Simultaneous determination of triamterene and hydrochlorothiazide in tablets using derivative spectrophotometry

A quick and accurate method for determining triamterene and hydrochlorothiazide in complex drugs of diuretic activity by using first-derivative (D1) and second-derivative (D2) spectrophotometry was developed. The zero-crossing technique was employed in measurements, using D1 at lambda = 240.9 nm and D2 at lambda= 278.2 nm for determining triamterene and D1 at lambda = 255.7 nm and D2 at lambda = 283.2 nm for hydrochlorothiazide. The linear relationship between the values of derivatives and analyte concentrations are maintained for concentrations from 2.40 microg x mL(-1) to 12.00 microg x mL(-1) for triamterene and from 1.25 microg x mL(-1) to 6.25 microg x mL(-1) for hydrochlorothiazide. LOD for triamterene was 0.90 microg x mL(-1) or 1.02 microg x mL(-1), while LOQ was 2.73 microg x mL(-1) or 3.08 microg x mL(-1). The corresponding values for hydrochlorothiazide were: LOD 0.25 microg x mL(-1) or 0.17 microg x mL(-1) and LOQ 0.77 microg x mL(-1) or 0.51 microg x mL(-1) depending on the derivative used. The determination results of drug constituents are of high accuracy, percentage recovery ranging from 97.17% to 99.74% for triamterene and from 102.44% to 102.64% for hydrochlorothiazide, and good precision. The computed values of RSD are smaller than 2.73% for triamterene and below 1.63% for hydrochlorothiazide. Selectivity and sensitivity of the developed method are satisfactory.     

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.     

The effects of interacting variables on the tensile strength, disintegration and dissolution of paracetamol tablets

A factorially designed scheme has been used to analyse the separate and combined effects of packing fraction (P), nature of binder (N) and concentration of binder (C) on the tensile strength, disintegration and dissolution (t50%) times of paracetamol tablets. In general, P has the greatest effect on tensile strength, disintegration and dissolution times followed by C then N. For the variables in combination, the ranking of the effects on tensile strength, for the PVP/gelatin formulations, are P x N greater than N x C greater than P x C and for the PVP/tapioca formulations are P x C = N x C greater than P x N. For disintegration and for dissolution, the ranking for the PVP/gelatin formulations are P x C greater than P x N = N x C and P x N greater than P x C greater than N x C, respectively, and for the PVP/tapioca formulations are P x N greater than N x C = P x C. The results also show that tapioca acts as a binding agent when included in paracetamol tablet formulations, but it is a weaker binder than either PVP or gelatin. It is thus required in a higher concentration to produce tablets of comparable physical properties with those formulated with PVP or gelatin.     

Absolute rate constants for the reaction of hypochlorous acid with protein side chains and peptide bonds

Hypochlorous acid (HOCl) is a potent oxidant, which is produced in vivo by activated phagocytes. This compound is an important antibacterial agent, but excessive or misplaced production has been implicated in a number of human diseases, including atherosclerosis, arthritis, and some cancers. Proteins are major targets for this oxidant, and such reaction results in side-chain modification, backbone fragmentation, and cross-linking. Despite a wealth of qualitative data for such reactions, little absolute kinetic data is available to rationalize the in vitro and in vivo data. In this study, absolute second-order rate constants for the reactions of HOCl with protein side chains, model compounds, and backbone amide (peptide) bonds have been determined at physiological pH values. The reactivity of HOCl with potential reactive sites in proteins is summarized by the series: Met (3.8 x 10(7) M(-1) x s(-1)) > Cys (3.0 x 10(7) M(-1) x s(-1)) > cystine (1.6 x 10(5) M(-1) x s(-1)) approximately His (1.0 x 10(5) M(-1) x s(-1)) approximately alpha-amino (1.0 x 10(5) M(-1) x s(-1)) > Trp (1.1 x 10(4) M(-1) x s(-1)) > Lys (5.0 x 10(3) M(-1) x s(-1)) > Tyr (44 M(-1) x s(-1)) approximately Arg (26 M(-1) x s(-1)) > backbone amides (10-10(-3) M(-1) x s(-1)) > Gln(0.03 M(-1) x s(-1)) approximately Asn (0.03 M(-1) x s(-1)). The rate constants for reaction of HOCl with backbone amides (peptide bonds) vary by 4 orders of magnitude with uncharged peptide bonds reacting more readily with HOCl than those in a charged environment. These kinetic parameters have been used in computer modeling of the reactions of HOCl with human serum albumin, apolipoprotein-A1 and free amino acids in plasma at different molar excesses. These models are useful tools for predicting, and reconciling, experimental data obtained in HOCl-induced oxidations and allow estimations to be made as to the flux of HOCl to which proteins are exposed in vivo.     

