injected with saline solution 
approximately one hour before injecting the phenylquinone. The percent of 
animals writhing, together with the number of writhes is noted over a 
period of 10 minutes following injection of the phenylquinone. 
The human studies noted herein were carried out on more than 47 subjects 
experiencing acute and chronic pain which had not been relieved by 
conventional treatment with drugs or other procedures such as acupuncture, 
transcutaneous nerve stimulation, or laminectomy. D-phenylalanine plus 
aspirin, D-phenylalanine alone, or DL-phenylalanine were administered 
orally and the degree of relief from pain was monitored for a period of 
several weeks. 
The results of all tests were subjected to statistical analysis to 
determine the degree of significance of results. 
EFFECT OF THE SUBSTANCES TESTED 
D-phenylalanine and hydrocinnamic acid both exhibited highly significant 
analgesia by the hot-plate test. This conclusion is supported by the data 
shown in Table I. With injection of a saline solution, as a control, no 
significant increase in jump time was observed or noted. With injection of 
D-phenylalanine or hydrocinnamic acid, a highly significant increase in 
time lapse before jump was observed. 
TABLE 1 
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Analgesic Potency As Determined by the Hot Plate Method 
Treatment (Injection) 
% Increase in Jumping Time 
______________________________________ 
Saline 30%** 
D-phenylalanine 
300%* 
L-phenylalanine 
30%** 
Hydrocinnamic acid 
300%* 
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*Highly significant 
**Not significant 
Specificity of D-phenylalanine as an analgesic agent substance was is 
determined by comparison of results from its injection with results from 
injection of L-phenylalanine, a naturally occurring amino acid, whose 
testing showed minimal, if any, significant analgesic potency. Naloxone 
exhibits the ability to reverse analgesia produced by D-phenylalanine. 
Table 2 shows that injection of D-phenylalanine also significantly 
decreased the number of test animals showing writhing. Reduction in 
intensity of writhing is shown by the reduction in number of writhes per 
minute. Table 2 again shows that injection of L-phenlalanine has 
relatively little effect. 
TABLE 2 
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Analgesic Potency of D-Phenylalanine As Determined 
by the Phenylquinone Writhing Test 
No. of Writhes/ 
Treatment (Injection) 
% Writhing 
Minute 
______________________________________ 
Saline 90% 5.4 
D-Phenylalanine 60% 2.5* 
L-Phenylalanine 80% 4.4** 
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*Highly significant 
**Not significant 
Results using D-leucine in the hot plate and writhing tests are shown in 
the following Table 3. Just as in the case of D-phenylalanine, analgesia 
by D-leucine was reversed by naloxone. Results are also shown for the 
combination of D-phenylalanine and D-leucine in these tests. Such results 
show the potentiation of action by the combination of these amino acids. 
TABLE 3 
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Analgesic Potency of D-Leucine and D-Leucine 
Plus D-Phenylalanine as Determined by the Hot 
Plate and Phenylquinone Writhing Tests 
Hot Plate Writhing Test 
% Increase in 
# of Writhes 
Treatment (Injection) 
Jump Time per minute 
______________________________________ 
Saline -- 5.6 
D-leucine, 250 mg/kg 
300* 3.0* 
D-leucine, 125 mg/kg + 
300* D-leucine, 
D-phenylalanine, 125 mg/kg 
250 mg/kg+ -- 1.0* 
D-phenylanine, 250 mg/kg 
______________________________________ 
*Highly significant 
B. Chronic Experiments 
D-phenylalanine was injected intraperitoneally twice daily for nine (9) 
days, into mice, in an amount per injection of 250 mg per kg of body 
weight of the mouse. All animals were tested by the hot-plate test on the 
ninth day for appearance of analgesia, both before the injection of the 
phenylalanine as well as afterwards. Two types of controls were also run. 
One control group of mice was injected with saline solution; the other 
group was injected with L-phenylalanine. Twenty animals were used for each 
of these groups. 
After administration of the second dose of phenylalanine on the ninth day, 
the animals that had been injected with D-phenylalanine were injected with 
naloxone, 15 mg/kg. Naloxone is an antagonist of morphine and the 
endorphins. The purpose of this latter test was to test for withdrawal 
symptoms, because with opiate-dependent animals, the amount of injected 
naloxone will produce severe withdrawal symptoms including diarrhea, large 
weight loss, and jumping. 
