Highly sensitive determination of cimetidine and its metabolites in serum and urine by high-performance liquid chromatography

An Overview of Analytical Determination of Diltiazem, Cimetidine, Ranitidine, and Famotidine by UV Spectrophotometry and HPLC Technique

This review article recapitulates the analytical methods for the quantitative determinations of diltiazem and three H2receptor antagonists (cimetidine, ranitidine, and famotidine) by one of the spectroscopic technique (UV spectrophotometery) and separation technique such as high-performance liquid chromatography (HPLC). The clinical and pharmaceutical analysis of these drugs requires effective analytical procedures for quality control, pharmaceutical dosage formulations, and biological fluids. An extensive survey of the literature published in various analytical and pharmaceutical chemistry-related journals has been compiled in its review. A synopsis of reported spectrophotometric and high-performance liquid chromatographic methods for individual drug is integrated. This appraisal illustrates that majority of the HPLC methods reviewed are based on the quantitative analysis of drugs in biological fluids, and they are appropriate for therapeutic drug monitoring purpose.

Simple and universal HPLC-UV method to determine cimetidine, ranitidine, famotidine and nizatidine in urine: application to the analysis of ranitidine and its metabolites in human volunteers

A validated, simple and universal HPLC-UV method for the determination of cimetidine, famotidine, nizatidine and ranitidine in human urine is presented. This is the first single HPLC method reported for the analysis of all four H(2) antagonists in human biological samples. This method was also utilized for the analysis of ranitidine and its metabolites in human urine. All calibration curves showed good linear regression (r(2)>0.9960) within test ranges. The method showed good precision and accuracy with overall intra- and inter-day variations of 0.2-13.6% and 0.2-12.1%, respectively. Separation of ranitidine and its metabolites using this assay provided significantly improved resolution, precision and accuracy compared to previously reported methods. The assay was successfully applied to a human volunteer study using ranitidine as the model compound.

Sensitive determination of G-protein-coupled receptor binding ligands by solid phase extraction–electrospray ionization–mass spectrometry

High affinity Histamine H2-receptor binding ligands were assayed by automated solid phase extraction (SPE) coupled via electrospray ionization with a Quadrupole-Time-of-Flight mass spectrometer (Q-ToF-MS). The mass spectrometric behavior of these analytes was tested in aqueous solutions with several (nine) volatile salts, in different pH, and with various methanol contents. Out of the high amount of available ligands, three fluorescent-labeled molecules (5706, 5707, and 5708) were studied in detail. The limits of detection (LODs) for all three compounds obtained in mass spectrometric detection was 1 fmol (absolute) in continuous flow and FIA (flow injection analysis) measurements. The results obtained with FIA-fluorescence detection gave LODs a factor 10-100 times higher. A systematic investigation of sample solving conditions, loading flow conditions, and elution flow conditions made the automated SPE-MS coupling efficient. Ideally, the ligands were dissolved in MeOH-25 mM phosphate buffer (30:70 v/v; pH 11), the SPE loading flow comprised MeOH-25 mM phosphate buffer (30:70 v/v; pH 11) and the SPE elution flow contained MeOH-100 mM ammonium formate solution (90:10 v/v; pH 3). Using this method on a C18-modified silica cartridge (C18, 5 microm, 100 A, 300 microm i.d. x 5 mm, LC Packings) assures high recovery and achieved LODs for all three compounds of 5 fmol (absolute). As an absolute amount of ligands specifically bound on H2-receptors in biochemical experiments is, as will be published elsewhere, between 10 and 100 fmol, the SPE-MS method for the basic compounds can be directly applied for these Histamine H2-receptors.

Spectrophotometric determination of cimetidine in pharmaceuticals and urine using batch and flow-injection methods

Two sensitive and fast spectrophotometric methods using batch and flow-injection procedures for the determination of cimetidine (CMT) are proposed. The methods are based on the formation of a green complex between this drug and Cu(II) in acetic/acetate medium of pH 5.9. The calibration graphs resulting from measuring the absorbance at 330 nm are linear over the ranges 2.5 x 10(-6)-1.0 x 10(-3) and 5 x 10(-6)-2.0 x 10(-3) M with detection limits of 9.5 x 10(-7) and 2.1 x 10(-6) for batch and flow-injection methods, respectively. The methods are applied to the routine analysis of CMT in pharmaceuticals and human urine.

