What is the half-life of inosine in the blood?

Looked but could not find. Check out http://www.isoprinosine.com/ippppharmasub.html
The table cell where the half life of inosine should be listed is blank!

-shiva777

Hi, svdh-ga:

You might be interested in this study:

http://nsr.bioeng.washington.edu/Research/D.III.pdf

Inosine, a metabolite of adenosine, was measured in concentrations
over time in cardiac epithelial capillaries of guinea pig hearts,
following cathetered introduction of adenosine.  Experimental results
showing falling concentrations are graphed on page 38.

Subject to my error in interpreting the graph a ballpark halflife of
10 secs. appears reasonably accurate.  As discussed earlier in the
article, inosine can be dephosphorylated into uric acid, through the
actions of known enzymes.  The rate of decay appears somewhat
dependent on concentration (with high concentrations producing more
rapid decay).

If you are looking for more definitive measurements, eg. in human
subjects, in arterial blood, etc., please clarify your question.  The
state of the art on this would probably require a trip to a research
hospital library.

regards, mathtalk-ga

There appear to have been three human studies of inosine, in 1990,
1996, 1999. I'll try to track them down to see if they contain a
definitive answer. There was another study that purported to show some
performance enchancement in muscle builders, but no data were given to
support the claim. In the meantime, the graph in this report seems to
indicate a rapid metabolization.

Inosinic acid and its metabolites
http://imtakt.com/TecInfo/TI047E.pdf

hlabadie-ga

Here are the three human studies. None are online. The abstracts
themselves don't answer the question.


1: Med Sci Sports Exerc  1996 Sep;28(9):1193-8 

Effect of inosine supplementation on aerobic and anaerobic cycling
performance.

Starling RD, Trappe TA, Short KR, Sheffield-Moore M, Jozsi AC, Fink
WJ, Costill
DL.

Human Performance Laboratory, Ball State University, Muncie, IN 47306,
USA.

Ten competitive male cyclists completed a Wingate Bike Test (WIN), a
30-min self-paced cycling performance bout (END), and a constant load,
supramaximal cycling spring (SPN) to fatigue following 5 d of oral
supplementation (5,000 mg.day-1) with inosine and placebo. Blood
samples were obtained prior to and following both supplementation
periods, and following each cycling test. Uric acid concentration was
higher (P < 0.05) following supplementation with inosine versus
placebo, but 2,3-DPG concentration was not changed. The data from WIN
demonstrate that there were no significant differences in peak power
(8.5 +/- 0.3 vs 8.4 +/- 0.3 W.kg body mass-1), end power (7.0 +/- 0.3
vs 6.9 +/- 0.2 W.kg body mass-1), fatigue index (18 +/- 2 vs 18 +/-
2%), total work completed (0.45 +/- 0.02 vs 0.45 +/- 0.02 kJ.kg body
mass-1.30-s-1), and post-test lactate (12.2 +/- 0.5 vs 12.9 +/- 0.6
mmol.l-1) between the inosine and placebo trials, respectively. No
difference was present in the total amount of work completed (6.1 +/-
0.3 vs 6.0 +/- 0.3 kJ.kg body mass-1) or post-test lactate (8.4 +/-
1.0 vs 9.9 +/- 1.3 mmol.l-1) during END between the inosine and
placebo trials, respectively. Time to fatigue was longer (P < 0.05)
during SPN for the placebo (109.7 +/- 5.6 s) versus the inosine (99.7
+/- 6.9 s) trial, but post-test lactate (14.8 +/- 0.7 vs 14.6 +/- 0.8
mmol.l-1) was not different between the treatments, respectively.
These findings demonstrate that prolonged inosine supplementation does
not appear to improve aerobic performance and short-term power
production during cycling and may actually have an ergolytic effect
under some test conditions.

Publication Types:
    Clinical Trial
    Randomized Controlled Trial

PMID: 8883009 [PubMed - indexed for MEDLINE]



2: Med Sci Sports Exerc  1990 Aug;22(4):517-22 

Effect of inosine supplementation on 3-mile treadmill run performance
and VO2
peak.

