OBJECTIVE:To report 2 cases of severe hypertriglyceridemia associated with the use of oral capecitabine.CASE SUMMARIES:The first patient was a 73-year-old woman with metastatic breast carcinoma who received capecitabine 2500 mg/m2/day in 2 divided doses for 2 weeks followed by a one week rest period. The baseline triglyceride level was 324 mg/dL; after 2 cycles of capecitabine, levels increased to 916 mg/dL. Although lipid-lowering treatment was initiated, triglyceride levels peaked at 1782 mg/dL by the end of the seventh cycle. Eight weeks after capecitabine treatment was stopped, triglyceride levels decreased to 118 mg/dL. The second patient was a 59-year-old man with metastatic colorectal carcinoma who was placed on capecitabine treatment at a dosage of 2500 mg/m2/day in 2 divided doses for 2 weeks followed by a one week rest period. The baseline triglyceride level was 244 mg/dL; levels peaked at 1455 mg/dL at the end of the fifth cycle. Capecitabine treatment was discontinued due to disease progression, and triglyceride levels decreased to 154 mg/dL after 11 weeks.DISCUSSION:The most frequently reported adverse effects of capecitabine are gastrointestinal and hematologic effects and palmar-plantar erythrodysesthesia. Drug-induced hyperlipidemia may appear more readily in individuals with hereditary lipoprotein lipase deficiency because decreased lipoprotein lipase activity might make these individuals more susceptible to a rise in triglyceride levels. The Naranjo probability scale indicated a probable relationship between capecitabine and severe hypertriglyceridemia.CONCLUSIONS:Capecitabine should be prescribed with care, especially in patients with preexisting hypertriglyceridemia. The question of whether capecitabine actually causes hypertriglyceridemia needs careful consideration, and the possible mechanism by which it may cause this adverse effect requires further investigation.

Drug interactions have been reported between 5-fluorouracil and cytochrome P450 2C9 (CYP2C9) substrates, S-warfarin and phenytoin. This study was performed to determine the influence of 5-fluorouracil on cytochrome P450 2C9 (CYP2C9) activity in colorectal cancer patients (n=17) receiving 5-fluorouracil. Losartan was used as a marker to assess CYP2C9 activity. Losartan and its CYP2C9 dependent metabolite, E-3174, were determined in urine. The ratios of urinary losartan/E-3174 before and after the 5-fluorouracil treatment were compared for each patient. Genotyping was performed to detect the CYP2C9*2 and CYP2C9*3. At the end of the first cycle of 5-fluorouracil, losartan/E-3174 ratio was increased by 28.0% compared to the pre-treatment values (P=0.15). In five patients recruited for phenotyping after three 5-fluorouracil cycles, the metabolic ratio was increased significantly by 5.3 times (P=0.03). The results suggest that in most patients 5-fluorouracil inhibited CYP2C9 activity. This inhibition was more pronounced when the total administered dose increased. This finding may help explain the mechanism of interaction between 5-fluorouracil and CYP2C9 substrates.

Bilirubin uridine diphosphate-glucuronosyltransferase (B-UGT) is the rate-limiting enzyme for the conjugation of bilirubin with glucuronic acid in its excretion process into the bile. Variations in B-UGT gene (UGT-1A1) have been related to disorders characterised by hyperbilirubinaemia. The aim of this study was to investigate whether the number of thymine-adenine repeats in the promoter region of UGT-1A1 was related to non-physiologic hyperbilirubinemia of unexplained aetiology in Turkish newborns. These patients (n=106) were genotyped for their thymine-adenine repeat number in the promoter region of UGT-1A1, and were divided into two groups according to their bilirubin level. Forty-nine newborns with bilirubin levels higher than 17 mg/dl within the first ten days of life comprised the hyperbilirubinaemia group and 25 newborns with bilirubin levels higher than 10 mg/dl after fifteen days of life formed the prolonged jaundice group. Thirty-two newborns were included as healthy controls. The observed frequencies for the wild-type six repeat allele thymine-adenine (TA(6)) within each subject group were similar (P>0.05; 75.5%, 78.0% and 73.4%, respectively). Likewise, the distribution of TA(6/6), TA(6/7) and TA(7/7) genotypes among three groups were similar. These results imply that the TA(7) repeat allele of UGT1A1 (UGT1A1*28) is a common variant in the Turkish population. Our results do not suggest an association between thymine-adenine repeat polymorphism of UGT1A1 and hyperbilirubinaemia of unexplained aetiology or prolonged jaundice in Turkish neonates.