The following results were observed in the mice that had been injected with 
D-phenylalanine for nine (9) days. 
(a) Tolerance to the analgesic effects did not develop. In other words, the 
degree of analgesia in the D-phenylalanine injected mice, as measured by 
the hot-plate test, on the ninth day was significantly greater than that 
observed on the first day. If morphine, or other opiate substance, had 
been administered in a similar fashion, by the ninth day the 
administration of morphine, in the same amount as administered on the 
first day would have had very little analgesic effect, the latter result 
being a reflection of tolerance. 
(b) There seems to be a cumulative effect from the repeated injections, 
over an extended period of time, of D-phenylalanine (i.e., excellent 
analgesia to the hot plate test was observed in the mice as long as 12 
hours after the last dose had been injected. 
(c) The control group of mice injected with saline solution or with 
L-phenylalanine exhibited virtually no analgesia. 
The following results were observed, after naloxane injection, in mice that 
had been injected with D-phenylalanine for nine (9) days: 
(d) No sign of addiction was observed from administration of the naloxone 
test: (i,e, there was no diarrhea, weight loss, jumping, etc.); 
(e) Naloxone only abolished the analgesia. 
The foregoing results from several tests demonstrate the efficacy of 
D-phenylalanine and D-leucine as analgesic agents. The substances are 
effective, do not produce tolerance or dependence, and are extremely safe. 
Even at very high doses of D-phenylalanine (DPA) given over an extended 
period of time (1 gm/kg/day for 30 days) no deaths or tissue pathology 
were observed in any of the experimental animals. 
The degree of analgesia obtained with D-phenylalanine is not, initially, as 
intense as that secured by use of morphine and other narcotic analgesics. 
It is considered that the analgesia produced by the combination of 
D-phenylalanine and D-leucine is equivalent to that obtained with fairly 
large doses of morphine (15 to 20 mg/kg). 
C. Potentiation of Analgesia With Anti-inflammatory, Anti-pyretic Agents 
It has been discovered that the analgesia produced by D-phenylalanine, 
D-leucine, DL-phenylalanine, DL-leucine and hydrocinnamic acid can be 
greatly enhanced, or potentiated, by having a drug having 
anti-inflammatory and anti-pyretic activity combined therewith. Such 
anti-inflammatory agents include aspirin and the aspirin-type 
non-steroidal anti-inflammatory agents (NAISDs). The NAISDs are well known 
and fall within seven major classes (1) propionic acid derivatives, (2) 
indole derivatives, (3) fenamates, (4) pyrrolealkanoic acids, (5) 
pryazolone derivatives, (6) oxicams, and (7) salicylic acids. The NAISDs 
are similar in mechanism to that of aspirin and are mediated chiefly 
through inhibition of the biosynthesis of prostaglandins. 
The protype of the non-steroidal anti-inflammatory agents is aspirin, and 
the other anti-inflammatory agents are often referred to as aspirin-type 
or aspirin-like drugs. (See Goodman and Gilman, The Pharmacological Basis 
of Therapeutics, Sixth Edition, p. 682 (MacMillan Publishing Co., Inc., 
1983). These agents include indomethacin(Indocin), diclofenac sodium, 
ibuprofen (Motrin, Rufen, Advil and Nupren), tolmetin sodium (Tolectin), 
naproxen (Naprosyn, Anaprox), fenoprofen(Nalfon), sulindac (Clinoril), 
meclofenamate (Meclomen), mefanimic acid (Ponstel), flurbiprofen, 
phenylbutazone, oxyphenbutazone, antipyrene, dipryone, flunamic acid, 
ketoprofen, piroxicam (Feldene), diflusinal (Dolobid), and the like. 
Any non-steroidal anti-inflammatory agent (aspirin or any aspirin-type 
anti-pyretic, anti-inflammatory agent) may be used in the practice of the 
present invention disclosed and claimed herein. 
Significantly, the hot-plate test reflects that injection of, for example 
aspirin, indomethacin or diclofenac sodium at a dose which failed to 
provide a significant increase in jumping time of a mouse, when combined 
with an analegisic agent employed in the practice of this invention, i.e., 
D-phenylalanine, provided an unusually highly effective analgesia as is 
reflected in Table 4. Prior to the invention herein, it could not have 
been predicted that such a combination would produce such an unusual and 
unexpected effect. In fact, the analgesia obtained by use of the 
combination of substances approached the analgesia obtained by one of the 
most potent known analgesics, morphine. 
