Characterization of nelfinavir binding to plasma proteins and the lack of drug displacement interactions.

OBJECTIVES: To determine the characteristics of the binding of nelfinavir and active M8 to alpha1-acid glycoprotein (AAG) and human serum albumin (HSA), and to examine the displacement effects of drugs binding extensively to AAG (ritonavir and saquinavir) or to HSA (salicylic acid and valproic acid). METHODS: Free drugs were separated by equilibrium dialysis after incubation with human plasma or purified plasma proteins and after co-incubation with potential displacers. Association constants were estimated from double-reciprocal plots of the data. RESULTS: Nelfinavir and M8 free fractions [fractions of unbound drug (fus)] were 0.42+/-0.08% (mean+/-standard deviation) and 0.64+/-0.07%, respectively. For the two analytes, respectively, association constants were 7.25 x 10(7)/m and 3.33 x 10(7)/m for AAG and 1.11 x 10(6)/m and 7.92 x 10(5)/m for HSA. Nelfinavir fu in an AAG solution was significantly (P < 0.01) increased by the addition of ritonavir or saquinavir, whereas it was unaltered by addition of these drugs to whole plasma. Similarly, fu in an HSA solution was significantly increased (P < 0.01) by the addition of salicylic acid or valproic acid, whereas there was no difference in the free fraction in plasma. CONCLUSIONS: The affinity of nelfinavir for human plasma proteins was higher than that of M8, and both nelfinavir and M8 showed higher affinity to AAG than to HSA. The free fraction of nelfinavir was not affected by drugs that bind extensively to AAG or albumin when these drugs were added to whole plasma in combination, suggesting a compensatory effect of alternate binding proteins.

St. John's Wort (Hypericum perforatum) induces overexpression of multidrug resistance protein 2 (MRP2) in rats: a 30-day ingestion study.

St. John's Wort (Hypericum perforatum, SJW) has been used as a herbal medicine for the treatment of depression in oral doses of 900-1050 mg/day in humans. However, the ingestion of SJW was reported to cause interactions with drugs. In the present study, we examined the effects of SJW treatment on the induction of drug transporters and enzymes in rats. An immunoblot analysis was performed to quantify the expression of the transporters and enzymes. SJW was given at a dose of 400 mg/kg/day, since it was reported that 400 mg/kg/day is antidepressant effective dose in rats. When SJW was administered for 10 days, the amounts of multidrug resistance protein 2 (MRP2), glutathione S-transferase-P (GST-P) and cytochrome P450 1A2 (CYP1A2) in the liver were increased to 304%, 252% and 357% of controls, respectively, although the amounts of P-glycoprotein and multidrug resistance protein 1 were not changed. Under the same conditions, an increase of MRP2 in the kidney was not observed. The increase in the levels of each protein was maximal at 10 days after SJW treatment and lasted for at least 30 consecutive days. These results suggest that SJW induces hepatic MRP2, GST-P and CYP1A2 overexpressions, and thus, it could affect drug metabolism, conjugation and disposition.

Effects of ascorbic acid on interactions between ciprofloxacin and ferrous sulphate, sodium ferrous citrate or ferric pyrophosphate, in mice.

The absorption of ciprofloxacin has been reported to be impaired by concomitant administration of ferrous sulphate. The effects of sodium ferrous citrate and ferric pyrophosphate, which have been used as extensively as ferrous sulphate, on the absorption of ciprofloxacin were compared with that of ferrous sulphate. The effects of ascorbic acid on the interactions between ciprofloxacin and each iron compound were studied in mice. Mice were treated orally with ciprofloxacin (50 mg kg(-1)) alone, the iron compound (ferrous sulphate, sodium ferrous citrate or ferric pyrophosphate; 50 mg elemental iron kg(-1)) alone, ciprofloxacin with each iron compound or ciprofloxacin in combination with each iron compound and ascorbic acid (250 mg kg(-1)). The maximum serum concentration of ciprofloxacin was significantly (P < 0.01) reduced from 1.15+/-0.11 microg mL(-1) (ciprofloxacin alone) to 0.17+/-0.01, 0.27+/-0.01 or 0.28+/-0.02 microg mL(-1), respectively, when ferrous sulphate, sodium ferrous citrate or ferric pyrophosphate was administered along with ciprofloxacin. The addition of ascorbic acid did not affect the inhibitory effects of each iron compound on the absorption of ciprofloxacin. Ciprofloxacin did not affect the variation of serum iron levels after administration of each iron compound. The addition of ascorbic acid significantly (P < 0.01) enhanced the increase in serum iron concentration after administration of sodium ferrous citrate, showing an increase from 270+/-6 microg dL(-1) to 463+/-11 microg dL(-1) compared with an increase from 248+/-8 microg dL(-1) to 394+/-18 microg dL(-1) after administration of sodium ferrous citrate alone. Ascorbic acid also caused a significant (P < 0.01) increase in serum iron concentration from 261+/-16 microg dL(-1) to 360+/-12 microg dL(-1) after administration of ferric pyrophosphate, although it did not affect the levels after ferrous sulphate administration. The results suggest that sodium ferrous citrate and ferric pyrophosphate should not be administered with ciprofloxacin (as for ferrous sulphate) and that sodium ferrous citrate is converted to the ferric form more easily than ferrous sulphate. This difference in convertibility might contribute to a clinical difference between sodium ferrous citrate and ferrous sulphate.