Voltammetric behavior of cefixime and cefpodoxime proxetil and determination in pharmaceutical formulations and urine

Electrochemical reduction behavior of cephalosporins, Cefixime (CF) and Cefpodoxime Proxetil (CP) have been studied by using different voltammetric techniques in Britton-Robinson buffer system. Two well defined cathodic waves are observed for both the compounds in the entire pH range. Number of electrons transferred in the reduction process was calculated and the reduction mechanism is proposed. The results indicate that the process of both the compounds is irreversible and diffusion-controlled. The peak currents for CF and CP are found to be linear over the range of concentration 6.0 x 10(-8) to 1.2 x 10(-5) mol l(-1) and 8.8 x 10(-8) to 1.1 x 10(-5) mol l(-1), respectively. The lower detection limits are found to be 4.6 x 10(-8) and 8.52 x 10(-8) mol l(-1) for the two compounds. A differential pulse voltammetric method has been developed for the determination of these drugs in pharmaceutical formulations and urine samples.     

Acute toxicity of TBT and IRGAROL in Artemia salina

A 24-hour LC(50) bioassay method was carried out to study acute toxicity of Tributyltin (TBT) and IRGAROL (C(11)H(19)N(5)S) in Artemia salina. Five graded levels of both biocides were tested. According to the range test, the doses of TBT were 11.6 ng x l(-1), 21.0 ng x l(-1), 37.3 ng x l(-1), 65.2 ng x l(-1), and 116.5 ng x l(-1), and for IRGAROL were 1.0 mg x l(-1), 1.8 mg x l(-1), 3.2 mg x l(-1), 5.6 mg x l(-1), and 10 mg x l(-1). The determined LC(50) values were 41.41 ng x l(-1) and 1.62 mg x l(-1) respectively. These results indicate that in this system TBT is acutely more toxic than IRGAROL; however, both are proven environmentally toxic substances.     

A primary culture system of postnatal rat heart cells for the study of cocaine and methamphetamine toxicity.

