Back to the Top
Dear All
I would like to know the common cosolvents/surfactants with their
maximum permitted concentration that can be used in the preparation of
iv formulations for conducting preclinical studies in small animals
(rodents) and large animals (non-rodents) .
Thanks in advance
Naveen Sharma
Back to the Top
Naveen,
here are some information I can provide you with:
for rodents:
Polysorbate 80 1 to 2 g/kg max
Solutol HS15 around 1 g/kg max
DMSO 4 to 5 mg/kg
PEG400 7 g/kg
N-methylpyrrolidone 200 mg/kg
For non-rodents:
no PS80 in dogs
Solutol HS15 25 mg/kg in dogs
DMSO 2 mg/kg in dogs
I would suggest that you first use surfactants if you perform PK
studies. In
this case you should also consider the CMC of each surfactant and
prefer to
work with concentrations up to 10% of the CMC. This would not increase
dramatically the compound's solubility but this will minimize the risk
of
precipitation and/or default in the release of the active.
Does it make sense ?
Regards,
Frederic
Back to the Top
Dear Frederic,
Poor aqueous solubility of NCE's is difficulty faced by all of us
preformulations/formulation development scientists. This problem
becomes more accute when evaluating preclinical safety of the drug in
animals. 'Developability' should be a main criteria for lead
identification.
Coming to solvents/surfactants, what is your opinion Cremophor EL, RH
40, Pluronics? PVP is also useful in many cases but I am not too sure
about the levels to use. Perhaps you can throw some light on this.
You have mentioned DMSO. But as it is never used in human formulations,
what would the stand of regulatory authorities on this.
Regards,
Sunil V
Lupin Research Park,
Back to the Top
Dear Naveen,
The search for an appropriate solvent for preclinical studies continues
and would go on !!!!.
There is nothing like dissolving a test compound (TC) in distilled
water and start working immediately. Half of your problems are solved.
But that does not happen always. I have seen various Scientists using
different approaches and in our Lab - we have tried using
CYCLODEXTRIN and let me tell you it was not easy - lots of things we
had to address like concentration to be used,
making a suspension or a clear solution, assessing the effect of
cyclodextrin on oral bioavailability etc. etc.
But finally we could achieve satisfactory results. So, you could try
cyclodextrin also in addition to the solvents others have
recommended.
I came across the following suggestions once which I am reproducing for
you to read :
A.) For in vitro studies/ and in vivo-i.v. injection (for a clear
solution):
1. Solubilize in as low quantity of DMSO as possible. Serial dilutions
are made in appropriate assay buffer. TC (Test compound) may
precipitate if the conc of
DMSO decreases. In my experience, DMSO has nonspecific effect including
radioligand binding and enzyme assays. Use solvent control.
2. PEG 200 or 400. Make serial dilutions in assay buffer.
3. Dissolve in ethyl alcohol. Further dilutions are made in assay
buffer or saline.
4. Acid phosphate buffer: 0.1M NaH2PO4 and HCl to pH 2.6 to 2.9 (for
iv studies).
5. Dissolve in 5% Na2CO3 or saturated bicarbonate, dilute with saline
1:49, v/v or adjust pH with HCl.
6. Solution of TC with stoichiometrically (assuming that you know the
charge on the TC that reacts with the charge on the solvent) equivalent
amounts of KOH or L-arginine (thereby creating the K or arginine salt
of the TC).
7. 0.1N NaOH and saline
8. 25% ethyl alcohol (95%), 25% PEG (5%) and 50% saline
9. TC may be complexed with 1.8% w/v hydroxypropyl-beta-cyclodextrin
and dissolved in 1M NaOH. Adjust the pH with 1M HCl to acidic side.
B.) For in vivo studies: prepared as a suspension and administered
orally by gavage
1. 0.5% w/v methyl or hydroxyethyl cellulose
2. 0.5% w/v hydroxypropyl methyl cellulose in 0.1% w/v aqueous
polysorbate (Tween 80)
3. 0.5% to 1% w/v CMC or SCMC and 0.08 to 0.5% Tween 80
4. 5-10% gum arabic
Good luck!
Y.Chugh Ph.D
Back to the Top
Sunil,
I fully agree with your first point. As preformulation/formulation
scientists we have to face this key issue of lack of solubility. But
that is
our job to convince research project teams and chemists that solubility
is a
key point if we want NCEs to be effective in a reproducible way. The
result
should be the implementation of the solubility as a cut-off in the lead
nomination.
Coming back to surfactants and cosolvents in preclinical safety I would
give
up with the DMSO.
