Hello.

Re:
"
Apxr - the Medscape links that you provided are inaccessible (don't you hate that?) A log-in is needed now. I've been able to read some of their abstracts/articles, but not today!
"

Blast it! Now I can't access the info either. Medscape is annoying; must remember that.





Anyway, here's the excerpt that I intended to share:

"
Introduction
Metronidazole is a substituted imidazole Antibiotic that is widely used to treat anaerobic bacterial, Helicobacter pylori, and protozoal infections. It is also commonly included in bowel-preparation regimens before colorectal surgery. Metronidazole is reported to have several clinically significant drug interactions due to the inhibition of oxidative drug metabolism. However, the effects of metronidazole on the activity of specific cytochrome P450 (CYP) isoforms has not been reported, and several of the reported drug interactions are based on single case reports.[1-4]

Although metronidazole appears to be an important inhibitor of CYP2C9 activity,[5-7] the evidence supporting inhibition of CYP3A activity in humans is weak.[1-4,7-10] Standard drug interaction textbooks and computer software programs routinely warn of an interaction between metronidazole and common CYP3A substrates, including cyclosporine and carbamazepine.[11,12] The clinical relevance of these interactions, especially with a short course of therapy administered preoperatively or in the treatment of Trichomonas vaginalis infections, is not clear.
"






and also this small one:

"
..Metronidazole does not affect the clearance of theophylline, a CYP1A2 substrate,[25,26] and contrary to several case reports,[1-4] controlled studies involving substrates for CYP3A4, such as midazolam,[10] alprazolam,[7] diazepam,[8] ethinyl estradiol,[9] and R-warfarin,[5] also indicate no important inhibition of metabolism due to metronidazole. The lack of effect seen in our study is consistent with the other controlled studies involving CYP3A4 substrates.

One potential explanation to resolve the apparent discrepancy between the controlled studies and case reports regarding the effect of metronidazole on metabolism of CYP3A substrates is that the case reports all included patients who were acutely ill.[1-4] The case reports may represent a drug-disease interaction, rather than a drug-drug interaction involving metronidazole...
"


..which seems to suggest an 'apparent discrepancy' both in the results and/or in the understanding of certain interactions with Metronidazole -yes, Benzodiazepines included- when tested in the field. And those are the experts talking.






And here's the whole article from:
http://www.medscape.com/viewarticle/409792_print


"
Effects of Metronidazole on Hepatic CYP3A4 Activity

Curtis E. Haas, Pharm.D., David C. Kaufman, M.D., and Robert C. DiCenzo, Pharm.D.

Pharmacotherapy 21(10):1192-1195, 2001. © 2001 Pharmacotherapy Publications
Abstract and Introduction
Abstract
Study Objective. To evaluate the effect of a short course of oral metronidazole, commonly used for bowel-preparation regimens, on hepatic cytochrome P450 (CYP) 3A4 activity, as measured by the [14C N-methyl]-erythromycin breath test (ERMBT) in healthy volunteers.

Design. Prospective, nonrandomized, interventional study.

Setting. University-affiliated, community, teaching hospital.

Subjects. Five healthy male volunteers.

Intervention. Subjects underwent a baseline ERMBT in the morning before receiving three oral doses of metronidazole 500 mg administered at 3 P.M., 7 P.M., and 11 P.M. Repeat ERMBTs were performed at 24, 72, and 96 hours after the initial ERMBT. Changes in ERMBT values were compared with baseline results using Freidman's repeated-measures analysis of variance on ranks.
Measurements and Main Results. The ERMBT values did not change significantly compared with baseline (p=0.82). Median (range) ERMBT values expressed as a percentage of baseline at 24, 72, and 96 hours were 110.3 (96.2-136.9), 101.3 (99.3-115.0), and 101.8 (95.5-116.3), respectively.
Conclusion. A short course of oral metronidazole does not result in a significant change in hepatic CYP3A4 activity as measured by the ERMBT.