It is now well documented that both cocaine (Coc) and methamphetamine (Meth) are independently capable of inducing injurious effects on the adult and developing myocardium. In addition, when these drugs are used concomitantly such as in polydrug abuse, it has been suggested that they may cause synergistic adverse effects on the myocardium. In this investigation, primary myocardial cell cultures were established from 3-5-day-old Sprague-Dawley rats to describe the adverse effects of Coc and Meth on the myocardium. After the cells were in culture for 4 days, they were exposed to 1 x 10(-5) and 1 x 10(-3) M Coc alone; 1 x 10(-5) and 1 x 10(-3) M Meth alone; and combinations of 1 x 10(-3) M Coc with 1 x 10(-5) M Meth and 1 x 10(-5) M Coc with 1 x 10(-5) M Meth. Lactate dehydrogenase (LDH) release, morphology, and beating activity were evaluated after exposure to the drugs for 1, 4 and 24 h. With all treatment groups for the first 4 h, LDH release was not significantly different from untreated controls. Significant LDH release (P less than 0.001) was exhibited at 24 h with 1 x 10(-3) M Coc alone, 1 x 10(-3) M Meth alone, and 1 x 10(-3) M Coc with 1 x 10(-5) M Meth. For 24 h of treatment, cellular injury (pseudopodia, vacuolization, granulation) induced by 1 x 10(-3) M and 1 x 10(-5) M Coc alone was extensive and minimal, respectively. When 1 x 10(-5) M Meth was added with 1 x 10(-5) M Coc, pseudopodia formation was extensive. No measurable beating activity was observed at 1, 4 and 24 h exposure to 1 x 10(-3) M Coc alone and 1 x 10(-3) M Coc with 1 x 10(-5) M Meth. At 1 h, beating activity after treatment with 1 x 10(-5) M Coc alone and 1 x 10(-5) M Meth alone was not significantly different from untreated controls; however, the percentage of areas exhibiting contractile activity was depressed. Addition of Meth (1 x 10(-5) M) potentiated Coc-induced (1 x 10(-5) M) depression of contractile activity at all 3 time-points. These data suggest that Coc and Meth may interact synergistically at the cellular level to directly potentiate injury to postnatal myocardial cell cultures.     

Assaying all of the nitrogen oxides in breath modifies the interpretation of exhaled nitric oxide

Exhaled nitric oxide (NO) assays measure the quantity of NO that emanates from the airway, not the amount of NO that is formed. Consumptive processes-including oxidation reactions-decrease the amount of gas phase NO available for exhalation. Higher oxides of nitrogen (HiNO(x)) are resulting reaction products, and are easily measured in exhaled breath condensate (EBC). We performed concurrent sampling of exhaled breath for gas phase NO and EBC HiNO(x) in controls and stable asthmatics. We identified that, mole for mole, asthma patients hourly exhale more HiNO(x) than they do NO, with a HiNO(x)/NO ratio of 1.21 (0.54-3.4). This is the reverse of the ratio found in controls, in whom the HiNO(x)/NO ratio was 0.75 (0.44-0.93), p=0.04. The sum of the hourly molar exhalation of NO and HiNO(x) was significantly higher in asthmatics (333 nmol/h (221-543) than controls (179 (138-231), p<0.001). We conclude that exhaled oxides of nitrogen are more informative when measured together as opposed to in isolation. We suggest that inflammation can be better evaluated with HiNO(x) and NO measured concurrently, and that the level of oxidation in the lung can be evaluated by comparing the easily measured ratios of HiNO(x) to NO in the exhaled breath.     

PVC membrane ion-selective electrodes for the determination of Hyoscyamine in pure solution and in pharmaceutical preparations under batch and flow modes

New PVC membrane electrodes selective for the determination of hyoscyamine ion (Hy(+)) based on hyoscyamine tetraphenylborate (Hy-TPB) or hyoscyamine phosphotungstate (Hy-PT) ion-exchangers as electroactive materials are described. The electrodes show a linear response for Hy(+) over the concentration range of 1.00 x 10(-5) to 1.26 x 10(-2) mol L(-1) and 1.00 x 10(-4) to 1.00 x 10(-2) mol L(-1) in case of Hy-TPB electrode applying batch and flow injection analysis (FIA), respectively, and 1.00 x 10(-5) to 4.52 x 10(-3) mol L(-1) and 6.31 x 10(-5) to 1.00 x 10(-2) mol L(-1) in case of Hy-PT electrode for batch and FIA, respectively. The lower detection limits are 3.90 x 10(-6) and 4.51 x 10(-6) at 25 degrees C for Hy-TPB and Hy-PT electrodes, respectively. The electrodes posses near Nernstian slopes of 56.5 and 57.8 mV/decade for Hy-TPB and Hy-PT electrodes, respectively, and a fast potential response of < or =20 s which is almost constant over a pH range of 3-10. Selectivity coefficient data for some common inorganic cations, sugars, amino acids and the components, other than hyoscyamine, of the mixed drugs investigated show negligible interference. The electrodes have been applied to the potentiometric determination of hyoscyamine in pure solution and in pharmaceutical preparations under batch and FIA conditions and as end point indicator electrode for the determination of hyoscyanine using potentiometric titration. For the concentrations (1.08 x 10(-5) mol L(-1) to 3.16 x 10(-3) mol L(-1)) an average recovery of 99.95% with relative standard deviation of 0.63% has been achieved. The effect of temperature on the electrodes was also studied.     