For combination experiments involving D-phenylalanine and representative 
aspirin-type anti-pyretic, anti-inflammatory agents, the following 
procedure was used: A series of mice were first administered either 
indomethacin or diclofenac sodium. At various times, the animals were 
tested by the hot plate method. After one hour, D-phenylalanine was 
administered at a dose of 250 mg/kg and the animals were tested for 
analgesia for another two hours. The results are shown in Table 4. When 
D-phenylalanine was administered to mice which had previously been treated 
with an aspirin-type anti-pyretic, anti-inflammatory agent, the effect of 
the combination was to increase the jumping time 1100 or 1200%, i.e., 
eleven or twelve-fold. In some instances, the increase was at the maximum 
equivalent to that of morphine or other narcotic analgesics. It will be 
recalled from Table 1 above that the same dose of D-phenylalanine caused 
an increase in jumping time of only 300%, while as shown in Table 4 that 
of the representative aspirin-type anti-pyretic, anti-inflammatory agents 
gave essentially non analgesia as measured by the hot plate test. Thus, 
the results from the combination of the two substances represent a true 
synergism, or example of drug potentiation. 
TABLE 4 
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Analgesic Potency of Combinations of 
D-phenylalanine and Indomethacin or Diclofenac Sodium 
% Increase 
Treatment in Jumping Time 
______________________________________ 
D-phenylalanine, 250 mg/kg 
300 
Indomethacin, 20 mg/kg 
0 
Indomethacin, 20 mg/kg followed by 
1100* 
D-phenylalanine, 250 mg/kg 
Diclofenac sodium, 40 mg/kg 
33 
Diclofenac sodium, 40 mg/kg followed by 
1200* 
D-phenylalanine, 250 mg/kg 
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*Highly significant potentiation 
Preliminary experiments in treatment of pain in human subjects using 
D-phenylalanine plus aspirin, or DL-phenylalanine, administered orally, 
shows that the efficacy of these substances as analgesics in man has been 
confirmed. As shown in Table 5 which lists representative results, long 
lasting pain relief can be achieved with any of the above mentioned 
chemicals, including combinations of D-phenylalanine, DL-phenylalanine, 
D-leucine, DL-leucine and hydrocinnamic acid aspirin-type anti-pyretic, 
anti-inflammatory agents given for three or four days. No side effects, 
tolerance or signs of addiction were observed in any patient. 
Preliminary success in experiments in treatment of pain in human subjects 
was also achieved using D-leucine. 
TABLE 5 
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D-Phenylalanine (DPA) Analgesia In Humans 
Time 
Condition 
Duration Prior Treatmt. 
on DPA Result 
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Whiplash 
2 years Empirin, 3 days Complete 
Valium relief, 
1 month 
Osteo- 5 years Empirin + Main- Excellent 
arthritis, aspirin tained relief, 
fingers, relief, joint 
thumbs of stiffness 
both hands reduced 
Rheumatoid 
Several Empirin + 1 week Consider- 
arthritis 
years codeine able relief 
left knee, 
Osteo- 
arthritis 
of hands 
Low back 
Several Spinal fusion, 
3 days Much less 
pain, neck 
years percutaneous pain 
pain nerve stimula- 
tion 
Low back 
Several 90 acupunct- 3 days Back pain 
pain years ures gone, 
walked 
one mile 
Low back 
Several Laminectomies, 
3 days Good to 
pain years Depomedrol, excellent 
percutaneous relief 
nerve stimula- 
tion 
Fibrositis 
* Empirin 2 days Pain gone, 
of muscle recurred 
after 
2 days 
Migraine 
Several * 2 days Good relief, 
years may 
prevent 
recurrence 
Cervical 
* * 2 days Very little 
osteo- pain 
arthritis 
plus post- 
operative 
pain 
Severe Several Empirin 3 days Excellent 
lower back 
years Valium relief 
pain (Inter- 
mitent) 
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*Means information not available 
In the treatment of pain in human subjects, reported in Table 5, the dosage 
of D-phenylalanine administered was in the range of 800-1,000 mg per day, 
administered in 4 equal dosages of 200-250 mg per dose. These amounts had 
been selected conservatively. When administration was with aspirin, 300 mg 
of aspirin was added to the D-phenylalanine. When DL-phenylalanine was 
administered, the dosages were doubled to 400-500 mg per dose, since the 
D-phenylalanine component of the DL-phenylalanine was 50%. In all cases 
where the DL form of phenylalanine or leucine is employed, the dosage of 
the D-form is doubled. 