Introduction
Metronidazole is a substituted imidazole Antibiotic that is widely used to treat anaerobic bacterial, Helicobacter pylori, and protozoal infections. It is also commonly included in bowel-preparation regimens before colorectal surgery. Metronidazole is reported to have several clinically significant drug interactions due to the inhibition of oxidative drug metabolism. However, the effects of metronidazole on the activity of specific cytochrome P450 (CYP) isoforms has not been reported, and several of the reported drug interactions are based on single case reports.[1-4]

Although metronidazole appears to be an important inhibitor of CYP2C9 activity,[5-7] the evidence supporting inhibition of CYP3A activity in humans is weak.[1-4,7-10] Standard drug interaction textbooks and computer software programs routinely warn of an interaction between metronidazole and common CYP3A substrates, including cyclosporine and carbamazepine.[11,12] The clinical relevance of these interactions, especially with a short course of therapy administered preoperatively or in the treatment of Trichomonas vaginalis infections, is not clear.

We recently completed a study evaluating the effects of major surgery on CYP3A4 activity. One of the patient cohorts underwent partial or complete colon resection and routinely received several doses of oral metronidazole the day before surgery. Since the effect of the oral metronidazole on preoperative hepatic CYP3A4 activity was unknown, we conducted a study with healthy volunteers to evaluate the effect of the preoperative metronidazole regimen on CYP3A4 activity, as measured by the [14C N-methyl]-erythromycin breath test (ERMBT).

Methods
Five healthy male volunteers aged 25-40 years participated in the study. These subjects had no known acute or chronic medical conditions and were not taking any prescription or over-the-counter drugs. All subjects were nonsmokers and refrained from alcohol consumption for at least 48 hours before and during the study. The study protocol was approved by the ViaHealth Clinical Investigations Committee and the Radiation Safety Committee. All subjects provided written informed consent.

On day 1 of the study, subjects underwent an ERMBT (Metabolic Solutions, Inc., Nashua, NH) between 8 A.M. and 9 A.M. The test was conducted according to the manufacturer's recommended procedures. In brief, a 3-µCi dose of [14C N-methyl]-erythromycin (< 0.05 mg) was injected over 1 minute into an antecubital or other prominent vein of the forearm. Twenty minutes after completion of the injection, a breath sample was collected, using the breath collection kit provided by the manufacturer. Later that day, metronidazole 500 mg (UDL, Rockford, IL) was taken orally at 3 P.M., 7 P.M., and 11 P.M.

Approximately 24, 72, and 96 hours after the first breath test, between 8 A.M. and 9 A.M., subjects had a repeat ERMBT, performed as described above. These times were chosen to be equivalent to the preoperative test and the 48-hour and 72-hour postoperative tests performed during the study of colorectal surgery patients. The ERMBTs were performed at approximately the same time each day to eliminate concern about variation in CYP3A4 activity throughout the day. To control for the possibility of a carryover effect from the previous dose, a breath sample was collected just before each of the three doses of [14C N-methyl]-erythromycin. Residual radioactivity from the previous 14C-erythromycin injection was measured and subtracted from the 20-minute postdose breath sample. A small amount of 14C-erythromycin remains in the body after 24 hours and is metabolized to CO2 (Wagner DA, personal communication, June 15, 2001).[13] After completion of the last ERMBT on day 5 of the study, the subjects' participation was ended.

Breath samples were shipped immediately to Metabolic Solutions, Inc., where 14CO2 content was measured by standardized procedures. Measurements were performed using a Tri-Carb 2100TR liquid scintillation counter (Packard Instrument Company, Inc., Meriden, CT). The accuracy and inter- and intra-run precision for high and low controls all had a percentage coefficient of variation below 0.5%. The percentage of the erythromycin dose demethylated in the first hour was calculated using a validated method.[14,15]

To account for interindividual variation in baseline CYP3A4 activity, the ERMBT results from days 2, 4, and 5 were converted to percentage of the baseline value for each subject. Changes in ERMBT results as percentage demethylated in the first hour and as a percentage of the baseline value were compared using a Friedman repeated-measures analysis of variance on ranks. The statistical tests were performed using SigmaStat version 2.03 (SPSS, Inc., San Rafael, CA).