Williams MH, Kreider RB, Hunter DW, Somma CT, Shall LM, Woodhouse ML,
Rokitski
L.

Department of Health, Physical Education and Recreation, College of
Education,
Old Dominion University, Norfolk, VA 23529-0196.

The purpose of this study was to investigate the ergogenic effect of
oral
inosine (IN) supplementation (6,000 mg.d-1 for 2 d) upon 3-mile run
time (3MTIME) and VO2 peak. Nine highly trained endurance runners
participated in a double-blind, placebo (PL), crossover study. Each
subject undertook an IN or PL trial, consisting of three exercise
tests: a submaximal warm-up run (SUBRUN), a competitive 3-mile
treadmill run (3MRUN), and a maximal treadmill run (MAXRUN) to
determine VO2 peak and time to exhaustion (MAXTIME). Additional
measurements during the 3MRUN and MAXRUN included oxygen uptake (VO2),
ventilation (VE), respiratory exchange ratio (R), and ratings of
perceived exertion (RPE); blood samples were also taken prior (PRERUN)
to the SUBRUN test and following the SUBRUN, 3MRUN, and MAXRUN tests
in order to assess glucose, pyruvate, lactate, phosphorus, 2,3-DPG,
hemoglobin, and uric acid. Analyses of the data revealed no
significant effect of oral IN supplementation either upon 3MTIME (IN =
18.31 +/- 1.21; PL = 18.33 +/- 1.15 min) or VO2 peak (IN = 58.6 +/-
5.1; PL = 60.7 +/- 4.5 ml O2.kg-1.min-1) or upon other dependent
variables. MAXTIME was significantly longer during the PL trial (P
less than 0.05), suggestive of a possible impairment effect of oral IN
supplementation. Based upon our data, we conclude that IN is not an
effective ergogenic aid to enhance athletic performance of an aerobic
nature.

Publication Types:
    Clinical Trial
    Controlled Clinical Trial

PMID: 2402214 [PubMed - indexed for MEDLINE]



1: Int J Sport Nutr  1999 Dec;9(4):333-44 

Inosine supplementation has no effect on aerobic or anaerobic cycling
performance.

McNaughton L, Dalton B, Tarr J.

Sports Science Dept., Kingston University, Kingston upon Thames,
Surrey,
England.

The two basic aims of this study were to add to the limited literature
concerning Inosine as an ergogenic aid, and to determine the effects
of Inosine supplementation over a period of 5 and 10 days, at a dosage
of 10,000 mg.d-1 on measures associated with aerobic and anaerobic
performance. Seven trained, volunteer male subjects (body mass = 63.0
+/- 8.7 kg, VO2max = 67.9 +/- 3.3 ml.kg-1.min-1) participated in this
study. The subjects completed three test sessions, each comprising
three tests (5 x 6-s sprint, 30-s sprint, and 20-min time trial).
Supplementation was carried out in a random, double-blind manner, and
the test sessions were undertaken prior to (Baseline, B), on Day 6,
and on Day 11. Blood was sampled prior to supplementation as well as
on Days 6 and 11 and was analyzed for uric acid and 2,3 DPG. An
analysis of the data indicated no performance benefit of
supplementation and no improvement in 2,3 DPG concentration. Uric acid
concentration increased significantly after both Days 6 and 11 (p <
0.03 and p < 0.004, respectively). It is concluded that Inosine has no
ergogenic effects but may cause possible health problems if taken over
long periods of time.

Publication Types:
    Clinical Trial
    Randomized Controlled Trial

PMID: 10660865 [PubMed - indexed for MEDLINE]


hlabadie-ga

http://aidsinfo.nih.gov/document/data/Drug_lib/Technical/DRUG_Tech_0016.html

Inosine is referred to as Didanosine.  Paragraph referenced with 24 in
the Pharmacology section describes the half life.

Didanosine is not a inosine.  In at least one position one of the
hydroxyl groups has been replaced by a hydrogen.  Even a seemingly
minute change like that can make an enormous difference in terms of
chemical properties such as half-life.