The preferred dosage range for D-phenylalanine is 400-3,000 mg per day, 
preferably taken in four divided dosages of from 100-750 mg per dose. When 
the preferred dosage range is administered with aspirin, the aspirin 
component will range from 125 to 950 mg per dosage. Three hundred mg per 
dose is preferred. 
Aspirin and the aspirin-type anti-pyretic, anti-inflammatory agents are 
employed in amounts of from one-forth their normal therapeutic dose, to 
and including their therapeutic dosages, depending upon patient response. 
Generally speaking, potentiation is achieved with sub-therapeutic dosages, 
however, in cases where an immediate response is not achieved, the dosage 
of aspirin, or an aspirin-type drug may be increased in combination with, 
for example DPA, until analgesia is obtained, and then lowered. 
The therapeutically effective amounts or dosages of the aspirin-type drugs 
useful in the practice of this invention are set forth, in for example, 
the Physician's Desk Reference and may be used as a pharmaceutically 
acceptable salt. 
It has also been determined by experimentation with animals that 
D-phenylalanine itself exhibits anti-inflammatory activity. The 
anti-inflammatory activity of D-phenylalanine was determined as follows: 
RAT PAW CARRAGEENAN TEST FOR ANTI-INFLAMMATORY ACTION OF D-PHENYLALANINE 
The rat paw carageenan test is a standard test for determining whether a 
drug can act as an anti-inflammatory agent in man. Carageenan is a highly 
irritating substance and cases swelling of tissues when injected. An anti 
inflammatory agent is one which can counteract such swelling. A convenient 
tissue for accurately measuring the degree of swelling is the hind paw of 
the rat which swells up greatly when the carageenan is injected. The 
degree of swelling is easily measured by immersing the paw in water and 
noting the degree of fluid displacement. In the experiments carried out, 
DPA was administered either orally or intraperitoneally 2-3 hours before 
the carageenan. The effect of DPA was compared with that of control paws 
of animals administered saline instead of DPA. 
TABLE 6 
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Activity of D-Phenyalanine in Rat Paw Carageenan Test 
DPA Time Before 
% Inhibition 
(mg/kg) Route Carageenan 
Swelling 
______________________________________ 
1000 i.p. 120 -71 
500 i.p. 120 -59 
250 i.p. 120 -61 
125 i.p. 120 -61 
1000 oral 180 -30 
500 oral 180 -42 
250 oral 180 -35 
125 oral 180 -38 
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In view of the results obtained by experimentation with D-phenylalanine, 
D-leucine, DL-phenylalanine, DL-leucine and hydrocinnamic acid, and 
mixtures thereof, alone, and in combination with aspirin and other 
aspirin-type or aspirin-like non-steroidal anti-pyretic, anti-inflammatory 
agents, the latter yielding synergistic effect, the present invention 
provides methods and compositions for treating pain and inflammation in 
mammals including humans. The combination therapy is particularly suited 
to patients who initially do not respond to treatment with 
D-phenylalanine, D-leucine, DL-phenylalanine, DL-leucine or hydrocinnamic 
alone. 
The compositions of the present invention are preferably solid oral unit 
dosage forms comprising a therapeutically effective amount of an analgesic 
agent selected from the group consisting of D-phenylalanine, 
DL-phenylalanine, D-leucine, DL-leucine and hydrocinnamic acid, in 
combination with each other or aspirin or an aspirin-type anti-pyretic, 
anti-inflammatory agent. The compositions may additionally comprise 
binders, fillers, lubricants, colorants, and the like, and are prepared by 
methods well known in the art. 
The term "pharmaceutically acceptable salt", as used herein refers to the 
physiologically acceptable, nontoxic salts of the non-steroidal 
anti-inflammatory agents employed in the practice of this invention.