3.4 II.3.4 Benzodiazepines by Hiroshi Seno and Hideki Hattori Introduction Benzodiazepines show antianxiety, hypnotic, anticonvulsant and muscle-relaxant eff ects. Th is group of drugs has wide safety dose ranges; it means that the ratio of the LD50 to the ED50 (therapeutic index) is high. Because of its safety, benzodiazepines are being widely used in the world. Some of benzodiazepines are also being abused or used for so-called “ drug facilitated sexual assault”, and thus they are under the control of the Narcotics and Psychotropics Control Law; in Japan, triazolam abuse has become one of the serious social problems. In this chapter, a GC/MS method for simultaneous analysis of 22 kinds of benzodiazepines listed in > Table 4.1 is described. In addition, the LC/MS analysis of triazolam, and its metabolites 4-hydroxy- triazolam and α-hydroxytriazolam is also presented. GC/MS analysis of benzodiazepines in blood and urine Reagents and their preparation • Th e pure powder of the 22 kinds of benzodiazepines was donated by each pharmaceutical manufacturers according to the authors’ request a (some of benzodiazepines now obtaina- ble from Sigma, St. Louis, MO, USA). • 1 M Sodium bicarbonate solution: a 8.4-g aliquot of sodium bicarbonate is dissolved in distilled water to prepare 100 mL solution. • 2 M Sodium acetate solution: a 27.5-g aliquot of sodium acetate is dissolved in distilled water to prepare 100 mL solution. GC/MS conditions Column: a DB-5 fused silica capillary column (30 m × 0.25 mm i.d., fi lm thickness 0.25 µm, J & W Scientifi c, Folsom, CA, USA). GC conditions; instrument: a GC-17A gas chromatograph (Shimadzu Corp., Kyoto, Japan); column (oven) temperature: 150 °C (1 min) → 20 °C/min → 300 °C (6.5 min); injection tempera- ture: 250 °C; carrier gas: He; its fl ow rate: 0.9 mL/min; sample injection: splitless mode for 1 min, followed by the split mode. MS conditions: a QP-5050A mass spectrometer (Shimadzu Corp.); ionization: EI; electron energy 70 eV; interface temperature: 250 °C. © Springer-Verlag Berlin Heidelberg 2005 284 Benzodiazepines ⊡ Table 4.1 Chemical structures of benzodiazepines Compound R1 R2 R3 R4 diazepam Cl CH3 H– fludiazepam Cl CH3 F– flurazepam Cl C2H5 F– (CH2)2N C2H5 prazepam Cl CH2 7◃ H– flutoprazepam Cl CH2 7◃ F– dipotassium Cl H H 3: CHCOOK clorazepate medazepam Cl CH3 H 2: CH2 clordiazepoxide Cl – H 2: CNHCH3; 4: N→O nitrazepam NO2 HH– nimetazepam NO2 CH3 H– clonazepam NO2 HCl– flunitrazepam NO2 CH3 F– bromazepam Br H – 5: C-pyridine tofisopam CH3CO – H 1: CHC2H5; 2: C–CH3; 3: N; 3’: –OCH3; 4’: –OCH3; 8: –COCH3 oxazolam Cl H H 4, 5: 2-methyloxazolo mexazolam Cl H Cl 4, 5: 3-methyloxazolo estazolam Cl – H 1, 2: triazolo alprazolam Cl – H 1, 2: 1-methyltriazolo triazolam Cl – Cl 1, 2: 1-methyltriazolo midazolam Cl – F 1, 2: 1-methyltriazolo etizolam – – Cl 1, 2: 1-methyltriazolo; 1, 5: 7-ethylthieno brotizolam – – Cl 1, 2: 1-methyltriazolo; 1, 5: 7-bromothieno GC/MS analysis of benzodiazepines in blood and urine 285 Procedure i. A 1-mL volume of whole blood or urine is mixed well with 8.5 mL distilled warter b in a 15-mL volume glass centrifuge tube with a ground-in stopper, followed by addition of 0.5 mL of 1 M sodium bicarbonate solution. ii. Aft er it is vortex-mixed, it is centrifuged at 3,000 rpm for 10 min to obtain a supernatant fraction. iii. An Oasis HLB 3cc solid-phase extraction cartridge (Waters, Milford, MA, USA) is set on a vacuum manifold, and 3 mL methanol and 3 mL water are passed through the cartridge for conditioningc. iv. Th e supernatant fraction prepared at the step ii) is loaded on the Oasis HLB cartridge c. v. Th e cartridge is washed with 3 mL distilled water d. vi. A target drug is eluted with 3 mL chloroform c into a 5-mL volume glass tube with a conical bottom. vii. Th e chloroform layer (lower phase) is carefully transferred to a 4-mL volume glass vial using a Pasteur pipette. viii. Th e organic layer is evaporated to dryness under a stream of nitrogen. ix. Th e residue is dissolved in 50 µL methanol and a 2-µL aliquot is injected into GC/MSe. Assessment and some comments on the method Th e recovery rates of the drugs from blood and urine were not less than 60 %. > Figure 4.1 shows a total ion chromatogram (TIC) for the authentic standards of benzodiazepines dis- solved in methanol. In this chromatogram, separation between dipotassium clorazepate and ⊡ Figure 4.1 TIC for the authentic standards of 22 benzodiazepines. 1: medazepam, 2: fludiazepam, 3: diazepam, 4: dipotassium clorazepate, 5: chlordiazepoxide, 6: oxazolam, 7: midazolam, 8: flunitrazepam, 9: flutoprazepam, 10: bromazepam, 11: prazepam, 12: nimetazepam, 13: mexazolam, 14: flurazepam, 15: nitrazepam, 16: clonazepam, 17: estazolam, 18: alprazolam, 19: tofisopam, 20: etizolam, 21: triazolam, 22: brotizolam. 