BACKGROUND:Resistance to antiemetic treatment with 5-hydroxytryptamine type 3 (5-HT(3)) receptor antagonists is still a major problem resulting in patient discomfort and poor compliance to chemotherapy. We hypothesized that clinical resistance to 5-HT(3) antagonists is associated with the single-nucleotide polymorphism (3435C>T) in the gene that codes for the drug efflux transporter adenosine triphosphate-binding cassette subfamily B member 1 (ABCB1).METHODS:Patients with cancer (N = 216) treated with chemotherapeutic regimens composed of highly or moderately emetogenic agents were examined for their antiemetic responses to tropisetron, ondansetron, or granisetron. The efficacy of antiemetic treatment was documented by self-report charts for 5 days after chemotherapy. ABCB1 3435C>T genotype was determined to analyze its association with the antiemetic efficacy of 5-HT(3) antagonists.RESULTS:Within the first 24 hours of chemotherapy, the complete control rate of nausea and vomiting was higher in subjects with the ABCB1 TT genotype (n = 49) as compared with those with the CC (n = 60) or CT (n = 107) genotype (P = .044). The type of 5-HT(3) antagonists influenced the effect of genotype on antiemetic responses. The complete control rates were 92.9% in TT subjects (n = 14) in comparison to homozygote (47.6%, n = 21, P = .009) or heterozygote (56.1%, n = 41, P = .02) carriers of the 3435 C allele in granisetron-treated patients. However, during the delayed phase of chemotherapy, the complete control rates did not differ across genotypes.CONCLUSION:These results suggest that ABCB1 3435C>T polymorphism is associated with antiemetic treatment efficacy in patients with cancer treated with 5-HT(3) antagonists, particularly in granisetron-treated patients, during the short-term phase of chemotherapy.

2095 Background: Cyclophosphamide (CPA) is widely used for cancer chemotherapy and immunosuppression. It has been reported that CPA (but not adriamycin) could alter the activities of a variety of drug metabolizing enzymes in rats via multiple mechanisms. However, the effects of CPA in drug metabolism in human are largely unknown. Losartan metabolism has been suggested as a marker for determination of CYP2C9 activity, and caffeine is a commonly used probe to assess the metabolic activities of CYP1A2, CYP2A6, N-acetyltransferase 2 (NAT2) and xanthine oxidase (XO). The present study was designed to analyze the effects of CPA on these drug-metabolizing enzymes by using losartan and caffeine as probe drugs. Methods: A single oral dose of 25 mg losartan and a cup of coffee (approximately 100 mg caffeine) was given to 10 operable breast cancer patients three times (two days before, after 2–4 hours and after three weeks of first cycle of adjuvant CPA/adriamycin chemotherapy [CPA 600 mg/m2/day, adriamycin 60 mg/m2/day, repeated in every 3 weeks]). Losartan, caffeine and their metabolites were analyzed by using high pressure liquid chromatography. Results: CYP1A2 and NAT2 activities were increased after the administration of cyclophophamide/adriamycin chemotherapy by 37% and 50%, respectively (p=0.02). CYP2A6 activity was reduced by 14% on the day of cyclophophamide/adriamycin administration (p=0.03). There was no acute or chronic effect of the chemotherapy administration on CYP2C9 and XO activities. Conclusion: Differential effect of CPA/adriamycin treatment on drug metabolizing enzyme activities might add an important information on efficacy and toxicity, as well as drug related interactions. This study was supported by Turkish Scientific and Technical Research Council (SBAG-COSTB15–2356). No significant financial relationships to disclose.