Quantitative analysis of cimetidine in human plasma using LC/APCI/SRM/MS

A quantitative method was developed and validated for rapid and sensitive analysis of cimetidine in human plasma. The method involved the use of liquid chromatography (LC) coupled with atmospheric pressure chemical ionization (APCI) and selected reaction monitoring (SRM) mass spectrometry (MS). A cimetidine analog, SKF92374, was used as the internal standard. Separation of cimetidine and the internal standard was accomplished using a reverse-phase HPLC column (C18). The eluted components were ionized by the APCI source and subsequently detected by a highly selective triple quadrupole mass spectrometer in the SRM mode. Linear standard curves were obtained from 5 ng/mL (lower limit of quantitation) to 10,000 ng/mL. The results demonstrated excellent precision (%RSD 1. 1-8.9%) and accuracy (94.7-108.0%) over this range. In addition, the amount of plasma sample needed for analysis was small (50 muL), and the plasma pretreatment (analyte recovery >94%) was simple and time saving. This assay was used to evaluate cimetidine levels in premature infants following intravenous infusion of cimetidine.

Determination of ebrotidine and its metabolites in human urine by reversed-phase ion-pair high-performance liquid chromatography

Ebrotidine is a new H2-receptor antagonist with powerful antisecretory activity, demonstrated gastroprotection and the ability to inhibit protease and lipase activities of Helicobacter pylori. As a tool in the clinical pharmacokinetic study of ebrotidine, an analytical method for the simultaneous determination of ebrotidine an its metabolites in human urine was developed. An ion-pair reversed-phase HPLC separation using 1-hexanesulfonic acid and acetonitrile as mobile phase with gradient elution was optimized. In addition, several procedures of preconcentration and clean-up were tested, including solid-phase and liquid-liquid extraction, the mixture dichloromethane-2-propanol (9:1, v/v) at pH 11 being the most efficient. The quality parameters of the whole analytical method were established, the calibration curves were linear over the range studied (1-200 micrograms/ml) and the reproducibility of the method was high (inter-day R.S.D. values lower than 4.4%). The limits of detection were between 26 and 110 ng/ml of urine for ebrotidine and its metabolites. The method was applied to the analysis of urine collected from two volunteers during 96 h following oral administration of ebrotidine at a dose of 400 mg.

Accurate measurement of impaired glomerular filtration using single-dose oral cimetidine

To improve the validity of a timed creatinine clearance as a measure of glomerular filtration rate (GFR), we investigated whether a single 800-mg dose of oral cimetidine was sufficient to inhibit tubular secretion of creatinine (TScr). Forty-five 3-hour timed creatinine clearances (Clcr) with single 800-mg dose oral cimetidine (TCC) in 17 renal transplant recipients with marked renal function impairment (creatinine 2.0 to 7.1 mg/dL) were compared with simultaneous [125I]-iothalamate GFR (Cliothal). For comparison, 13 timed Clcr without cimetidine (TC), and 36 24-hour Clcr were performed. The TCC was the most accurate: the ratio (mean +/- SD) of TCC:Cliothal was 1.12 +/- 0.02, compared with 1.33 +/- 0.08 for Clcr:Cliothal and 1.53 +/- 1.02 for TC:Cliothal. The difference between Cliothal and TCC was small over the range of GFRs tested (mean +/- 2 SD), 0.9 +/- 2.5 mL/min/1.73 m2. The intraclass correlation (R) for within-subject reproducibility of the TCC in five subjects was 0.8 (95 percent CI; 0.5, 0.9), and in 11 subjects who had at least three GFR determinations over 24 weeks, the TCC was as responsive to change in GFR as Cliothal. There was an inverse relationship between fractional excretion of cimetidine and GFR (r2 = -0.70), suggesting increased tubular secretion of cimetidine with decreasing GFR. In conclusion, a single 800-mg oral dose of cimetidine was effective in inhibiting TScr such that the TCC was an accurate, reproducible, and responsive test of GFR.

