Other Drug Analytes

The antifilarial methyl-[5-(a-ainino-4-fluorobenzyl)benzimidazol-2-yl]carbainate (MAFBC) and four metabolites (e.g., flubendazole and decarbamoylated-MAFBC) were extracted fi om plasma and separated on a Cjg column (A = 291 nm) using a 70/30 - 45/55 (at 10.25 min hold 2.75 min) - 30/70 (at 17.56 min hold 3 min) water (50 mM phosphate to pH 4.0 with H3P04)/(75/25 methanol/acetonitrile) gradient [55,7]. Good peak shapes and resolution were obtained. The calibration range used was 10-500ng/mL and quantitation limits of lOng/mL (parent) and 20-1000 ng/mL for the metabolites (analyte dependent) were reported. 

Five antidiabetic drugs (tolbutamide, chlorpropamide, glipizide, gliclazide, glibenclamide) were isolated from blood or serum and separated on a C]g column (A = 225nm). A 25-min 58/42 (hold 11 min)- 71/29 (at 15 min hold 10 min) 

The antimicrobial thimerosal is used as a preservative in hepatitis vaccines. Two degradation compounds (dithiosalicylic acid, thiosalicylic acid) were separated h om their parent on a C g column (A = 226 nm) using a 65/35/0.9 methanol/water/ H3PO4 mobile phase [559]. Elution was complete in 12 min. A calibration curve from 20 to 80 g/mL was used and a 5 g/mL detection limit (S/N = 3) was rqiorted. 

Pimobendan and its liver microsomal metabolite O-desmethylpimobendan were isolated from an incubate and separated on a 40°C C g (A = 338 nm, ex 405 nm, em) using a 3/1/4 methanol/acetonitrile/water (0.6% ammonium acetate) mobile phase [561]. Good peak shapes and resolution were achieved and elution was complete in 6 min. A linear range of 0.1-200 ng injected and a detection limit of 0.1 ng injected were reported. 

Chloroquine (an antibacterial) and its mono- and bisdesethylchloroquine metabolites were extracted from human microsomes and separated on a C colunm (,i = 250nm, ex 380 nm, em) using an isocratic 70/30/1 methanol/water/ triethylamine mobile phase [562], Elution was complete in 35 min, all peaks were broad, and chloroquine was tailed. Since these are basic amine confounds, the addition of TFA could help peak shape. Also, it should be noted that C, columns are not resistant to basic solutions, the bonded phase being readily cleaved under such conditions. Therefore, a precolumn or the use of a Cg or Cjg column should be considered. Two separate linear curve regions were cited 78-1250 nM and 1250-20000 nM with a quantitation limit of 78nM (S/N = 3). 

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Musumarra et al. [43] identified miconazole and other drugs by principal components analysis of standardized thin-layer chromatographic data in four eluent systems. The eluents, ethylacetate methanol 30% ammonium hydroxide (85 10 15), cyclohexane-toluene-diethylamine (65 25 10), ethylacetate chloroform (50 50), and acetone with the plates dipped in potassium hydroxide solution, provided a two-component model that accounts for 73% of the total variance. The scores plot allowed the restriction of the range of inquiry to a few candidates. This result is of great practical significance in analytical toxicology, especially when account is taken of the cost, the time, the analytical instrumentation and the simplicity of the calculations required by the method. 

In addition to the above cited typical examples there are a quite a few other drug substances which have been duly assayed by NMR-spectroscopy, thus suggesting the versatility of this technique as an important analytical tool. 

Barbiturates represent a class of sedative and hypnotic drugs employed extensively in medicine. RIA provides a rapid, sensitive specific and reliable means for their determination in plasma levels upto 5 ng without indulging in any type of extraction, filtration or evaporation as required for other conventional analytical methods. ... 

Multitarget forensic applications of HPLC for other drug classes are also available in the literature. Josefsson et al. [77] applied HPLC-MS-MS to the determination of 19 neuroleptics and their major metabolites in human tissues and body fluids. Optimal separation was achieved using a cyano column within a 9 min gradient run. Detection was curried out in SRM reaching LQDs down to the lower ng/mL level, although more than a 10-fold difference in signal response was observed between analytes. The method was subjected to partial validation only. 

Antipsychotics versus psychotherapy (two comparative studies). Both studies covered large, statistically equivalent groups of patients with productive symptoms one study compared group psychotherapy and antipsychotics the other compared analytically orientated individual therapy and antipsychotics. The results were similar inasmuch as both trials showed the drug therapy to be markedly superior in almost all clinically relevant characteristics and symptoms. 

NDA applicants are required to submit a list of all excipients (as well as other drug components), used in the manufacture of a proposed new drug. Additionally, the applicant must provide sufficient information to establish that the use of each excipient is safe for its intended use, at its intended quantity. This information includes safety data, a statement of the composition, specifications, and any analytical methods used for the excipient. When a USP/NF monograph exists for an excipient, the applicant may state that the excipient in the drug will comply with the standards in the monograph instead of providing composition, specification, and analytical method information. The required safety information includes... 

