Oxytocin: Storage, Labeling and Monograph Issues

1. Oxytocin: Storage, Labeling and Monograph Issues Larry Callahan, Ph.D. USP, Rockville, Maryland

2. 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

3. 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

4. USP–NF Today

5. 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

6. 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 (P&S)–Type I glass (no temperature req.) • USP XVI (1960) Allows for synthetic product. P&S-Avoid excessive temperature; pH 2.5-3.6 • USP XVII (1965) P&S-Refrigerator, Do not freeze; Expiration date 3 years from assay date. pH 2.5-4.5 • USP XIX (1975) P&S–Do not freeze. No expiration date requirement. • USPXX (1980) 85-120% of label.

7. 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. P&S–refrigerator). • USP 28 (2005) P&S–Store between 2° and 8°C. Do not freeze removed from monograph. • Reason for most recent monograph change — Instability reported at 21°C and 30°C from one manufacturer. At 30°C, 10-12% degradation over 12 months. At 21°C, 3-5% degradation over 24 months. At 5°C, product stable for 60 months. No information on pH or formulation.

8. Current Monographs in Pharmacopeias • USP 29 Potency 90-110% of label; P&S–2-8°C; pH 3.0-5.0 • EP 5.4 (No Product Monographs) Storage Bulk Solution 2-8°C; pH 3.0-5.0 • JP (2001) 85-120% of label. Bioassay (Chicken). P&S–In a cold place (<= 15C; avoid freezing.) • BP 90-110% of label. pH 3.5 to 4.5; no current temperature criteria (Had temperature control in 1995 of 2-15°C)

9. 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) 2-8°C Allows short excursions 30 days at 15-25°C. Expiration date 2-3 years from preparation (Martindale). Acetate buffered? • Novartis (New Zealand) 2-8°C Allows 30°C for 3 months.

10. Oxytocin Chemistry and Stability • Chemical Structure • MW 1007.2

11. 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

12. 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

13. pH and Hydrolysis of Peptides Hydrolysis of small peptide from polymeric support at 25°C. From Kahne and Still, J.Am.Chem.Soc. 110:7529-7534 (1988)

14. 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

15. Storage Temperature Definitions • Cold — Any temperature not exceeding 8° (46°F). A refrigerator is a cold place in which the temperature is maintained thermostatically between 2° and 8° (36° and 46°F). • Cool — Any temperature between 8° and 15°C (46° and 59°F). 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.

16. Storage Temperature Definitions-2 • Controlled Room Temperature — A temperature maintained thermostatically that encompasses the usual and customary working environment of 20° to 25°C (68° to 77°F); that results in a mean kinetic temperature calculated to be not more than 25°C; and that allows for excursions between 15° and 30° (59° and 86°F) that are experienced in pharmacies, hospitals, and warehouses. Provided the mean kinetic temperature remains in the allowed range, transient spikes up to 40°C are permitted as long as they do not exceed 24 hours. Spikes above 40°C 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.

17. Storage Temperature Definitions-3 • Controlled Cold Temperature — This is defined as the temperature maintained thermostatically between 2° and 8°C (36° and 46° F) that allows for excursions in temperatures between 0° and 15°C (32° and 59°F) that may be experienced during storage, shipping, and distribution such that the allowable calculated MKT is not more than 8°C (46° F). Transient spikes up to 25°C (77°F) are permitted provided that such spikes do not exceed 24 hours, unless supported by data or the manufacturer instructs otherwise.

18. 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 30°C. 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. 10:156-158 (2006). • Microbial growth more likely

19. 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.

20. 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.

21. 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.

22. Thank you for your attention Larry Callahan, Ph.D. Scientist, Standards Development United States Pharmacopeia 12601 Twinbrook Parkway Rockville, MD 20852 www.usp.orglnc@usp.org