Overlap in the pharmacology of L-type Ca2+-channel blockers and 5-HT2 receptor antagonists in rat aorta.

We have previously shown that elimination of buffer Ca2+ markedly reduced maximum 5-HT-induced contractions. We have now investigated the effect of L-type Ca2+-channel blockers and 5-HT2 receptor antagonists on 5-HT- and K+-induced contractions in rat aorta to explore the possibility of a relationship between blockade of L-type Ca2+ channels and 5-HT2 receptor antagonism. Sodium nitroprusside, felodipine, nifedipine, diltiazem, cinnarizine, verapamil, ritanserin, cyproheptadine, ketanserin and mianserin inhibited 5-HT-induced contractions of rat aorta with mean IC50 values (concentration (M) resulting in 50% inhibition) of 2.2 x 10(-11), 6.6 x 10(-11), 1.5 x 10(-9), 1.7 x 10(-9), 3.2 x 10(-7), 5.4 x 10(-7), 9.7 x 10(-10), 1.9 x 10(-8), 5.0 x 10(-7) and 6.4 x 10(-7), respectively. The same compounds antagonized K+-induced rat aortic contractions with the rank order of potency (mean IC50, M): felodipine (7.0 x 10(-11)) > nifedipine (4.8 x 10(-9)) > sodium nitroprusside (4.1 x 10(-8)) > verapamil (5.5 x 10(-8)) > cyproheptadine (6.2 x 10(-8)) > diltiazem (4.1 x 10(-7)) > cinnarizine (1.3 x 10(-6)) > ritanserin (1.8 x 10(-6)) > ketanserin (9.0 x 10(-6)) > mianserin (2.0 x 10(-5)). These data are indicative of a highly significant correlation (r=0.81, P=0.03) between potency against 5-HT-induced contraction and that against contractile response to K+ depolarization, and suggest overlap of the pharmacology of L-type Ca2+-channel blockers and 5-HT2 receptor antagonists in rat aorta.     

丁苄腈心安与心得安对大鼠心肌β肾上腺素受体亲和力比较

本文以~3H双氢心得舒(~3H—DHA)作为放射性配基,测定大鼠心肌上β肾上腺素受体的最大结合容量(B_(max))和平衡解离常数(K_D)分别为104.1±4.7fmol/mg蛋白质及10.1±2.7nM,Hill系数(nH)为1.007±0.002。丁苄腈心安和心得安对大白鼠心肌β肾上腺素能受体与~3H-DHA结合的半数抑制浓度(IC_(50))分别为3.30±0.74×10~(-8)M和3.87±0.66×10~(-7)M,表观解离常数各为2.20±0.49×10~(-8)及2.58±0.44×10~(-7)。故丁苄腈心得安对大鼠心肌β肾上腺素受体的亲和力约为心得安的11.7倍。     

Effects of CKD-602, a new camptothecin anticancer agent, on pregnant does and embryo-fetal development in rabbits