Ferrous sulfate does not reduce serum levels of famotidine or cimetidine after concurrent ingestion

A series of randomized crossover studies were performed to determine whether there was a reduction in serum levels of cimetidine and famotidine when coingested with ferrous sulfate (300 mg). Coingestion of a ferrous sulfate tablet with cimetidine (300 mg) was associated with little reduction in serum cimetidine area under the curve (AUC) (mean versus mean, 20.8 versus 23.4 mumol.hr/L; mean percentage difference, -11%; 95% confidence interval [CI] of percentage difference, -26% to 4.2%) or peak concentration (Cmax) (mean versus mean, 5.1 versus 6.1 mumol/L; mean percentage difference, -16%; CI of percentage difference, -36% to 4%). Similarly, ferrous sulfate solution coingested with cimetidine caused little change in cimetidine AUC (mean versus mean, 19.9 versus 23.0 mumol.hr/L; mean percentage difference, -13%; CI of percentage difference, -34% to 7%) or Cmax (mean versus mean, 5.0 versus 5.0 mumol/L; mean percentage difference, 1%; CI of percentage difference, -18% to 20%). Concurrent ingestion of famotidine (40 mg) with a ferrous sulfate tablet did not result in significant reductions in serum famotidine AUC (mean versus mean, 1.78 versus 1.99 mumol.hr/L; mean percentage difference, -10%; CI of percentage difference, -34% to 13%) or Cmax (mean versus mean, 0.31 versus 0.32 mumol/L; mean percentage difference, -3%; CI of percentage difference, -27% to 22%). The formation of famotidine:iron(III) complexes was shown in methanol but was not observed in an aqueous buffer at pH 6.5. Ranitidine did not bind iron in an aqueous buffer and only weakly bound iron in methanol. Coingestion of ferrous sulfate with either cimetidine or famotidine does not cause a clinically relevant reduction in serum histamine H2-receptor blocker levels and, on the basis of in vitro binding experiments, iron is unlikely to interact with ranitidine.

Ion-pair solid-phase extraction of cimetidine from plasma and subsequent analysis by high-performance liquid chromatography

An improved method is described for the solid-phase extraction of cimetidine from plasma or serum with subsequent analysis by HPLC. New aspects of the method include protein precipitation with metaphosphoric acid (5%, w/v), followed by selective adsorption of cimetidine and the internal standard ranitidine on the surface of a solid-phase phenyl (PH Bond Elut) column, using octanesulfonate as an ion-pairing agent. Separation was achieved on a LiChrosorb RP-18 column with a mobile phase consisting of acetonitrile-0.01 M phosphate buffer pH 3.0 containing 0.005 M octanesulfonate (22:78, v/v). The intra-assay coefficient of variation varied between 0.7 and 4.0%. The procedure provides cleaner and more stable samples and a better recovery (90 +/- 2.3%) and sensitivity (limit of detection 5 ng/ml and limit of quantitation 25 ng/ml) as compared with previous methods.

Solid-phase extraction of small drugs on apolar and ion-exchanging silica bonded phases: towards the development of a general strategy

In connection with the development of a general strategy for solid-phase extraction (SPE) of drugs, the use of the apolar octadecyl silica bonded phase and ion-exchanging phases with a benzene sulphonic acid or quaternary amine bonded functionality is investigated for the SPE of small polar drugs. This investigation was performed on a set of 15 drugs, belonging to varying pharmacological groups and with varying structures. For each analyte, its adsorption on the C18 and the ion-exchanging phase was controlled for an aqueous solution and for a spiked plasma sample. For those analytes retained on the sorbent, different elution solvents were compared. Although SPE methods could successfully be developed for some drugs, no general solution can be proposed and no solution was found for a few drugs. The main problems are that for these few drugs no sufficient retention is obtained on any SPE phase investigated or the selectivity is too low.

Electrochromatographic solid-phase extraction for determination of cimetidine in serum by micellar electrokinetic capillary chromatography

A highly effective electrochromatographic solid-phase extraction and preconcentration method is reported for the determination of cimetidine in serum in the concentration range 0.233-11.4 micrograms/ml. Preconcentrated samples were determined by micellar electrokinetic capillary chromatography while ranitidine was used as an internal standard. Sample preparation included retention of the analyte on a C18 solid-phase cartridge, followed by elution assisted by an applied voltage of 150 V. From 0.5-ml serum samples, 20-50-microliters aliquots were collected for electrophoretic analysis. Within the studied concentration range, the method was linear and provided adequate precision.