Background and Aim: Previous data indicate that the urinary losartan/E-3174 ratio is a marker for cytochrome P450 (CYP) 2C9 activity in vivo. The functional impact of CYP2C9(star)5, (star)6, (star)8, and (star)11 polymorphisms in vivo has not been investigated previously in humans.Methods: A single oral dose of losartan (25 mg) was given to 19 Beninese subjects with CYP2C9(star)1/(star)1 (n = 9), (star)1/(star)5 (n = 1), (star)1/(star)6 (n = 1), (star)1/(star)8 (n = 2), (star)1/(star)11 (n = 3), (star)5/(star)6 (n = 1), (star)5/(star)8 (n = 1), and (star)8/(star)11 (n = 1) genotypes. Concentrations of losartan and its active metabolite E-3174 were determined in urine from 0 to 8 hours by HPLC. The losartan/E-3174 metabolic ratio was used as a measure of losartan oxidation in vivo.Results: The urinary losartan/E-3174 ratio in the various genotypes was as follows: 1.85 +/- 2.4 (mean +/- SD) for CYP2C9(star)1/(star)1, 14.6 for CYP2C9(star)1/star5, 4.2 for CYP2C9(star)1/(star)6, 188 for CYP2C9(star)5/(star)6, 11.6 for CYP2C9(star)5/(star)8, 0.44 +/- 0.13 (mean +/- SD) for CYP2C9(star)1/(star)8, 2.2 for CYP2C9(star)8/(star)11, and 5.72 +/- 4.5 (mean +/- SD) for CYP2C9(star)1/(star)11. Compared with the CYP2C9(star)1/(star)1 genotypes, the losartan/E-3174 ratio was significantly different in the CYP2C9(star)5 allele carriers (CYP2C9(star)1/(star)5, CYP2C9(star)5/(star)8, and CYP2C9(star)5/(star)6 genotypes) (P = .01, Mann-Whitney) but was not different in CYP2C9(star)1/(star)8 (P = .16) and CYP2C9(star)1/(star)11 (P = .11) carriers. The urinary losartan/E-3174 ratio of the single CYP2C9(star)1/(star)6 subject was higher than the 95% confidence interval of the mean of the CYP2C9(star)1/(star)1 group (0.0-3.7), whereas the metabolic ratio of the CYP2C9(star)8/(star)11 carrier was inside the 95% confidence interval of the means of the CYP2C9(star)1/(star)1 and CYP2C9(star)1/(star)11 groups (0.0-18).Conclusions: The CYP2C9(star)5 and (star)6 alleles are associated with decreased enzyme activity in vivo compared with the wild-type variant, whereas the CYP2C9(star)8 and (star)11 variants did not appear to have large in vivo effects.

TO THE EDITOR: CYP2C9 is the major isoenzyme responsible for the inactivation of S-warfarin. The CYP2C9 enzyme is a polymorphic gene with the most common allele *1 and rare variants *2 and *3 in white persons.1 Warfarin maintenance doses and bleeding complications are associated with these CYP2C9 mutations.2 Here we describe a patient who required high doses of warfarin up to 15 mg/day with, contrary to expectations, low CYP2C9 activity and CYP2C9*1*2 genotype. Case Report. A 44-year-old Turkish woman was admitted to the hospital due to transient loss of vision. Medical history was remarkable for headache, hypertension, and epilepsy. She was diagnosed with antiphospholipid antibody syndrome. Her baseline international normalized ratio (INR) was 1.08. Warfarin was started in July 2002 at a dose of 5 mg/day and was gradually increased to 15 mg/day until INR values reached the desired level of 2.5–3 within 10 months (Table 1). Initial concomitant therapy included verapamil 120 mg/day and barbexaclone 100 mg/day. Barbexaclone was gradually withdrawn in August 2002 and replaced with gabapentin 900 mg/day. She was not on a special diet and did not receive vitamin supplements regularly. We determined the CYP2C9 enzyme activity using a single oral 25-mg dose of losartan as a probe drug3 in August 2003. The ratio of losartan to E-3174 in the patient’s urine was 3.2, which is threefold higher than the population mean for the CYP2C9*1*1 genotype.3 This value suggests quite low activity of CYP2C9 in this patient. The patient’s genotype was determined as CYP2C9*1*2 by using a polymerase-chain reaction–based endonuclease digestion method.1 Written informed consent was obtained from the subject for the phenotyping and genotyping procedure. Discussion. Our patient’s anticoagulant treatment with warfarin was compounded by the persistence of a low INR. As warfarin is a substrate for CYP2C9, low enzyme activity would result in slow inactivation of warfarin. However, contrary to expectations, the present case had low activity of CYP2C9, but still required high doses of warfarin. It has been reported that other factors, such as drug interactions, vitamin K dietary intake, and abnormalities in vitamin K epoxide reductase can also affect anticoagulation with warfarin.2,4 The patient’s daily vitamin K intake seemed to be appropriate. However, this does not rule out any abnormalities in vitamin K epoxide reductase in the patient. Another possible reason for warfarin resistance in this patient could be the concomitant use of barbexaclone, a phenobarbital-like drug that is known to induce CYP2C9. However, warfarin doses had to be increased even after the withdrawal of barbexaclone. In this patient, analysis of concentrations of S-warfarin and 7-hydroxywarfarin, a major metabolite of S-warfarin primarily produced by CYP2C9, would give more valuable information; however, we used losartan as a probe to measure real-time CYP2C9 activity. Although CYP2C9 is important for the metabolism of warfarin,2 our case supports the view that CYP2C9 genotyping and phenotyping may not have a predictive value in every subject.4,5

