An efficient new cannabinoid antiemetic in pediatric oncology
Aya Abrahamov1 , Avraham Abrahamov2 and R. Mechoulam3
1 Department of Pediatrics,
Shaare Zedek Hospital, Jerusalem, Israel;
2 Department of Pediatrics, Bikur Holim Hospital, Jerusalem;
3 The Brettler Center for Medical Research, Medical Faculty,
Hebrew University, Jerusalem 91120.
Abrahamov, Aya, Avraham Abrahamov, and R. Mechoulam,
1995. An efficient new cannabinoid antiemetic in pediatric oncology. Journal of the International Hemp Association 2(2): 76-79.
Delta-8-tetrahydrocannabinol (delta-8-THC), a cannabinoid
with lower psychotropic potency than the main Cannabis
constituent, delta-9-tetrahydrocannabinol
(delta-9-THC), was administered (18 mg/m2 in edible oil, p.o.) to eight children, aged
3-13 years with various hematologic cancers, treated with different antineoplastic drugs
for up to 8 months. The total number of treatments with delta-8-THC so far is
480. The THC treatment started two hours before each antineoplastic treatment and
was continued every. 6 hrs for 24 hours. Vomiting was completely prevented.
The side effects observed were negligible.
Introduction
Cannabis preparations have been used for millenia as antiemetic drugs [1]. With the identification of
delta-9-tetra-hydrocannabinol (delta-9-THC) (Fig 1) as the psychoactive Cannabis constituent [2] its evaluation as an antivomiting agent was also made
possible. It was indeed found that delta-9-THC prevents or reduces vomiting induced
by anticancer chemotherapy [3-5]. Delta-9-THC is
marketed under the generic name Dronabinol [5].
Depending on the clinical protocol used, delta-9-THC (5-10 mg/m2 p.o.) prevents vomiting
and nausea in some patients and reduces these symptoms in others. The side effects
are those noted in marijuana users, in particular elderly ones: drowsiness, dizziness and
in rare cases anxiety. Mood changes usually predominate in younger patients.
DeIta-8-THC (Fig 1 ) is a double bond isomer of
delta-9-THC. It is less psychotropic than delta-9-THC [6],
but its antiemetic potential has not been investigated so far. In preclinical
antiemetic studies in pigeons (to be reported separately), using the methodology
previously described by us for delta-9-THC [7], we found
that delta-8-THC is at least as potent as delta-9-THC. It is much more stable than
delta-9-THC to various chemical treatments, including oxidation, and is considerably less
expensive to produce than delta-9-THC. Hence. it seemed of potential therapeutic
interest to investigate the antiemetic effect of delta-8-THC in patients. We chose
to administer delta-8-THC to children, who were expected to vomit on anticancer
chemotherapy. The reason for the age limitation was the general (but not documented)
belief that most side effects of delta-9-THC, in particular anxiety, are more prevalant in
an adult population than in a younger one. Hence delta-8-THC could possibly be
administered to children in higher doses than those given to adult patients.
We report now that delta-8-THC in an open label evaluation
was found to be an excellent pediatric antiemetic with nonsignificant side effects.
We chose an open label trial for ethical reasons. A clinical trial based on placebo
versus delta-8 THC as an antiemetic agent during anticancer treatment is
unacceptable. Our original protocol envisaged a comparison between metoclopramide
(0.3 mg/kg) and delta-8-THC (18 mg/m2). However preliminary results indicated
complete block of emesis with delta-8-THC, while metoclopramide showed variable
results. Most of the children (5 out of 8) vomited with this dose of
metoclopramide. In higher doses (0.5 mg/kg dose or above) metoclopramide caused
extrapyramidal effects. Hence for ethical reasons the protocol was modified to an
open trial design. However, we would like to point out that over a period of about
10 years, when most of the antineoplastic protocols followed in the present study were
used in our clinic, emesis was observed in about 60% of all pediatric cases even though
metoclopramide (0.3 mg/kg) was used as antiemetic agent.
Ondansetrone and other HT3-receptor blockers are today the
drugs of choice for chemotherapy-induced vomiting and nausea [8].
While such therapy is superior to previously used treatments (dopamine antagonists,
corticosteroids) adverse effects such as headache are troublesome [8] and its efficiency in delayed vomiting is
questionable. Ondansetrone is also a very expensive drug and less expensive
alternatives should be made available. Hence additional therapeutic protocols are
required.
Materials, patients and clinical protocol
Delta-8-THC was prepared
from natural cannabidiol by cyclization (Figure 1) and purified by chromatography as
previously described [9]. It was analyzed by gas
chromatography and was found to be 98% pure.