Cremophor EL is a good candidate for drug solubilization with a DL50 of
2.5
g/kg for mice and 0.64 g/kg in dogs (Handbook of pharmaceutical
excipients).
I am not really happy with the use of Pluronics but PVP should be used
as it
is a common ingredient for human use.
Did you consider the use of cyclodextrins ?
Regards,
Frederic
Back to the Top
Dear Dr. Chugh,
Could you please tell us what cyclodextrin you used and the
conditions?. I am also trying to get my compound dissolved in
hydroxypropyl cyclodextrin. However, the drug remains a suspension in
30% cyclodextrin. I barely see the drug in plasma upon dosing both IV
and orally. Can the cyclodextrin-drug mixyure precipitate upon IV
dosing?
Thank you,
Chandrani Gunaratna
Chandrani Gunaratna, Ph.D.
Senior Research Scientist
Bioanalytical Systems
2701 Kent Avenue
West Lafayette, IN 47906
(765)463-4527
Back to the Top
One quick note of caution regarding PVP. It is fine for humans but
causes
histamine release in dogs. The reaction is highly variable ranging from
no
discernible effect to reddening of extremities to total collapse!. If
your
toxicology package will use dogs you should probably not use PVP.
Regards
Fiona
Fiona Stavros Ph.D.
Director PreClinical Toxicology
Texas Biotechnology Corporation
Back to the Top
Dear Frederic, Yati and Chandrani,
Cyclodextrins are good solubilisers, however no IV formulation
containing Cyclodextrins (including hydroxy propyl beta cyclodextrin)
is approved in US, although there are couple of intra articular
injections approved in Japan. Recently, however US FDA approved two
Formulations (interestingly from Pfizer, Voriconazole and Ziprasidone)
containing a sulfobutyl ether fl-cyclodextrin (Brand name Captisol), so
it may be advisable to use Captisol in place of HP beta CD.
Regards,
Sunil
Back to the Top
Dear all,
cyclodextrins (HPbCD and SBECD) can easily be used in IV at
concentrations
up to 30%.
But I would not suggest their use PO due to issues of the kinetics of
decomplexation. The cyclodextrin tends to solubilize the most lipophilic
compounds. Such compounds will have low (at least slow) release in the
GI
tract because of their affinity for cyclodextrins. Then absorption will
be
limited by the drug release kinetics from cyclodextrin.
Per IV we consider that the use of cyclodextrin is much more
comfortable due
to dilution of a small injection volume in a larger plasma volume. But
we
always perform preformulation studies to define a complexation constant
that
characterizes the affinity for the drug-cyclodextrin interactions. If
complexation constants are too high we do not use this formulation.
Last point. I don't expect any precipitation in the plasma if your
formulation contains cyclodextrins in pH7.4 buffer. Then there is no
reason
for the drug to precipitate as the release from the complex will be
conducted by the ratio between its affinity for the cyclodextrin and its
plasma max solubility.
Regards,
Frederic
Pfizer Global R&D
Back to the Top
Another thought is an emulsion. It has been done before with Diazemuls
for
example. I know they can be unstable and are probably tricky things to
store
and transport as a marketed product, but if they avoid the possibility
of
toxic solvents perhaps they might be used more. Does anyone have
experience
of them?
Andrew Sutton
Guildford Clinical Pharmacology Ltd.
Unit 33, The Surrey Technology Centre
Guildford, Surrey GU2 7YG, UK
Back to the Top
Cremophor also releases histamine in dogs, like PVP. It was associated
with
dramatic anaphylactic reactions in patients given iv anaesthetics back
in
the 1970's, namely: Propanidid and the steroidal anaesthetic, Althesin.
I
was told that Cremophor is a huge and somewhat variable mixture of
surfactant molecules very difficult to identify and probably varying
from
batch to batch, so although it might work out in early animal
experiments
one has to wonder if it is wise to choose a solvent so poorly suited to
the
eventual clinical pharmaceutical formulation.
Andrew Sutton
Guildford Clinical Pharmacology Ltd.
Unit 33, The Surrey Technology Centre
Guildford, Surrey GU2 7YG, UK
Back to the Top
Naveen,
The Humane Scoiety of United States had Dr. David Smith
presented "Dosing and Limited Volume; an European View" which
addressed many preclinical questions such as formulation.
http://www.hsus.org/ace/Article_Printer_Friendly?Content_ID=11444
Bill Tong
Memorial Sloan Kettering Cancer Center
Back to the Top
Dear Sunil,
You are right when you talk about the use of cyclodextrin in I.V.
formulations.