The inhibitory effect of the selective M3 musarinic acetylcholine receptor antagonist, 4-diphenylacetoxy-N-methylpiperidine methobromide (4-DAMP, 0.1–10 μM) on nicotine (100 μM)-induced nitrergic relaxation was investigated in comparison to d-tubocurarine (0.1–10 μM) and hexamethonium (0.1–10 μM) by using phenylephrine (1 μM)-precontracted rat anococcygeus muscles in vitro. Nicotine produced a 60.1± 2.4% (n = 40) inhibition of phenylephrine precontractions. But this relaxant response was at a significantly lower magnitude of 20.2± 4.6% (n = 18, P < 0.01 vs. control) in the presence of the nitric oxide synthase (NOS) blocker NG-nitro-L-arginine methyl ester (L-NAME, 30 μM), and it was 26.5± 5.5% (n = 8, P < 0.01 vs. control) in the presence of the soluble guanylate cyclase inhibitor methylene blue (30 μM). However, aminoguanidine (100 μM), a relatively selective blocker of the inducible nitric oxide synthase (iNOS), had no significant effect. Similarly, other iNOS inhibitors such as dexamethasone (5 mg/kg) or L-canavanine (100 mg/kg) did not modify contractile nor relaxant responses when they were given in vivo, concomitantly with Escherichia coli endotoxin (1 mg/kg, ip) 4 h before the isolation of the tissues. 4-DAMP, hexamethonium, and d-tubocurarine inhibited nicotine-induced relaxation in a concentration-dependent manner with the following order of potency: 4-DAMP > hexamethonium > d-tubocurarine with IC50 values being 0.47± 0.04 μM, 0.75± 0.06 μM, and 1.02± 0.05 μM, respectively. Therefore, it was concluded that the selective M3 muscarinic acetylcholine receptor antagonist 4-DAMP also possesses potent antagonistic action on nicotinic receptors of peripheral nitrergic neurons that innervate the rat anococcygeus muscle. Drug Dev. Res. 46:148–154, 1999. © 1999 Wiley-Liss, Inc.

The antagonistic potencies of some methoxy-2-aminotetralin derivatives on nicotinic type acetylcholine receptors were compared in rat anococcygeus muscle and frog rectus abdominis muscle preparations. Stimulation of intrinsic non-adrenergic non-cholinergic (NANC) nerves with nicotine (100 mumol/l) produced a 65.7 +/- 3.2% relaxation in phenylephrine (1 mumol/l) precontracted (2.53 +/- 0.20 g) preparations (n = 17). 2-Aminotetralin derivatives inhibited the nicotine-induced relaxations in rat anococcygeus muscle in a concentration-dependent manner with the following order of potency: BDI-60 > BDI-85 > BDI-51. Preincubation of frog rectus abdominis muscles with the test compounds caused noncompetitive antagonism as reflected by significant reductions in the maximum contractions obtained with nicotine. The order of potency according to their pD2' values was BDI-60 > BDI-85 > BDI-51. All three compounds possess antagonistic action with the same order of potency on both neuronal and muscular type nicotinic acetylcholine receptors. It has been concluded that doubling the n-propyl residue on the 2-amino moiety causes an increase in the antagonistic potency on nicotonic type acetylcholine receptors, while shifting of the 8-methoxy residue to the fifth position reduces it.

The difference between the responses of phenylephrine (1 microM)-precontracted vascular (endothelium-denuded rat or rabbit aortic strips) and nonvascular (rat anococcygeus muscle) smooth muscles to acetylcholine (0.1-100 microM) was investigated when they were mounted co-axially inside the tracheas isolated from normal or ovalbumin-sensitized guinea-pigs. Acetylcholine produced concentration-dependent relaxations in both types of bioassay tissues. These relaxations, previously shown to be due to the release of airway epithelium-derived relaxing factor(s), were significantly attenuated when the epithelial layer of the tracheas was removed mechanically (as confirmed by histological examination). There were no significant differences in responsiveness to acetylcholine between vascular strips mounted inside the epithelium-intact normal or sensitized tracheas. The phenylephrine-induced precontraction was significantly more pronounced in rat anococcygeus muscles mounted inside sensitized tracheas as compared to tissues mounted inside control tracheas. The acetylcholine-induced relaxations were significantly decreased but this effect disappeared when the concentration of phenylephrine was reduced to obtain a similar precontraction level as in tissues mounted inside control tracheas. The responsiveness of both vascular strips and anococcygeus muscles to acetylcholine was attenuated when they were mounted inside sensitized tracheas and incubated with ovalbumin for 20 min, which may be explained by the epithelial damage induced by ovalbumin challenge. This attenuation was absent when co-axial pairs, utilizing normal tracheas, were used. These results indicate a difference in response patterns of the rat anococcygeus muscle and vascular strips in ovalbumin-sensitized tracheas, which should be taken into consideration in co-axial bioassay studies.