Figure 1. Chemical
structures of cannabinoid compounds
Eight children with various
blood cancers (see Table) were administered delta-8-THC (18 mg/m2 p.o.) two hours before
the start of the anticancer treatment. The drug was dissolved in corn or olive oil
(6 mg/ml), and was administered directly as oil drops on the tongue, or on a bite of
bread. The same dose was repeated every 6 hrs for 24 hrs. The treatment tor
each child is presented in the Table. Whenever additional cycles of antineoplastic
therapy were required, delta-8-THC was administered following the same time procedure
described above. Children received delta-8-THC only during days when emetogenic
drugs were administered. Established anticancer drug protocols were followed with
all patients. These are indicated below and in Table 1:
High-dose Cytarabine and Asparaginase [10] (Patient 1) MOPP-ABV protocol [11]
(Patient 2). This protocol is a standard combination of Mechlorethamine
hydrochloride, Vincristine, Procarbazine, Prednisone, Doxorubicin, Bleomycin and
Vinblastine. BFM protocol [12] (patients 3 and 8).
This protocol is a complicated standard protocol consisting of numerous antineoplastic
drugs (Vincristine, Daunorubicine, L-Asparaginase, Cyclophosphamide, Cytarabine,
Mercaptopurine, Etoposide, Methotrexate, Thioguanine) and 3 types of corticosteroids
(Prednisone, Hydrocortisone, Dexamethasone) in p.o., i.v. and intratecal
administrations. National Wilms tumor study protocol (NWTS-4) [13] (Patient 4). This protocol is a standard combination
of Vincristine, Doxorubicin, Dactinomycin. Amsacrine-high dose Cytarabine
protocol [14] (Patient 5). This is a standard
protocol consisting of Cytarabine and Amsacrine. Burkitt's lymphona protocol [15] (Patient 6). This is a standard protocol
consisting of Vinscristine, Doxorubicin Cyclophosphamide, Methotrexate and Prednisone.
Rezidive study. A.L.L. - Rez BFM 87 protocol [16]
(Patient 7). This is a standard complicated protocol consisting of numerous
antineoplastic drugs. In addition to drugs mentioned above it includes Ifosfamide
and Vindesine.
Results
The present study on
prevention of vomiting due to antineoplastic therapy took place over a 2 year period with
8 patients. Details of their antineoplastic treatment and side effects of the
antiemetic therapy are presented in Table 1. The mild side effects observed were
reported by the physician and nurse in charge. Chemotherapy protocols of the types
indicated almost invariably cause intense vomiting, which starts about 2 hrs after the
initiation of chemotherapy and gradually ends over a 24 hr period. In prelimary
trials we tried to end the antiemetic therapy after the first or second dose of the
cannabinoid, i.e. after 6 or 12 hrs. Vomiting started in most cases. Hence, in
the recorded trial, all children were given 4 doses (every 6 hours) for 24 hrs. When
the antiemetic protocol described in the "Methods, patients and clinical
protocol" section was strictIy followed, no emesis was noted during the 24 hrs of
treatment or over the next two days. In one case (patient D.E.), delta-8-THC therapy
initially was refused. The patient experienced debilitating vomiting for 24 hrs
after the antineoplastic treatment. During the second treatment cycle (which took
place after 8 days), at the patient's family request, delta-8-THC treatment was
initiated. No vomiting occurred. In a second case (A.M.), the patient refused
antiemetic treatment during a relapse of his disease as it was based on an "illicit
drug" (Cannabis). Repeated vomiting took place. Renewal of the THC
treatment, before the next administration of antineoplastic drugs, prevented additional
vomiting. As indicated in Table 1 the side effects were observed in only 2 of the 8
patients: some irritability and slight euphoria which in children is difficult to
quantify. No anxiety or hallucinogenlc effects were noted in spite of the high doses
administered.
No. | Name sex |
Age (years) |
Diagnostic treatmentc | Antineoplastic | Number and effect of antiemetic treatments |
1. | A.M. m |
10 | A.L.L.b
pre B, in relapse |
Cytarabine- L-Asparaginase |
(32), no side effects |
2. | C.O. m |
3.5 | Hodgkin's disease |
MOPP-ABV protocol |
(64), slight irritability dudng first 2 cycles |
3. | L.H. f |
4 | A.L.L., T type |
BFM protocol | (76), slight irritability and euphoria1 |
4. | M.H. f |
3 | Wilm's tumor, stage 1II |
NWTS-4 protocol |
(30), no side effects |
5. | R.M. f |
13 | A.L.L., T type in second relapse |
Cytarabine, Amsacrine protocol |
(24), no side effects |
6. | DE. m |
7 | Burkitt's lymphoma |
Burkitt's lymphoma protocol |
(114), no side effects2 |
7. | K.K. f |
6 | A.L.L. | Rez BFM 87 protocol |
(64), no side effects3 |
8. | A.A. m |
5 | A.L.L. | BFM protocol | (76), no side effects |
a Delta-8
THC, 18 mg/m2. For details see text. In all cases complete prevention of
vomiting was noted. b Acute Lymphoblastic Leukemia (A.L.L.). c see Methods, patients and clinical protocol. |
|||||
1 Metoclopromide
(0.3 mg/kg) p.o. or i.v. in previous treatment failed to prevent vomiting. 2 During first cycle, refusal to take THC caused profuse vomiting. 3 Treatment during remission after 2nd relapse and during 3rd relapse. |
Table 1. Delta-8-THC Administered to Children Treated for Various Hematologic Cancers.a
Discussion
Delta-8-THC is an isomer
of delta-9-THC, the major natural constituent of Cannabis
from which it differs only in the position of the
double bond. The stereochemistry of the two isomers is identical; their chemical
behavior is in most cases very similar [17]; their
metabolism in vivo and in vitro follow the same pathways [18].
