Biological fluids drugs

When nano LC is combined with mass spectrometer detection, attamole detection can be achieved for low abundance components in biological fluids, drug metabolites, and natural products such as Chinese herb medicines. Nano LC-MS-MS has become an essential tool for complex biological and drug metabolite studies. Nano LC-MS presents two significant differences from conventional analytical HPLC (1) large enhancement factor for sample detection and (2) direct interface to MS without flow splitting. The enhancement in MS ion counts relative to a conventional 4.6 mm ID column is proportional to the ratio of the square of the column diameter ... 

J. Chamberlain, Mnalysis of Drugs in Biological Fluids, CRC Press, Boca Raton, Fla., 1985. 

The aromatic portion of the molecules discussed in this chapter is frequently, if not always, an essential contributor to the intensity of their pharmacological action. It is, however, usually the aliphatic portion that determines the nature of that action. Thus it is a common observation in the practice Ilf medicinal chemistry that optimization of potency in these drug classes requires careful attention to the correct spatial orientation of the functional groups, their overall electronic densities, and the contribution that they make to the molecule s solubility in biological fluids. These factors are most conveniently adjusted by altering the substituents on the aromatic ring. 

J. V. Posluszny and R. Weinherger, Detemiination of drug substances in biological fluids by diiect injection multidimensional liquid chromatography with a micellar cleanup and reversed-phase clnomatography , Chem. 60 1953-1958(1988). 

The dense fluid that exists above the critical temperature and pressure of a substance is called a supercritical fluid. It may be so dense that, although it is formally a gas, it is as dense as a liquid phase and can act as a solvent for liquids and solids. Supercritical carbon dioxide, for instance, can dissolve organic compounds. It is used to remove caffeine from coffee beans, to separate drugs from biological fluids for later analysis, and to extract perfumes from flowers and phytochemicals from herbs. The use of supercritical carbon dioxide avoids contamination with potentially harmful solvents and allows rapid extraction on account of the high mobility of the molecules through the fluid. Supercritical hydrocarbons are used to dissolve coal and separate it from ash, and they have been proposed for extracting oil from oil-rich tar sands. 

Figure 8.10 General scheme for the isolation of drugs from biological fluids.

An internal standard method gives more reliable results when elaborate sample preparation is required, as in extraction of a drug substance from biological fluids, or extraction of pesticides and herbicides from soil and plant matter. The addition of internal standard (IS) to the sample and standard acts as a marker to give accurate values of the recovery of the desired compound(s). Since the determination of wt% involves the ratio of the detector responses in the two chromatograms, the injection volume is not critical as in an external standard method. 

Ibrahim et al. [30] described a fluorimetric method for the determination primaquine and two other aminoquinoline antimalarial drugs using eosin. Powdered tablets or ampule contents containing the equivalent of 50 mg of the drug was extracted with or dissolved in water (100 mL). A 10 mL aliquot was mixed with 10 mL of aqueous ammonia, 1 mL of 0.001% eosin (C.I. acid red 87) in dichloro-ethane, and dichloroethane was added to volume. Primaquine was determined fluorimetrically at 450 nm (excitation at 368 nm). Calibration graphs were rectilinear for 0.1-5 pg/mL of primaquine. Recoveries were quantitative. The method could be readily adapted for determination of the drug in biological fluids. 

Phosphates are often poor drug candidates29 due to their instability in biological fluids and inability to penetrate cell membranes. As a result, we focused our efforts on the discovery of suitable phosphate mimics. In these studies we evaluated various analogs with well-known phosphate replacements (Figure 4), namely phosphonate (3), sulfate (4), carboxylate (5) and dicarboxylate (6). 

Determination in Biological Fluids and Tissues All the advances in pharmacokinetics and drug metabolism described in Sections 7 and 8 would not have been possible without the availability of the proper analytical methods. The following is a tabulation of publications in this field, most of which have already been discussed in Section 5. It should be mentioned that a few publications talk about aspirin blood levels, but really mean salicylate levels. The following tabulation covers only those papers where aspirin was differentiated from other salicylates by chromatography or other means. It seems that the "workhorse" for serum salicylate levels is still the colorimetric (ferric-nitrate) method of Brodie, Udenfriend and Coburn153 published in 1944, or modifications thereof. Simplified versions (cf. 206) may lead to erroneous results under certain conditions.207 The method is also applicable for urinary metabolites after proper hydrolysis (cf. 208). For other methods restricted to salicylic acid, see Section 5.61. 

J.E. Fairbrother in "Assay of Drugs and Other Trace Compounds in Biological Fluids, Ed. by E. Reid, "Methodological Developments in Biochemistry, Vol. 5, Longman Group, London, 1976, p. 141. 

The first spectrofluorimetric methods reported for the determination of nalidixic acid and its metabolites in biological fluids did not differentiate between nalidixic acid and hydroxynalidixic acid. The determination of free nalidixic acid and the hydroxy-metabolite in human urine plasma and feces was performed by extraction by toluene from acidified biological fluid and subsequent fluorimetric measurement at 325/375 nm of sample re-extracted into aqueous solution.(8) Conjugated nalidixic and hydroxynalidixic acids were determined by acid hydrolysis and then toluene extraction for fluorimetric measurement of the total drug. The conjugated nalidixic acid was then determined by difference. 

Schellen A. et al., 2003. Generic solid phase extraction-liquid chromatography-tandem mass spectrometry method for fast determination of drugs in biological fluids. J Chromatogr B 788 251. 

---