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Q: Preservatives for Drugs, Antibiotics ( Answered 5 out of 5 stars,   1 Comment )
Subject: Preservatives for Drugs, Antibiotics
Category: Science > Chemistry
Asked by: superg327-ga
List Price: $25.00
Posted: 09 Sep 2006 01:09 PDT
Expires: 09 Oct 2006 01:09 PDT
Question ID: 763594
Can you provide a list of preservatives (to maintain drug stability)
that may be used with topical antibiotics.  (eg Thimerasol).

Request for Question Clarification by welte-ga on 10 Sep 2006 12:48 PDT
How many are you looking for?


Clarification of Question by superg327-ga on 12 Sep 2006 07:04 PDT
As many as possible.  If you can include bacitracin, polymyxin,
minocycline, rifampin (or its derivatives), erythromycin, a minimum.  Thanks.
Subject: Re: Preservatives for Drugs, Antibiotics
Answered By: crabcakes-ga on 12 Sep 2006 22:44 PDT
Rated:5 out of 5 stars
Hello Superg327,

   I have compiled a ist of topical antibiotics and their preservatives:

Topical Polymyxin
Keep below 25 degrees C
Contains Polymyxin B Sulphate 10,000 IU, Bacitracin zinc 500 IU, White
soft paraffin, B.P., no preservatives listed.

Topical Bacitracin
Sorbitan Trioleate
Wool Alcohols
Macrogol (4) Lauryl Ether
Polysorbate 85

?Bacitracin is stable only in the pH range 4.0-6.0.?
Pages 2-4 list various treatments of bacitracin that may interest you.

Topical Clindamycin
sodium lauroyl sarcosinate
stearic acid
cetostearyl alcohol
isostearyl alcohol
purified water.

Topical Erythromycin
Carbomer 980 
Sodium Hydroxide
SD Alcohol 
Methyl Salicylate 
Docusate Sodium 75% Solution 
Purified Water 
Ethanol 70 HSE*

Pevaryl? Topical Cream, anti-fungal
Liquid paraffin
Butylated hydroxyanisole (E320)
Benzoic acid (E210)

?Bactroban Cream contains 2% w/w mupirocin free acid present as
mupirocin calcium. This is the active ingredient. 1 g of cream
contains 21.5 mg mupirocin calcium equivalent to 20 mg mupirocin. Your
cream also contains inactive ingredients. These are benzyl alcohol,
xanthan gum, liquid paraffin, cetomacrogol 1000, stearyl alcohol,
cetyl alcohol, phenoxyethanol and purified water.?

Tetracycline, Topical
Cetostearyl Alcohol 5% 
Yellow Soft Paraffin 77% 
Liquid paraffin 10%

Containing 10% Sulphacetamide sodium in 70% Ethanol

    This is an interesting site. Please read the entire page. ?Any
suitable aqueous or nonaqueous solvent can be used. A particular
preferred solvent is water. Other suitable solvents include alcohol
solutions, especially ethanol. Alcohol should be used at
concentrations that will avoid precipitation of the components of the
present compositions. Enough of the solvent should be added so that
the total of all of the components in the composition is 100 wt./wt.
%, i.e., solvent to q.s. Typically, some portion of the solvent will
be used initially to solubilize the pharmaceutical agent prior to the
addition of the micelle-forming compounds.

The present compositions optionally contain a stabilizer and/or a
preservative. Phenolic compounds are particularly suited for this
purpose as they not only stabilize the composition, but they also
protect against bacterial growth and help absorption of the
composition. A phenolic compound will be understood as referring to a
compound having one or more hydroxy groups attached directly to a
benzene ring. Preferred phenolic compounds according to the present
invention include phenol and methyl phenol (also known as m-cresol),
and mixtures thereof.?

?It will be recognized by those skilled in the art that for many
pharmaceutical compositions it is usual to add at least one
antioxidant to prevent degradation and oxidation of the
pharmaceutically active ingredients. The antioxidant can be selected
from the group consisting of tocopherol, deteroxime mesylate, methyl
paraben, ethyl paraben, ascorbic acid and mixtures thereof, as well as
other antioxidants known in the pharmaceutical arts. A preferred
antioxidant is tocopherol. The parabens will also provide preservation
to the composition.?