A similar procedure based on a dilution of milk sample and SPE was presented for CEF residues. The authors reported that the contamination of CEF was avoided by sequentially washing the glassware with 1 M hydrochloric acid, water, and MeOH. The stability of the sample extract was studied, and a significant decrease in recovery was noted if samples were kept longer than 24 hours. In comparison to the previous procedure, a higher recovery was obtained (92% with CV 3.9%) (58). Both procedures were tested for possible interference of other drugs that may be found in raw milk. None of these compounds interfered with the analytes (57,58). 

In addition to the mobile phase composition, the effect of other parameters such as temperature, flow rate, pH, and structure of the analytes were also studied, but only a few reports were available in the literature. In 1995, Lin and Maddox [66] studied the effect of temperature on the chiral resolution of amino acids and esters. The temperature was varied from 5°C to 25°C and it was reported that the resolution improved at low temperature. Hyun et al. [48-50,67] carried out the effect of temperature on the chiral resolution of amino alcohols, amines, fluoroquinolones, and other drugs. Again, lowering of temperature resulted in better resolution. The effect of temperature on the chiral resolution of phenylalanine, phenylglycine, and 2-hydroxy-2-(4-hydroxy-phenyl)-ethyl amine is shown in Table 5 [50], which indicates an increase in retention factors at lower temperature, but the best separation occurred at 20°C. These experiments indicated the exothermic nature of chiral resolution on CCE-based CSPs. Lin and Maddox [66] also studied the effect of flow rate on the chiral resolution of... 

Analytical Properties a-Cyclodextrin (cyclohexamolyose) reverse phase separation of barbiturates and other drugs, and aromatic amino acids the substrate is composed of six glucose units and has a relative molecular mass of 972 the cavity diameter is 0.57 nm, and the substrate has a water solubility of 14.5 g/ml Reference 13-28... 

Several LC-MS and LC-MS/MS methods were developed in plasma for only one antidepressant and, sometimes, its major metabolite(s) to perform pharmacokinetic, bioavailability, or bioequivalence studies. Analytical methods developed for these purposes require very low LLOQ values and, usually, narrow linear ranges covering the low range of the therapeutic concentrations are validated. In this context, several methodologies were described for the determination of fluoxetine [94, 95, 98-100], paroxetine [44, 71, 85, 101, 102], venlafaxine [48, 61, 64, 86, 103,104], sertraline [62, 68, 83], citalopram [46, 89] and escitalopram [105], mianserine [106, 107], mirtazapine [42], trazodone [84], nefazodone [51, 81], duloxetine [47, 50, 73], and bupropion [43], Deuterated analogues of the analyte of interest or of other drugs were employed by few authors as IS [43, 61, 73, 81, 85, 99] however, in most of these methods, another antidepressant or other therapeutic drug was used for this purpose. 

The major advantage of (fractional) oral clearance as a phenotypic trait is that its value is linearly related to the enzyme s catalytic activity, provided that first-order conditions are present. This requirement, along with any safety considerations, is the main reason the dose of an in vivo probe should be as low as possible, consistent with analytical considerations. Furthermore, it is possible to directly extrapolate this type of trait measure to the disposition of other drugs whose metabolism is mediated by the measured enzyme and also to place the trait value within a therapeutic context. On the other hand, estimation of oral clearance requires multiple blood and urine collections, often over many hours, that are an inconvenience for the study subject and require considerable amounts of analytical time and effort. Because of this, simpler and less time-consuming approaches have often been used. However, it is not always appreciated that such phenotyping tests provide only an indirect measure of metabolizing activity and may be affected by factors other than the enzyme s intrinsic clearance. In addition, it is difficult to relate an indirect trait measure to parameters that are of clinical importance, such as the drug s clearance. 

NMR is a ubiquitous and indispensable tool for elucidating molecular structures, determining impurities, and studying molecular dynamics. NMR is also used to analyze simple mixtures without physical separation, and to measure molecular properties and bulk properties of the medium. The nondestructive nature of NMR permits the sample to be used for further investigation. As a noninvasive technique, NMR is often used to study molecular binding and to screen potential drug candidates. Therefore, despite its low sensitivity, NMR has become an essential analytical tool in academic and industrial environments. However, the inherent insensitivity causes detection limits of NMR to be a few orders below that of other standard analytical techniques [14], At present, the limit of detection achieved by NMR in concentration terms is in the millimolar range. 

Other drugs, including nicotine, have been investigated in nonhead hair samples. However, the data (Table 5) are of less significance since all the analyses but one lack specificity due to the analytical methods used. The highest concentrations were observed sometimes in axillary hair (phenobarbital, zipeprol, nicotine), sometimes in pubic hair for benzodiazepines. No correlation between concentrations in hair samples and blood or urine have been reported. Nevertheless, these data have the merit to demonstrate that nonhead hair specimens could represent an alternative to head hair when the latter is not available for the detection of drugs. 

The following postmortem concentrations of dexbrompheniramine were reported in a fatality involving the ingestion of dexbrompheniramine and 3 other drugs blood 0.2 4.g/ml, liver 4.5 Ag/g (R. C. Baselt and E. M. Gross,/, analyt. Toxicol., 1977,1, 168-170). 

Other drugs (mainly diazepam, methadone or morphine) were detected in all subjects except one in which the cause of death was multiple stab wounds (D. M. Chmnet al., J. analyt. Toxicol., 1979,3, 143-149). 

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