Results
Median (range) ERMBT results expressed as a percentage of the dose demethylated in the first hour at baseline, 24, 72, and 96 hours were 1.84 (1.11-2.26), 1.96 (1.61-2.47), 1.79 (1.26-2.29), and 1.94 (1.13-2.26), respectively. Median (range)ERMBT values expressed as a percentage of baseline at 24, 72, and 96 hours were 110.3 (96.2-136.9), 101.3 (99.3-115.0), and 101.8 (95.5-116.3), respectively. Figure 1 shows the results for the five subjects. Regardless of how the data are presented, there was no significant change in the ERMBT results following the short course of oral metronidazole (p=0.82 for both analyses). The percentage change in baseline ERMBT was more variable at the 24-hour time point, due to two subjects having an apparent increase in hepatic CYP3A4 activity. These increases were comparable to intrasubject variability reported previously with the ERMBT.[16]

Figure 1. Erythromycin breath test (ERMBT) results for individual subjects (percentage of the erythromycin dose demethylated in the first hour).

Discussion
The activity of hepatic CYP3A4 isoenzyme was estimated by the ERMBT, which uses a trace dose of intravenous [14C-N-methyl]-erythromycin. The N-demethylation of erythromycin is catalyzed by CYP3A4, and the appearance rate of 14CO2 in the breath has been correlated with hepatic CYP3A4 content.[17,18] In addition, ERMBT results correlate with the clearance of known CYP3A4 substrates,[14,19,20] increase with the administration of known inducers,[16] and decrease after administration of known inhibitors.[16,21-24] We chose the ERMBT for our studies since it is minimally invasive, well tolerated, and can be easily performed on many occasions to detect serial changes in activity over a short time.

Data on the effects of metronidazole on specific pathways of drug metabolism are limited. Available evidence suggests that metronidazole may inhibit metabolism of the CYP2C9 substrates S-warfarin[5] and phenytoin,[7] although the results with phenytoin have not been consistent.[8] Metronidazole does not affect the clearance of theophylline, a CYP1A2 substrate,[25,26] and contrary to several case reports,[1-4] controlled studies involving substrates for CYP3A4, such as midazolam,[10] alprazolam,[7] diazepam,[8] ethinyl estradiol,[9] and R-warfarin,[5] also indicate no important inhibition of metabolism due to metronidazole. The lack of effect seen in our study is consistent with the other controlled studies involving CYP3A4 substrates.

One potential explanation to resolve the apparent discrepancy between the controlled studies and case reports regarding the effect of metronidazole on metabolism of CYP3A substrates is that the case reports all included patients who were acutely ill.[1-4] The case reports may represent a drug-disease interaction, rather than a drug-drug interaction involving metronidazole. It is increasingly well appreciated that acute illness and the associated acute inflammatory response can result in a downregulation of drug metabolism by CYP enzymes; this is often referred to as a drug-cytokine interaction.[27,28]

It is also possible that metronidazole inhibits intestinal CYP3A4 to a much greater extent than hepatic CYP3A4, possibly due to high concentrations of metronidazole in the lumen of the intestine. Intestinal CYP3A4 inhibition leading to increased oral bioavailability could explain the case reports of drug interactions involving cyclosporine,[1,4] tacrolimus,[4] and quinidine.[3] However, one study reported that metronidazole had no effect on the pharmaco-kinetics of midazolam or 1¢-hydroxymidazolam, or on the ratio of midazolam:1¢-hydroxymidazolam after oral administration of midazolam.[10] This report argues against an effect of metronidazole on intestinal CYP3A4 activity.

P-glycoprotein (P-gp) is a transmembrane glycoprotein that acts as a drug efflux pump across epithelial cell membranes of many organs, including the intestinal wall.[29,30] Cyclosporine, tacrolimus, and quinidine,[30] but not midazolam,[31] are P-gp substrates. If metronidazole inhibits P-gp activity within the intestinal epithelium, the absorption and oral bioavailability of P-gp substrates might be increased, while there would be no expected effect on the absorption of oral midazolam. It is unknown whether metronidazole affects P-gp activity.

In this study, a short course of oral metron-idazole, commonly used for bowel-preparation regimens, did not result in a significant change in CYP3A4 activity as measured by the ERMBT. Since the single 2-g oral dose commonly used to treat vaginitis secondary to Trichomonas vaginalis represents a similar dose and duration of exposure, we anticipate a lack of interaction with this regimen. These results do not exclude the possibility of a significant effect of metronidazole on CYP3A4 activity at a higher dose or a longer duration of treatment. This study involved healthy volunteers, and it is possible that a drug interaction may be more apparent in acutely ill patients.

