Oxytocin: Storage, Labeling and Monograph Issues

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Oxytocin Storage, Labeling and Monograph Issues

• Larry Callahan, Ph.D.
• USP, Rockville, Maryland

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U. S. Pharmacopeia/USP DQI

• USP was founded in 1820 by the medical community
  to standardize formulations
• Leading non-government pharmacopeia worldwide
• USP Drug Quality and Information Program
  current cooperative agreement with U.S. Agency
  for International Development (USAID) that
  provides technical assistance in more than 20
  countries. Its set objectives
• To improve availability and appropriate use of
  good quality pharmaceutical products
• To increase availability and use of unbiased
  health information

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USP Monograph Revision Process

• Monographs are voluntary
• Monograph (revisions) submitted or suggested by
  sponsor
• Sponsor can be anyone, but is usually a
  manufacturer
• Monograph drafted by liaison
• Publication in PF
• Comments received from public (comment period
  usually about 5 months)
• Monograph revised based on comment or forwarded
  to Expert Committee/Board of Trustees for
  approval
• Monograph published in USP-NF
• Monograph becomes Official

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USPNF Today
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Effect of USP Monograph

• USP standards are enforceable by the U.S. FDA and
  other governments
• USP standards are enforceable throughout the
  lifetime of the product or dosage form
• From production to consumption
• Not necessary to perform every USP test on every
  batch or vial but must pass all USP tests if
  tested
• Monographs are tied to products, not
  manufacturers every manufacturer must meet same
  monograph requirements
• USP, BP, and JP have monographs on dosage forms
  EP has no product monographs

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Oxytocin Injection Monograph History

• Oxytocin activity discovered by Dale 1909.
• Oxytocin is first reported synthesized by Vincent
  du Vigneaud in 1953. (Won Noble Prize in 1955)
• Monograph first appeared in USP XV (1955) Animal
  derived. 10 USP Units per mL. Packaging and
  Storage (PS)Type I glass (no temperature req.)
• USP XVI (1960) Allows for synthetic product.
  PS-Avoid excessive temperature pH 2.5-3.6
• USP XVII (1965) PS-Refrigerator, Do not freeze
  Expiration date 3 years from assay date. pH
  2.5-4.5
• USP XIX (1975) PSDo not freeze. No expiration
  date requirement.
• USPXX (1980) 85-120 of label.

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Oxytocin Injection Monograph History-2

• USP 23 1st Supp. (1995) 90-110 of label. HPLC
  assay introduced. pH 3.0-5.0 (Oxytocin monograph
  becomes official. Greater than 400 USP units per
  mL. PSrefrigerator).
• USP 28 (2005) PSStore between 2 and 8C. Do
  not freeze removed from monograph.
• Reason for most recent monograph change
  Instability reported at 21C and 30C from one
  manufacturer. At 30C, 10-12 degradation over 12
  months. At 21C, 3-5 degradation over 24 months.
  At 5C, product stable for 60 months. No
  information on pH or formulation.

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Current Monographs in Pharmacopeias

• USP 29 Potency 90-110 of label PS2-8C pH
  3.0-5.0
• EP 5.4 (No Product Monographs) Storage Bulk
  Solution 2-8C pH 3.0-5.0
• JP (2001) 85-120 of label. Bioassay (Chicken).
  PSIn a cold place (lt 15C avoid freezing.)
• BP 90-110 of label. pH 3.5 to 4.5 no current
  temperature criteria (Had temperature control in
  1995 of 2-15C)

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Current U.S. Manufacturer Storage Conditions,
Typical Expiration Dates

• American Pharmaceutical Partners Controlled Room
  Temperature (From MSDS). Expiration labeling 9
  months (verbally reported).
• Parkedale (King) 2-8C Allows short excursions 30
  days at 15-25C. Expiration date 2-3 years from
  preparation (Martindale). Acetate buffered?
• Novartis (New Zealand) 2-8C Allows 30C for 3
  months.

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Oxytocin Chemistry and Stability

• Chemical Structure
• MW 1007.2

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Degradation Pathways

• Time scale for degradation at ambient
  temperatures weeks, not hours
• Disulfides (reactions)
• Reduction
• Oxidation
• Disulfide exchange (scrambling)
• Temperature and pH would have some effect but
  mostly effected by added substances or initial
  material (free thiols, oxidizers or reductants).
• Amides (Asparagine (ASN), Glutamine (GLN),
  C-terminal (C-NH2), Peptide backbone)
• Deamidation (GLN and ASN)
• Half-life of ASN in proteins/peptides at 37.0, pH
  7.4 (0.5 days-500 days)
• Half-life of GLN proteins/peptides at 37.0. pH
  7.4 (600 days-2000 days)
• From Robinson, N. E. and Robinson, A. B. (2004)
• Molecular Clocks Deamidation of Asparaginyl and
  Glutaminyl Residues in Peptides and Proteins.
• http//book.deamidation.org/MolecularClocks.pdf