The major chemical difference between them is that delta-9-THC is easily oxidized to the
biologically inactive cannabinol; delta-8-THC is stable, does not oxidize to cannabinol
and has a very long shelf life. Due to their close structural similarity,
delta-9-THC and delta-8-THC present essentially identical pharmacological profiles [19-21]. Quantitatively, however, delta-8-THC differs
from delta-9-THC in being about twice less potent in most, but not all pharmacological
tests.
In monkeys delta-8-THC causes a general behavior depression
in doses reported to be higher than the doses of delta-9-THC required to produce similar
effects [22, 23].
A direct comparison of the effects of delta-8-THC (20 and 40
mg total dose) and of delta-9-THC (20 mg total dose) orally administered to human
volunteers has been published [24]. The spectrum of
clinical effects was similar with both isomers, but delta-8-THC was considered to be only
3/4 as psychotropically potent as delta-9-THC. The same ratio of activity was
observed on i.v. administration.
Delta-9-THC (4 mg/kg i.m.) blocked the emetic response in
cats caused by cisplatin (7.5 mg/kg i.v.) [25]. The
metabolite 11-hydroxy-delta-9-THC, which is considerably more psychotropic than
delta-9-THC, was less antiemetic than delta-9-THC showing that, in cats at least, there is
no parallelism between the psychotropic effects and the antiemetic ones. Indeed, we
have recently shown that a non-psychotropic cannabinoid (HU-211) is more potent than
delta-9-THC as an antiemetic [7].
The LD50 values for Fischer rats treated orally with single
doses of delta-9-THC and delta-8THC, and observed for 7 days, are 1910 mg/kg and 1980
mg/kg (for males) respectively and 860 mg/kg (for females) [26].
The histopathological changes caused by these extremely high doses were essentially the
same for both delta-8-and delta-9-THC. LD50 could not be determined in either rhesus
monkeys or dogs as single oral doses of up to 9000 mg/kg of either delta-8- or delta-9-THC
in dogs or monkeys were non-lethal. Histopathological alterations did not occur in
either dogs or monkeys. A chronic oral toxicity study in rats with both isomers has
been reported. delta-8-THC was found to be slightly less toxic than the delta-9
isomer [27]. With delta-8-THC, after 119 days of
consecutive administration, no deaths were observed in males with daily doses of up to 400
mg/kg; 1/10 deaths occurred at 500 mg/kg. With females, no deaths were caused by
doses of up to 250 mg/kg; 5/13 deaths were recorded at 400 mg/kg and 12/67 were recorded
at 500 mg/kg. The above described animal and human data indicated that delta-8-THC
can be safely administered to human patients.
We found, as expected, that young children with different
hematologic cancers, who were treated with a variety of anticancer drug protocols, could
be administered doses of delta-8-THC considerably higher than the doses of delta-9-THC
generally administered to adult cancer patients without the occurrence of major side
effects, (5-10 mg/m2 of delta-9-THC generally recommended for adult patients [28] versus 18 mg/m2 of delta-8-THC used by us in
children). As mentioned above, the prevention of vomiting was complete, regardless
of the antineoplastic protocol followed . We observed no delayed nausea or
vomiting. Although the number of pediatric cancer patients treated so far is small,
the total number of treatments is considerable (480 times) as most patients underwent
several treatment cycles. Without the cannabinoid therapy we would have expected the
patients to vomit in most treatments.
In summary, the complete success in preventing vomiting due
to antineoplastic treatment in children, and the essential lack of side effects, leads us
to believe that delta-8-THC at a dose considerably higher than the doses of delta-9-THC
usually administered to adults, can serve as a new, inexpensive antiemetic agent in
pediatric cancer chemotherapy.
Reprinted by permission of the publisher from Abrahamov, Aya. Avraham Abrahamov and Raphael Mechoulam 1995. An efficient new cannabinoid antiemetic in pediatric oncology. Life Sciences 56(23/24); 2097-2102. Copyright 1995 by Elsevier Science Inc.
References