CKD-602 is a newly developed camptothecin anticancer agent. Preclinical studies suggest that it may have greater antitumor activity and lower toxicity than other camptothecin anticancer agents. The potential of CKD-602 to induce developmental toxicity was investigated in the New Zealand White rabbit. Seventy-two artificially inseminated females (artificial insemination=day 0) were distributed among three treatment groups and a control group. CKD-602 was at dose levels of 0, 0.024, 0.048, or 0.096 mg x kg(-1) x day(-1) administered intravenously to pregnant does from days 6 to 18 of gestation. All does were subjected to caesarean section on day 28 of gestation. At 0.096 mg x kg(-1) x day(-1), 2 cases of abortion and 3 cases of death in pregnant rabbits were found in late gestation. In addition, an increase in the embryonic resorptions and a decrease in the litter size were found. At 0.048 mg x kg(-1) x day(-1), a single doe aborted on gestational day 26. An increase in the embryonic resorptions and fetal morphological alterations and a decrease in the litter size were also found. There were no signs of maternal toxicity or developmental toxicity at 0.024 mg x kg(-1) x day(-1). The results show that 13-day repeated intravenous dose of CKD-602 during the major organogenetic period in rabbits produces increased incidence of abortion and death, increased number of embryonic resorptions and fetal morphological alterations, and decreased litter size at dose levels of above 0.048 mg x kg(-1) x day(-1). In the current experimental conditions, the no-observed-adverse-effect levels (NOAELs) of CKD-602 are considered to be 0.048 mg x kg(-1) x day(-1) for does and 0.024 mg x kg(-1) x day(-1) for embryo-fetal development.     

Functionalized S-thio-di- and S-oligosaccharide precursors as templates for novel SLex/a mimetic antimetastatic agents

Adhesive interactions between molecules expressed on vascular endothelium and circulating tumor cells are key early events in cancer metastasis. Best characterized to date is the selectin family of cell adhesion molecules, which can bind to and stabilize blood-borne cells on organ vasculature, facilitating the cell-cell and cell-substratum interactions leading to tumor seeding and proliferation. Major ligands of E-selectin, the selectin family member expressed on vascular endothelial cells, include sialylated, fucosylated glycans such as Sialyl Lewis type carbohydrate complexes (SLe(x) and SLe(a)). These carbohydrate antigens are ubiquitously expressed on tumor cells with high metastatic potential, including colon and pancreatic carcinomas, and have been found to selectively and avidly bind E-selectin. Compounds that prevent E-selectin-SLe(x/a)binding represent an attractive tool in the prevention of cancer dissemination. Review of preclinical in vitro and in vivo studies suggest that SLe(x/a) 'mimetics' may serve as a potent class of anti-metastatic compounds. These agents are designed to outcompete SLe(x/a) antigens expressed on tumor cell surfaces to prevent initial vascular adhesion. Critical in generating exogenous oligosaccharides as SLe(x/a) mimetics is the stereoselective joining of specific mono- and di- saccharides that express functional groups integral in E-selectin-SLe(x/a) binding. Employing sulfur linkages to couple saccharide units enhances the biological stability of these complex carbohydrates. The synthesis of novel S-thiodisaccharides and C-disaccharides as SLe(x/a) precursors using the chiral sugars levoglucosenone, isomeric isolevoglucosenone and their functionalized analogs is described. The highly stereoselective functionalization of both enones at the C-4, C-3 and C-2 positions by the set of Michael addition reactions of reactive 1-thiosugars is reviewed. These functionalized S-thio di- and S-oligosaccharide precursors have direct application for use as templates in the synthesis of novel SLe(x/a)mimetics.     

Alkaline hydrolysis of oxaliplatin--isolation and identification of the oxalato monodentate intermediate

