Identification and Quantitation of Hydromorphone Hydrochloride
in Palladone^® (Extended Time-Release) Capsules

Pamela R. Smith,* Amanda K. Frohwein, Patrick A. Hays, and Ira S. Lurie
U.S. Department of Justice
Drug Enforcement Administration
Special Testing and Research Laboratory
22624 Dulles Summit Court
Dulles, VA 20166
[email address withheld at author’s request]

ABSTRACT: Palladone^® is an extended time-release formulation of hydromorphone hydrochloride. The time-release matrix presents some unusual analytical challenges (especially for quantitation). FTIR (GC/IRD), 400 MHz 1H-NMR, GC/MS, and CE (DAD) data are presented, enabling qualitative and quantitative analyses of Palladone^® formulations.

KEYWORDS: Palladone^®, Hydromorphone, Time-Release, Synthetic Opiate, Forensic Chemistry

Hydromorphone

Introduction

Hydromorphone is a synthetic opiate derived from morphine. It is a controlled substance (Schedule II) under the U.S. Controlled Substances Act. Palladone^® is an extended time-release formulation of hydromorphone hydrochloride produced by Purdue Pharma (1). Controlled release formulations are usually solid dosage forms (capsules or tablets) that contain individual pellets that, when administered orally, slowly release the drug over a longer time frame (that is, different types of pellets in the formulation dissolve at different rates, thereby giving a lower but much longer lasting, steady-state concentration of the drug). Currently, Palladone^® capsules are available in the following concentrations: 8, 12, 16, and 32 milligrams/capsule.

Synthetic opiates are popular among drug abusers, and are therefore occasionally submitted for analysis to forensic laboratories. Controlled release formulations present challenges for both qualitative and (especially) quantitative analysis. In order to accurately quantitate the drug, it must be possible to separate the drug from the matrix in a quantitative manner. This study presents both qualitative and quantitative methodologies for the analyses of Palladone^® capsules.

Experimental

Chemicals and Reagents
Buffers and solutions were products of MicroSolv Technology (Eatontown, NJ). Chloroform, methanol, and acetone were products of Burdick and Jackson Laboratories (Muskegon, MI). CDCl₃, D₂O, and TMS were products of Sigma-Aldrich (Milwaukee, WI).

Qualitative Analyses

Vapor Phase Infrared Spectroscopy
The FTIR spectrum was obtained on a Nicolet 6700 FTIR GC‑IRD (Figure 1).

Figure 1. Vapor Phase FTIR of Hydromorphone.

 

Nuclear Magnetic Resonance Spectroscopy
One dimensional NMR analyses of hydromorphone and Palladone^® were performed on a Varian Mercury 400 MHz NMR using a 5 mm Nalorac Indirect Detection probe.

Hydromorphone hydrochloride has four isomeric forms (two keto [Ia,Ib] and two enol [IIa,IIb] forms (Figure 2)), each exhibiting two possible N-methyl orientations) under acidic conditions in either D₂O or CD₃OD. The relative proportions of these forms in solution depends on the solvent and the solution pH. Use of NMR for identification and quantitation of hydromorphone hydrochloride is therefore not recommended, because great care would be required to identify and properly integrate the signals generated by the four keto-enol forms. However, by utilizing a basic extraction with sodium bicarbonate into CDCl₃, only one form of hydromorphone base is observed (Figure 3).

Figure 2. Keto-Enol Structures of Hydromorphone Hydrochloride.

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Figure 3. Hydromorphone Base in CDCl₃.

Workup of Palladone^® for NMR Analysis: Weigh 20 milligrams of Palladone^® into a 15 mL centrifuge tube. Add 0.5 mL saturated sodium bicarbonate in D₂O and 1 mL CDCl₃ containing 0.03% TMS, and sonicate for 15 minutes. This produces a white emulsion, which is then centrifuged. The CDCl₃ (lower) layer is then isolated and dried over anhydrous sodium sulfate, filtered, and transferred to an NMR tube. The resulting spectrum (Figure 4) displays both the hydromorphone peaks and the peaks from the capsule matrix material(s) (compare with Figure 3).

Figure 4. Palladone^® (basified) in CDCl₃ (Note: Brackets indicate location of hydromorphone base peaks for identification).

Gas Chromatography/Mass Spectrometry

Instrument:	Agilent 6890N with an Agilent 5973 MSD
Column:	DB-1, 30 m x 0.25 mm x 0.25 μm film thickness
Injector Temperature:	280 °C
Oven Temperature:	90 °C for 2 minutes, 14 °C/minute to 280 °C
Carrier Gas:	Helium with split ratio = 25:1
Scan Range:	34 - 550 amu
Electron Ionization:	70 eV

Hydromorphone has a chemical formula of C₁₇H₁₉NO₃, and a molecular weight of 285.34. The mass spectrum shows the molecular ion (which is also the base peak) at m/z 285 (Figure 5).