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Degradation Pathways-2

• Deamidation Pathways
• Imide (ring) formation, can be very fast
  dependent on nearest neighbor, conformation
  predominantly, some temperature and pH effects.
• Hydrolysis much slower, dependence on sequence,
  temperature and pH effects predominate. Peptide
  backbone also effected.
• Hydrolysis can be both acid and base catalyzed.
• Oxytocin can degrade by both imide formation and
  hydrolysis

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pH and Hydrolysis of Peptides
Hydrolysis of small peptide from polymeric
support at 25C. From Kahne and Still,
J.Am.Chem.Soc. 1107529-7534 (1988)
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Possible Changes in Storage Conditions for
Product Monograph

• Potential Storage Temperatures
• No required temperature conditions
• Controlled room temperature (monitor
  temperature allow excursions)
• Controlled cold temperature (monitor
  temperature allow excursions)
• Allow dual storage conditions but expiration
  date must be based on a single storage condition

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Storage Temperature Definitions

• Cold Any temperature not exceeding 8 (46F). A
  refrigerator is a cold place in which the
  temperature is maintained thermostatically
  between 2 and 8 (36 and 46F).
• Cool Any temperature between 8 and 15C (46
  and 59F). An article for which storage in a cool
  place is directed may, alternatively, be stored
  and distributed in a refrigerator, unless
  otherwise specified by the individual monograph.
• Room Temperature The temperature prevailing in
  a working area.

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Storage Temperature Definitions-2

• Controlled Room Temperature A temperature
  maintained thermostatically that encompasses the
  usual and customary working environment of 20 to
  25C (68 to 77F) that results in a mean
  kinetic temperature calculated to be not more
  than 25C and that allows for excursions between
  15 and 30 (59 and 86F) that are experienced
  in pharmacies, hospitals, and warehouses.
  Provided the mean kinetic temperature remains in
  the allowed range, transient spikes up to 40C
  are permitted as long as they do not exceed 24
  hours. Spikes above 40C may be permitted if the
  manufacturer so instructs. Articles may be
  labeled for storage at controlled room
  temperature or at up to 25, or at other
  wording based on the same mean kinetic
  temperature. The mean kinetic temperature is a
  calculated value that may be used as an
  isothermal storage temperature that simulates the
  non-isothermal effects of storage temperature
  variations.

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Storage Temperature Definitions-3

• Controlled Cold Temperature This is defined as
  the temperature maintained thermostatically
  between 2 and 8C (36 and 46 F) that allows
  for excursions in temperatures between 0 and
  15C (32 and 59F) that may be experienced
  during storage, shipping, and distribution such
  that the allowable calculated MKT is not more
  than 8C (46 F). Transient spikes up to 25C
  (77F) are permitted provided that such spikes do
  not exceed 24 hours, unless supported by data or
  the manufacturer instructs otherwise.

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Consequences of Higher Storage Temperature

• Reduced Shelf-Life Due to an Increase in
  Hydrolysis Rate
• More degradants
• Greater Chance of Catastrophic Failure?
• Product no longer in solution or completely
  degraded, precipitation, aggregation, adsorption.
• Catastrophic failure (precipitation) observed in
  dilute solution in lactated ringer solutions
  after 35 days at 30C. Product seemed fine at 28
  days. Cause not specified. Ringer contains
  calcium. Not seen in other solutions. See Trissel
  et al. Int. J. Pharm. Comp. 10156-158 (2006).
• Microbial growth more likely

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How to Increase Shelf-Life

• Find optimum pH tighter control on pH. (USP
  Nasal Solution 3.7-4.3 no storage temp
  specified)
• Lyophillization (freeze-dried) long shelf-life
  20 years (Current International RS)
• More expensive, very little material 20 mg
• Reconstitution could be problematic
• Change specification in the monograph. Allow
  90-125 of label amount. This would allow
  overloading and a longer shelf-life.
• The biological half-life of Oxytocin is five
  minutes. This should allow slightly higher dosing
  without adverse consequences.

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Other Possible Changes in Oxytocin Monographs

• Oxytocin
• Eliminate animal test (rat uterus contraction).
• Replace with LC-MS to allow identification and
  quantification of impurities and related
  compounds.
• Oxytocin Injection
• Add a related compounds test to monitor the
  extent of degradation.

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Information Needed for Further Monograph
Development

• Rate of Failure (Bad Vials Catastrophic failure)
  
• Identity of the Degradants
• Bioactivity of the degradants
• Oxytocin Agonist or Antagonist
• Substrate or inhibitor of Oxytocinase (a plasma
  protease produced during pregnancy that appears
  to target and inactivate oxytocin. In the absence
  of oxytocinase, the elimination half-life is 3-5
  minutes significantly shorter in its presence.

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Thank you for your attention

• Larry Callahan, Ph.D.
• Scientist, Standards Development
• United States Pharmacopeia
• 12601 Twinbrook Parkway
• Rockville, MD 20852
• www.usp.orglnc_at_usp.org