As a Preclinical Biologist I think a bit different. My aim at an early
Preclinical stage is to give the best chance to our compounds to
ACT/PERFORM - whichever the way be ?? . We do not want our molecules to
get killed because US does not have any formulation using cyclodextrin
- Of
course I am not advocating the blind use of cyclodextrin !!!!! because I
have encountered the difficulties with it's use.
Early preclinical studies (in my personal opinion) do not require a
formulation approach and if the molecules are given a fair chance to
show
the efficacy by any means ( of course some sensible) - we can than
approach
our formulation guys. That's infact we do at our group.
Our group has extensively worked with some highly insoluble compounds
and
we have weathered many a storms to save them from being discarded. And
during those studies only we had started using cyclodextrin and YES we
did
plenty of comparative studies using different suspensions of CMC,
Tween, pH
adjustments etc. etc...
I completely agree with Frederic that complexation and decomplexation
issues with cyclodextrin remains an issue and we have to pretty cautious
before making any conclusions.
Though again we have come across compounds like say Linezolid - has a
poor
solubility and we have tried to establish it's PK profile in our lab in
various species of animals and we have tried - cyclodextrin, CMC, Tween
and
just plain water suspension. Everything works and gives the similar
efficacy and PK profile. So, the characteristics of the compound also
plays
a vital role.
I would only advocate the concept that - Give your molecules a fair
chance
to work and use a balanced approach and try to achieve the proof of
concept with your compounds.
Y.Chugh Ph.D
Back to the Top
Dear dr Chugh,
I mostly agree with your points. As a biologist you should want to have
the
drug substance in the animal model whatever the formulation and/or
dosing
route is.
My view is really to adapt the formulation to the type of study. We
have the
habit to work on "proof of concept" formulations (we also call them
"exotic") for studies where the aim is to show that if the drug is in
the
animal model then there is an effect.
But for some studies (PK for instance) I don't suggest to use this kind
of
formulation because you should then conclude on effects that are more
formulation dependent than due to the compound. If you have the "real"
compound PK profile then you should always find a formulation scientist
to
suggest some work to optimize compound properties with some work on
formulation.
It is much easier to try and enhance poor properties with some
formulation
work than to try and reach properties that were artificially nice in
preclinical studies.
For clinical studies it is obvious that Sunil should use relevant
(known as
"for human use") excipients. But for preclinical studies if you also
test
the unloaded vehicle then you should be able to prove that the vehicle
does
not interfere with the drug and therefore that data is only due to the
drug.
Last point about cyclodextrin complexation: the trouble with this
excipient
is that you can calculate a complexation constant but it is quite
difficult
to define the value beyond which you should avoid its use in a
formulation.
In the case of Linezolid it seems that complexation with cyclodextrin
is not
high enough to interfere with PK parameters.
Regards,
Frederic DOC
PFIZER Global R&D
Fresnes Laboratories
FRANCE
Back to the Top
I would like to receive comments/obseravtion regarding the use of
PEG400 in
oral dose formulations. Thanks in advance. Ed O'Connor
Back to the Top
Dear Ed,
the same as previously said with other cosolvents and surfactants can be
said for PEG400. If you need a good solubilizer for your compound why
not
try this agent. It really depends on the role you want your formulation
to
play in absorption.
For early preclinical studies (or proof of concept) it can be used. But
if
you need a formulation relevant to future human dosage forms you should
avoid this vehicle.
How does PEG400 act ? PEG400 will dramatically increase the solubility
of
your active. If it is high enough (much more than water solubility at
each
pH) what will happen when you dose PO ? A part (potentially large) is
supposed to precipitate in an amorphous state in the GI before being
solubilized and absorbed.
That is why I would not suggest to use this vehicle if you want to
assess
the impact of particle size and shape of your active on its dissolution
in
the GI tract (and therefore on absorption). How would you then be able
to
recommend a polymorh or another for the chemical synthesis ?
Furthermore the PEG400 is sometimes not well tolerated by animals if you
need to dose large volumes.
Does it make sense ?
Regards,
Frederic
Pfizer Global R&D
Fresnes Laboratories
FRANCE
Back to the Top
Thanks Frederic. That is what I would guess would happen since the test
article precipitates out of solution when acid is added. Suspensions in
methyl celluloses fall out of suspension rapidly-in the dose range we
need.
COrn oil appears to give the best lifetime in suspension.
PharmPK Discussion List Archive Index page
Copyright 1995-2010 David W. A. Bourne (david@boomer.org)