   ?Benzoic acid, parabens, sorbic acid, ?Organic mercurials:mercury,
silver, thiomersal,phenylmercuric acetate, Phenolics:cresol,
chlorocresol, bisphenol, cetrimide, benzalkonium chloride

   This is only an excerpt; please click on the blue button labeled
?PDF? for the entire article.  ??p-hydroxybenzoate-based preservative
systems proved to be efficient in protecting the pharmaceutical
product against a challenge of wild and laboratory strains of Ps.
cepacia grown in the different conditions described above. The results
obtained suggest the usefulness, in the official methods for testing
pharmaceutical preservatives, of using wild microbial strains isolated
from the pharmaceutical environment. Metabolic adaptive responses,
capable of affecting the antimicrobial sensitivity of wild
micro-organisms used to challenge the preserved product, can be
detected by using cells grown in the unpreserved pharmaceutical

   ?Bacitracin is a polypeptide produced by the growth of an organism
of the licheniformis group of Bacillus subtilis (Fam. Bacillacaea). It
has a potency of not less than 40 bacitracin U/mg. It occurs as a
white to pale buff hygroscopic powder that is odorless or has a slight
odor. Its solutions deteriorate rapidly at room temperature. It is
freely soluble in water and soluble in alcohol. It is precipitated
from solution and is inactivated by salts of many of the heavy

   ?Preparation of Solutions: Should be dissolved in sodium chloride
injection containing 2% procaine. The concentration of the antibiotic
in the solution should not be less than 5 000 units/mL nor more than
10 000 units/mL.

Diluents containing parabens should not be used to reconstitute
bacitracin; cloudy solutions and precipitate formation have occurred.
Reconstitution of the 50 000 unit vial with 9.8 mL of diluent will
result in a concentration of 5 000 units/mL.

To be administered topically. 

Preparation of Solution: Solutions for topical application are
prepared by dissolving bacitracin in Sterile Water for Injection or
Sodium Chloride Injection in amounts to give the following
concentrations: skin, 500 units/mL; ophthalmic solutions, 500 to 1 000
units/mL; intranasal therapy, 250 units/mL; aerosol, 500 to 1 000

Availability And Storage: Each vial contains: bacitracin 50 000 units.
Store unreconstituted bacitracin in a refrigerator 2 to 8C. Solutions
are rapidly inactivated at room temperature but are stable for 1 week
when stored in a refrigerator 2 to 8C.?

About preservatives used in ophthalmic preparations
?Thimerosal sometimes triggers a sensitivity reaction, and other
mercurial compounds are unstable. Benzalkonium chloride compromises
both corneal epithelium and tear film. Some cationic detergents,
including chlorhexidine digluconate and polyquat, cause less
disruption at prophylactic concentrations.?

I could find no mention of topical Rifamin.

   I hope this information has helped you! If anything is unclear,
please ask for an Answer Clarification, and allow me to respond,
before you rate this answer.

Sincerely, Crabcakes

Search Terms
Composition + topical antibiotics
Bacitracin solution + preservatives
antibiotic solutions +  preservatives
topical antibiotics + preservatives
Rifampin + topical

Request for Answer Clarification by superg327-ga on 13 Sep 2006 07:31 PDT
Thank you - that answered the question that I asked just fine.  I have
no problems in closing this out and providing a high rating.  We
realized that we require more specific information.

Specifically - I should have asked the following

Can you provide a list of preservatives (to maintain drug stability)
that may be used with topical antibiotics that are soluble in alcohol,
and may be used as a preservative when the antibiotic is in solution
with alcohol. (eg Thimerasol).

So creams, paraffin, ointments, etc. would not be something we are interested in.

What is the best way to handle I post a new question and
close this one out?


Clarification of Answer by crabcakes-ga on 13 Sep 2006 09:34 PDT
Hello Superg,

  I appreciate the fact that you realize your question was not asked
as you intended. You may indeed close this question out, and ask
another, more detailed and specific question.

  I also humbly request that you consider the answer given to the
question asked when you rate, and not penalize the researcher, as so
often happens.

  When you ask a question on Google Answers, you may post numerous
question clarifications if you realize you did not word your question
as you intended, before it is answered.

  Thank you for being cognizant of your wording error and good luck
with your next question! (By the way, I did include some information
on alcohol as a preservative in the second half of the answer!)

  Sincerely, Crabcakes  :-)
superg327-ga rated this answer:5 out of 5 stars and gave an additional tip of: $5.00
comprehensive and detailed....thanks

Subject: Re: Preservatives for Drugs, Antibiotics
From: crabcakes-ga on 14 Sep 2006 22:40 PDT
Thank you SuperG, for the stars and the tip! Both are appreciated!
Sincerely, Crabcakes

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