The alkaline degradation of the chemotherapeutic agent oxaliplatin has been studied using liquid chromatography. The oxalato ligand is lost in two consecutive steps. First, the oxalato ring is opened, forming an oxalato monodentate intermediate, as identified by electrospray ionization mass spectrometry. Subsequently, the oxalato ligand is lost and the dihydrated oxaliplatin complex is formed. The observed rate constants for the first step (k(1)) and the second step (k(2)) follow the equation k(1) or k(2) = k(0) + k(OH(-) )[OH(-)], where k(0) is the rate constant for the degradation catalyzed by water and k(OH(-) ) represents the second-order rate constant for the degradation catalyzed by the hydroxide ion. At 37 degrees C the rate constants for the first step are k(OH(-) ) = 5.5 x 10(-2) min(-1) M(-1) [95% confidence interval (CI), 2.7 x 10(-2) to 8.4 x 10(-2) min(-1) M(-1)] and k(0) = 4.3 x 10(-2) min(-1) (95% CI, 4.0 x 10(-2) to 4.7 x 10(-2) min(-1)). For the second step the rate constants are k(OH(-) ) = 1.1 x 10(-3) min(-1) M(-1) (95% CI, -1.1 x 10(-3) to 3.3 x 10(-3)) min(-1) M(-1) and k(0) = 7.5 x 10(-3) min(-1) (95% CI, 7.2 x 10(-3) to 7.8 x 10(-3) min(-1)). Thus, the ring-opening step is nearly six times faster than the step involving the loss of the oxalato ligand.     

Antimalarial efficacy of arteether against multiple drug resistant strain of Plasmodium yoelii nigeriensis

New quick-acting blood schizontocides are needed to contain the spread of multiple drug resistant strains of P. falciparum and for the treatment of the cerebral malaria cases. A multiple drug resistant strain of P. yoelii nigeriensis resistant to mefloquine (128 mg/kg x 6 days), quinine (300 mg/kg x 7 days) and chloroquine (64 mg/kg x 8 days) was found to be completely susceptible to arteether (a 30:70 mixture of alpha and beta enantiomers) and a dose of 5 mg/kg x 3 days by i.m. route was curative in Swiss mice. Artemisinin at 50 mg/kg x 7 days had only suppressive action against this strain.     

Estimation of a possible tumorigenic risk of styrene from daily intake via food and ambient air.

Concerns of a tumorigenic risk of styrene (ST) originate from the findings that styrene (ST) is metabolized to the genotoxic intermediate styrene-7,8-oxide (SO). Therefore, it was hypothesized that results of animal long-term studies with ST and SO together with the SO tissue burden are sufficient for conducting a 'worst case' estimate of the tumorigenic risk of ST. On this basis we predicted the excess human lifetime risk for lung tumors (p(EXL)) and the highest possible risk for other systemic tumors (p(HPS)) resulting from daily intake of ST via food and ambient air. As measures for p(EXL) the mean lifetime concentration of SO in the transitional zone of the lung and for p(HPS) the mean lifetime concentration of SO in blood were calculated using a physiological toxicokinetic model. For a daily oral intake of 12 microST, p(EXL) was obtained to be between 5x10(-9) and 2x10(-8) and p(HPS) to be between 7x10(-9) and 2x10(-8). Lifetime risks calculated for continuous exposure to 3 microg/m(3) ST in ambient air were between 8x10(-7) and 3x10(-6) (p(EXL)) and between 2x10(-8) and 4x10(-8) (p(HPS)). Although these values indicate very low risks, the actual risks are expected to be even by far smaller. This is discussed in detail for lung tumorigenesis.     

Serum nitric oxide metabolite (NO(x)) levels in hypertensive patients at rest: a comparison of age, gender, blood pressure and complications using normotensive controls

1. Hypertensive patients have pathophysiological changes such as atherosclerosis, endothelial dysfunction and inflammations. The patients' serum nitric oxide metabolite (nitrate/nitrite; NO(x)) levels were measured in peripheral blood using normotensive controls for comparison. 2. The NO(x) levels in 175 hypertensive patients with or without comorbid diseases (aged 37-95 years; average 50.6 +/- 0.8 years) were compared with those in 80 normotensive controls (aged 25-73 years; average 37.1 +/- 1.8 years). 3. The NO(x) levels increased with age in both the normotensive and hypertensive women, but not in men. No difference was noted in the NO(x) levels between the normotensive and hypertensive patients without comorbid diseases. The mean value of NO(x) in male hypertensive patients aged under 50 years was close to that of female patients aged 51-60 years. Hypertensive males aged 61-70 years showed almost the same NO(x) levels as those of female patients aged over 81 years. A male group of hypertensive patients with diabetes, hyperlipaemia and renal disorder had a significantly higher NO(x) level compared with a normotensive control group. However, in female groups, only hypertensive patients with hyperlipaemia showed higher serum NO(x) values compared with the normotensive group. 4. These findings suggest that: (i) the occurrence of NO(x) in the serum is not solely the outcome of high blood pressure; (ii) higher serum NO(x) levels in older women are because of an oestrogen deficiency-induced cardiovascular disease; (iii) ageing effects on the circulation system are more apparent in men than in women; and (iv) measurement of NO(x) levels in the serum is helpful for understanding the pathological progress in male hypertensive patients with diseases such as diabetes mellitus, hyperlipaemia and renal disorder.     