Changes in adrenocorticotropic hormone (ACTH) release from the cultured anterior pituitary cells of streptozotocin-induced diabetic rats.

We examined ACTH release from cultured anterior pituitary cells of streptozotocin (STZ)-induced diabetic rats. Rats 1 week after the injection of STZ (55 mg/kg, i.v.) were used as a short-term diabetic model, while rats 8 weeks after the injection of STZ were used as a long-term diabetic model. ACTH release induced by corticotropin-releasing factors (CRF) was significantly increased in the short-term diabetic rats, whereas ACTH release decreased in the long-term diabetic rats. A stimulator of adenylate cyclase, forskolin, caused marked increases in ACTH release in short-term diabetic rats, whereas it did not affect the long-term diabetic rats. An L-type Ca2+ channel agonist, BAY K 8644, did not affect ACTH release in the short-term diabetic rats, although it decreased ACTH release in long-term diabetic rats. In addition, CRF-induced ACTH release also increased in normal anterior pituitary cells cultured under high glucose conditions (25 mmol/L) for 5 d. These results suggest that the increase in the CRF-induced ACTH release from cultured anterior pituitary cells of short-term diabetic rats appears to involve the cAMP system in part. In contrast, the decrease in the CRF-induced ACTH release from the cultured anterior pituitary cells of long-term diabetic rats may indicate a change in the properties of the L-type Ca2+ channel coupled with the CRF receptor, or in the CRF receptor itself.

The angiotensin AT1 receptor antagonist, losartan, induces barrel rotation in the rat.

Intracerebroventricular injections of [Arg8]vasopressin (500 ng/rat) or endothelin-1 (70 ng/rat) into the right lateral ventricle induced rotation along the long axis of the body (barrel rotation) in rats. Losartan (10-200 microg/rat), an angiotensin AT1 receptor antagonist, also evoked barrel rotation, which was not inhibited by vasopressin and endothelin receptor antagonists. However, barrel rotation was not observed after injections of high doses of another angiotensin II receptor antagonist, [Sar1,Ile8]angiotensin II (100 microg/rat), or after angiotensin II (10 microg/rat). The results indicate that losartan does evoke barrel rotation which may be not mediated via vasopressin and endothelin receptors.

[Prevention of stomatitis induced by anti-cancer drugs].

A randomized control trial study was carried out to evaluate the effect of allopurinol mouth wash on stomatitis induced by chemotherapy in gynecologic patients. Chemotherapeutics used consisted of 5-FU+CDDP (PF) given to 10 patients and vincristine and actinomycin-D+cyclophosphamide (VAC) given to 5. Allopurinol mouth wash was prepared for patients to rinse their mouth with the solution 4-5 times daily before and after treatment with anti-cancer drugs. The Japan Society For Cancer Therapy's criteria for stomatitis were used. In the control group, stomatitis occurred in 9 of the 10 patients receiving PF therapy and in all of the 5 receiving VAC. In contrast, stomatitis was observed in only 2 of the 10 patients receiving PF therapy and 2 of the 5 VAC in the allopurinol-treated group. Allopurinol mouth wash showed a marked effect on stomatitis induced by chemotherapy.

Preventive effect of taurine against acute paraquat intoxication in beagles.

The continuous infusion of taurine markedly protected against paraquat (PQ)-induced oliguria in beagles. Pharmacokinetic studies revealed that taurine infusion increased the blood concentration of PQ and reduced the net content in the kidney and, to a lesser extent, in the lung. The excretion of PQ into the urine was unaltered. The infusion of glycine did not have such effects.

Evolution of infectious mononucleosis into Epstein-Barr virus carrying monoclonal malignant lymphoma.

A monoclonal malignant lymphoma was diagnosed in a 30-month-old Japanese boy, who, since the age of 12 months, had had chronic, recurrent infectious mononucleosis manifested by repeated episodes of severe cough and high fever accompanied by marked lymphadenopathy and hepatosplenomegaly and high serum Epstein-Barr virus (EBV) antibody titres. The diagnosis of Burkitt's lymphoma was made when a cervical lymph-node biopsy specimen revealed massive proliferation of immature B-cells with starry-sky histiocytes. These lymph-node cells were characterised by a translocation between chromosomes 10 and 17. There were approximately 9 EBV genome-equivalents per cell. Most cells were positive for nuclear antigen (EBNA); early antigen (EA) and viral capsid antigen (VCA) were also detected. The presence of EBV was supported by finding that the cell-free lymph-node extract transformed cord-blood lymphocytes into EBNA-positive blast cells. The proportion of EA-positive and VCA-positive cells increased rapidly in culture for 24 h, then the positive cells degenerated rapidly and completely. The cells also contained numerous herpes-type virus particles. The child improved considerably with cytostatic treatment and has been in remission for 2 years.

Metabolites of piperidine in rat urine.

Piperidine is one of pharmacologically active biogenic amines. While two pathways for piperidine production have been reported, little is known about metabolism of the compound. In the present study, piperidine and its hydroxylated, conjugated and unknown metabolites were detected in rat urine by radiochromatographic analysis. Using GC-MS technique, it was confirmed that 3-hydroxypiperidine and 4-hydroxypiperidine are major metabolites of piperidine of either exogenous or endogenous origin. The findings substantiate the existence of a mechanism which inactivates piperidine in the living body, since both metabolites lack the potent pharmacological activities as those induced by piperidine.