Another limitation of this study is its small sample size, which may have led to a type II error. We measured 15 ERMBT results after baseline measurements in five subjects. The average baseline value was 1.75%/hour, with an average difference from baseline of 0.38%/hour on repeated measures. The standard deviation of the average change from baseline was 0.09%/hour. Clinically important inhibitors of hepatic CYP3A4, including ketoconazole,[22, 23] clarithromycin,[25] amprenavir,[23,24] and delavirdine,[21] have been reported to decrease baseline ERMBT results by 65-85%. We assume that a 40% decrease of ERMBT from baseline is the smallest clinically important change in CYP3A4 activity to detect. The probability that the true change in ERMBT was as high as 40% in our study is considerably less than 0.01. Based on these estimates, it is unlikely that our limited sample size resulted in a type II error that failed to detect a clinically important change in hepatic CYP3A4 activity.

Drug-interaction screening software programs routinely warn of drug interactions between metronidazole and CYP3A substrates. However, our results indicate that these warnings are not clinically relevant for the preoperative patient receiving metronidazole as part of a bowel-preparation regimen. Since metronidazole is a common drug, further investigation into its effects on the activity of specific CYP isoenzyme pathways, P-gp activity, and clinically important substrates is indicated.

References

1. Zylber-Katz E, Rubinger D, Berlatzky Y. Cyclosporine interactions with metronidazole and cimetidine [letter]. Drug Intell Clin Pharm 1988;22:504-5.
2. Patterson BD. Possible interaction between metronidazole and carbamazepine [letter]. Ann Pharmacother 1994;28:1303-4.
3. Cooke CE, Sklar GE, Nappi JE. Possible pharmacokinetic interaction with quinidine: ciprofloxacin or metronidazole? Ann Pharmacother 1996;30:364-6.
4. Herzig K, Johnson DW. Marked elevation of blood cyclosporin and tacrolimus levels due to concurrent metronidazole therapy. Nephrol Dial Transplant 1999;14:521-3.
5. O'Reilly RA. The stereoselective interaction of warfarin and metronidazole in man. N Engl J Med 1976;295:354-7.
6. Kazimer FJ. A significant interaction between metronidazole and warfarin. Mayo Clin Proc 1976;51:782-4.
7. Blyden GT, Scavone JM, Greenblatt DJ. Metronidazole impairs clearance of phenytoin but not of alprazolam or lorazepam. J Clin Pharmacol 1988;28:240-5.
8. Jensen JC, Gugler R. Interaction between metronidazole and drugs eliminated by oxidative metabolism. Clin Pharmacol Ther 1985;37:407-10.
9. Joshi JV, Joshi UM, Sankholi GM, et al. A study of interaction of low-dose combination oral contraceptive with ampicillin and metronidazole. Contraception 1980;22:643-52.
10. Wang JS, Backman JT, Kivisto KT, Neuvonen PJ. Effects of metronidazole on midazolam metabolism in vitro and in vivo. Eur J Clin Pharmacol 2000;56:555-9.
11. Hansten PD, Horn JT. Drug interactions analysis and management. St. Louis: Facts and Comparisons, 2000:214, 430.
12. Tatro DS, ed. Drug interaction facts. St. Louis: Facts and Comparisons, 1998:254, 355.
13. Lee C, Anderson RC, Chen KK. Distribution and excretion of radioactivity in rats receiving N-methyl-[14]C-erythromycin. J Pharmacol Exp Ther 1956;117:265-73.
14. Turgeon DK, Leichtman AB, Blake DS, et al. Prediction of interpatient and intrapatient variation in OG 37-325 dosing requirements by the erythromycin breath test. Transplantation 1994;57:1736-41.
15. Wagner D. CYP3A4 and the erythromycin breath test [letter]. Clin Pharmacol Ther 1998;64:129-30.
16. Watkins PB, Murray SA, Winkelman LG, Heuman DM, Wrighton SA, Guzelian PS. Erythromycin breath test as an assay of glucocorticoid-inducible liver cytochromes P-450. Studies in rats and patients. J Clin Invest 1989;83:688-97.
17. Watkins PB. Noninvasive tests of CYP3A enzymes. Pharmacogenetics 1994;4:171-84.
18. Lown K, Kolars J, Turgeon K, Merion R, Wrighton SA, Watkins PB. The erythromycin breath test selectively measures P450IIIA in patients with severe liver disease. Clin Pharmacol Ther 1992;51:229-38.
19. Watkins PB, Hamilton TA, Annesley TM, Ellis CN, Kolars JC, Voorhees JJ. The erythromycin breath test as a predictor of cyclosporine blood levels. Clin Pharmacol Ther 1990;48:120-9.
20. Turgeon DK, Normolle DP, Leichtman AB, Annesley TM, Smith DE, Watkins PB. Erythromycin breath test predicts oral clearance of cyclosporine in kidney transplant recipients. Clin Pharmacol Ther 1992;52:471-8.
21. Cheng CL, Smith DE, Carver PL, et al. Steady-state pharmacokinetics of delavirdine in HIV-positive patients: effect on erythromycin breath test. Clin Pharmacol Ther 1997; 61:531-43.
22. Jamis-Dow CA, Pearl ML, Watkins PB, Blake DS, Klecker RW, Collins JM. Predicting drug interactions in vivo from experiments in vitro. Human studies with paclitaxel and ketoconazole. Am J Clin Oncol 1997;20:592-9.
23. Polk RE, Crouch MA, Israel DS, et al. Pharmacokinetic interaction between ketoconazole and amprenavir after single doses in healthy men. Pharmacotherapy 1999;19:1378-84.
24. Brophy DF, Israel DS, Pastor A, et al. Pharmacokinetic interaction between amprenavir and clarithromycin in healthy male volunteers. Antimicrob Agents Chemother 2000;44: 978-84.
25. Reitberg DP, Klarnet JP, Carlson JK, Schentag JJ. Effect of metronidazole on theophylline pharmacokinetics. Clin Pharm 1983;2:441-4.
26. Adebayo GI, Mabadeje FB. Lack of inhibitory effect of metronidazole on theophylline disposition in healthy subjects. Br J Clin Pharmacol 1987;24:110-3.
27. Haas CE. Drug-cytokine interactions. In: Piscitelli SC, Rodvold KA, eds. Drug interactions in infectious diseases. Totowa, NJ: Humana Press, 2001:287-310.
28. Reiss WG, Piscitelli SC. Drug-cytokine interactions. mechanisms and clinical implications. BioDrugs 1998;9:389-95.
29. Fardel O, Lecureur V, Guillouzo A. The P-glycoprotein multidrug transporter. Gen Pharmacol 1996;27:1283-91.
30. Abernethy DR, Flockhart DA. Molecular basis of cardiovascular drug metabolism: implications for predicting clinically important drug interactions. Circulation 2000;101:1749-53.
31. Kim RB, Wandel C, Leake B, et al. Interrelationship between substrates and inhibitors of human CYP3A and P-glycoprotein. Pharm Res 1999;16:408-14.