Stimulation of guinea pig isolated atria by aflatoxins.

Acute effects of aflatoxins (AF), and in particular cardiac actions, have not been examined as much as chronic toxicity. Thus, in the present study we evaluated the effects of specific AF on isolated guinea pig atria. Isoprenaline (ISO, 4x10(-9)), AFB(1) (3x10(-6) and 6x10(-5) M) and AFG(1) (3x10(-6) and 6x10(-6) M) contracted the isolated guinea pig atria, leaving the preparation hyperresponsive to ISO. These properties of AF are of interest as they could be responsible of certain cardiotoxic effects described in the literature.     

Interaction of selective compounds with muscarinic receptors at dispersed intestinal smooth muscle cells.

1. The characterization of muscarinic receptors on single cells of the guinea-pig ileum longitudinal smooth muscle, devoid of neuronal elements, was functionally studied by estimating the affinities of muscarinic antagonists on acetylcholine-induced contractions. 2. Atropine (5 x 10(-11) to 5 x 10(-6) M), 4-diphenylacetoxy-N-methyl-piperidine methiodide (4-DAMP, 5 x 10(-8) to 5 x 10(-6) M), cyclohexyl(4-fluoro-phenyl) (3-piperidinopropyl) silanol (pFHHSiD, 5 x 10(-7) to 5 x 10(-5) M) as well as pirenzepine (5 x 10(-7) to 5 x 10(-5) M) competitively antagonized the acetylcholine-dependent contractions with different affinities (atropine > 4-DAMP > pFHHSiD > pirenzepine). 3. Methoctramine (5 x 10(-7) to 5 x 10(-5) M), and AF-DX 116 (5 x 10(-6) and 5 x 10(-5) M) also showed antagonist properties but these deviated from simple competition. These compounds, which discriminate between M2 and M3 receptors, showed a potency lower than that of pirenzepine, the rank order of potencies being pirenzepine > methoctramine > AF-DX 116. When concentrations of AF-DX 116, methoctramine and pirenzepine were increased an unspecific contractile effect occurred. 4. McN-A-343, a partial agonist on intact guinea-pig longitudinal smooth muscle strips, on this preparation induced a weak contraction (about 7% in comparison to control) that was not reversed by antimuscarinic agents. 5. These data indicate that M3 rather than M2 receptor sites are present on this tissue.     

Use of derivatization reactions with adsorptive stripping voltammetry for determining fotemustine in biological samples.

A method is described for determining the new fotemustine antineoplastic in human serum. The method is based on the derivatization of the original molecule by means of diazotization and coupling reactions. The derivatization product is determined by means of adsorptive stripping voltammetry. The calibration graphs were linear over the range 6 x 10(-9)-8 x 10(-7) and 6 x 10(-10)-8 x 10(-8) M, according to whether the coupling reagent was 1-naphthylamine or 1-naphthol, respectively. At the same time, the detection limits are 4.1 x 10(-9) and 1.4 x 10(-10) M, respectively. The method was applied to determine this antineoplastic in human serum, after a liquid-liquid extraction process, from which recovery factors of 95.6% has been obtained.