286 Benzodiazepines chlordizepoxide, between fl utoprazepam and bromazepam and between fl urazepam and nitrazepam could not be achieved; the peak of tofi sopam showed tailing. Th e separation of other drugs was relatively good. Th e retention times, molecular weights and principal mass spectral ions of benzodiazepines are shown in > Table 4.2. Th e quantitatione of the drugs was made by selected ion monitoring (SIM). Excellent quan- titativeness could be confi rmed in the range of 10–1,000 ng/mL of diazepam, fl udiazepam, fl urazepam, prazepam, fl utoprazepam, dipotassium clorazepate, medazepam, chlordiazepoxide, fl unitrazepam, alprazolam, midazolam, etizolam and brotizolam for both blood and urine. Th e detection limits of these 13 drugs were 1–5 ng/mL. For nitrazepam, mexazolam, nimetazepam, clonazepam, bromazepam, tofi sopam, estazolam and triazolam, quantitativeness could be observed in the range of 50–1,000 ng/mL with detection limits of 10–20 ng/mL, and for oxa- zolam it could be observed in the range of 200–1,000 ng/mL with detection limits of 50 ng/mL in urine and 100 ng/mL in blood. ⊡ Table 4.2 Retention times and principal mass spectral ions of benzodiazepines measured by GC/MS Compound Retention Moleculer Principal ions m/z (% intensity) time (min) weight medazepam 7.97 270 207 (100), 242 (91), 244 (30), 270 (20),165 (15) fludiazepam 8.68 302 274 (100), 301 (96), 302 (92), 109 (43), 283 (37) diazepam 8.94 284 283 (100), 256 (94), 284 (88), 221 (36), 110 (31) dipotassium 9.28 409 242 (100), 270 (69), 103 (34), 89 (33), 76 (30) clorazepate chlordiazepoxide 9.31 299 282 (100), 124 (20), 247 (16), 220 (14), 89 (11) oxazolam 9.72 328 251 (100), 253 (30), 70 (30), 105 (13), 77 (12) midazolam 9.78 325 310 (100), 312 (30), 325 (20), 163 (12), 111 (12) flunitrazepam 9.91 313 285 (100), 312 (99), 313 (95), 266 (58), 238 (37) flutoprazepam 10.00 342 55 (100), 313 (67), 109 (61), 287 (42), 259 (37), 342 (29) bromazepam 10.01 315 90 (100), 326 (92), 315 (91), 77 (91), 317 (86) prazepam 10.10 324 55 (100), 91 (91), 269 (75), 295 (68), 324 (46) 241 (36) nimetazepam 10.30 295 267 (100), 294 (77), 248 (63), 295 (62), 220 (34) mexazolam 10.75 363 251 (100), 253 (30), 70 (22), 139 (11), 236 (9) flurazepam 10.83 387 86 (100), 99 (7), 58 (6), 387 (2) nitrazepam 10.91 281 280 (100), 253 (95), 234 (80), 264 (61), 206 (58) clonazepam 11.56 315 280 (100), 314 (87), 315 (68), 288 (54), 89 (52) estazolam 12.03 294 259 (100), 293 (65), 294 (64), 205 (59), 89 (50) alprazolam 12.42 308 279 (100), 273 (90), 308 (88), 204 (84), 102 (82) tofisopam 12.97 382 382 (100), 326 (87), 341 (63), 353 (33), 156 (31) etizolam 13.32 342 342 (100), 344 (47), 313 (37), 266 (31), 125 (24) triazolam 13.50 342 313 (100), 315 (76), 238 (71), 75 (62), 342 (52) brotizolam 13.82 392 394 (100), 392 (77), 245 (43), 118 (38), 123 (27) * The ions used for SIM are shown in boldfaces. LC/MS analysis of triazolam and its metabolites 287 In the analysis of benzodiazepines by GC and GC/MS, the decomposition of drugs due to heat frequently takes place. Th e decomposition is marked especially for oxazolam, cloxazolam, mexazolam, fl utazolam and haloxazolam having oxazolo rings in their structures [1]. In such cases, the relatively low injection temperature and the use of a wide-bore capillary column with short length (15 m) can protect the drugs from their heat decomposition to some extent. For nitro-group containing drugs, such as nitrazepam, nimetazepam, clonazepam and fl unitrazepam, the nitro group is rapidly metabolized into an amino group (in the 7-position) aft er being absorbed into human body [2]. Th e above GC/MS method deals with detection and identifi cation of unchanged benzodi- azepines. To detect benzodiazepine metabolites from urine specimens, it is necessary to hydro- lyze the glucuronate conjugates of the drugs using β-glucuronidase; the resulting free forms with hydroxyl groups should be derivatized before GC (/MS) analysis. When benzodiazepines are treated in strong acid, they are hydrolyzed into benzophenones, which are very stable against heat; the benzophenones can be also obtained from the hydroxyl- ated metabilites and their conjugates together with unchanged forms of benzodiazepines [3–5]. Using the benzophenone, detection and identifi cation of a benzodiazepine or its metabolites can be achieved by GC or GC/MS without any derivatization. However, it should be noted that an unchanged benzodiazepine, its hydroxylated metabolite and its glucuronide metabolite all give the same benzophenone; also there are many cases in which diff erent benzodiazepines give the same benzophenone.