Figure 5. Mass Spectrum of Hydromorphone .

Quantitative (Capillary Electrophoresis) Procedures

As noted above, Palladone^® presents some challenges for quantitative analysis. When utilizing GC, HPLC, or many modes of CE, the peak shapes are broad and non-symmetrical, causing difficulties for quantitation. In this study capillary electrophoresis (CE) was employed utilizing a dynamic coating with a chiral run buffer. Previous studies have shown that this method has improved peak shape over dynamic coatings without chiral additives (2). As shown, this approach resulted in excellent peak shape (Figure 6).

Figure 6. CE of a Palladone^® Tablet; Peak Identities: (a) Hydromorphone; and (b) Procaine (IS).

An additional study was conducted to determine a method for quantitative recovery of hydromorphone hydrochloride from Palladone^® capsules. The recovery study showed that using a mixture of 20% methanol : 80% injection solvent to prepare the sample gives a recovery of greater than 96 percent from any of the four Palladone^® concentrations (Figure 7).

Figure 7. Recovery of Hydromorphone Hydrochloride from Palladone^®.

Capillary Electrophoresis Procedures
Run Buffer: CElixir accelerator solution B (pH 2.5) + 50 mM 2-hydroxypropyl-β-cyclodextrin (HP-β-CD) (Sigma). Weigh 1576 mg of HP-β-CD into a 50 mL Erlenmeyer flask. Pipette 20.0 mL of CElixir accelerator solution B (pH 2.5) and shake vigorously. Filter into 22 mL Teflon PVA vials (Cole Parmer) using a 0.45 μm, 25 mm regenerated cellulose filter.

Injection Solvent: Weigh 1,034 milligrams of sodium phosphate monobasic into a 100 mL volumetric flask. Dilute to volume with HPLC grade water. Adjust to approximately pH 2.6 using phosphoric acid added dropwise. Transfer contents into a 2000 mL volumetric flask with the aid of HPLC grade water. Dilute to volume with HPLC grade water. This final solution contains 3.75 mM phosphate (pH 3.2).

Internal Standard Stock Solution (ISSS): Weigh an appropriate amount of procaine hydrochloride into a volumetric flask to obtain a final concentration of approximately 1.0 mg/mL. Dilute to volume with 20% methanol : 80% injection solvent.

Standard Solution: Weigh an appropriate amount of standard hydromorphone hydrochloride into a volumetric flask to obtain a final concentration of approximately 0.10 mg/mL. Pipette an appropriate amount of internal standard solution to obtain a final concentration of 0.1 mg/mL. Dilute to volume with 20% methanol : 80% injection solvent. Filter approximately 1.0 mL of solution with a 0.45 μm, 25 mm regenerated cellulose filter into a 2.0 mL glass vial (Agilent part # 5182-0567). Care should be taken to ensure that there are no air bubbles on the bottom of the glass vial. Cap the vial with a polypropylene cap (Agilent part # 5182-9697).

Sample Preparation: Weigh an appropriate amount of sample into a volumetric flask so that the final hydromorphone hydrochloride concentration is approximately equal to that of the standard solution. Pipette an appropriate amount of internal standard solution to obtain a final concentration of 0.1 mg/mL. Dilute to volume with 20% methanol : 80% injection solvent. If the sample is a time-release preparation, it should be sonicated for at least one hour. Filter approximately 1.0 mL of sample solution with a 0.45 μm, 25 mm regenerated cellulose filter into a 2.0 mL glass vial (Agilent part # 5182-0567). Once again, care should be taken to ensure that there are no air bubbles on the bottom of the glass vial. Cap the vial with a polypropylene cap (Agilent part # 5182-9697).

Instrumental Conditions:

Validation Criteria:

Linearity Range:	0.0217 mg/mL + 0.9774 mg/mL
Repeatability:	RSD < 0.81 %
Accuracy:	E % < 3.9 %
Correlation Coefficient (R 2):	0.99995

References

1. Anonymous. Pharmaceutical update: Palladone now available in pharmacies. Narcotics Digest Weekly 2005;4(13):3.

2. Lurie IS, Hays PA, Parker K. Capillary electrophoresis analysis of a wide variety of seized drugs using the same capillary with dynamic coating. Electrophoresis 2004;25(10-11):1580-91.

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