Authors from: the Department of Pharmacy Practice, School of Pharmacy and Pharmaceutical Sciences, University at Buffalo, The State University of New York, Buffalo, New York (Drs. Haas and DiCenzo); and the Department of Surgery, University of Rochester Medical Center, Rochester, New York (Dr. Kaufman).
"

In reference to:


http://www.medscape.com/medline/abstract/7117297




Here's the abstract:

"
Stereochemical characterization of interactions of chiral 1,4-benzodiazepine-2-ones with liver microsomes.

Eur J Drug Metab Pharmacokinet. 1982; 7(2):137-46 (ISSN: 0398-7639)

Rendic S; Kajfez F

Microsomal P-450 cytochrome are stereoselective toward 7-Chloro-1,3-dihydro-3(S)-methyl-5-phenyl-2H-1,4-benzodiazepin-2-one. (S)-1, and 7-chloro-1,3-dihydro-3(S)-isopropyl-5-phenyl-2H-1,4-benzodiazepin-2-one, (S)-2. (S)-enantiomers bind to a substrate binding site which accomodates the stable M-conformation (Ks =0.01 to 0.018 mmol/l). (R)-enantiomers, however, undergo a ligand type of interaction (Ks = 0.036 to 0.12 mmol/l). Prochiral desmethyldiazepam behaves similarly to the (S)-enantiomers of the above compounds. The ligand binding site does not differentiate between M- and P-conformers.
"

As the technically inclined can see, this abstract would seem to imply or to suggest [I use these words very cautiously] at the very least the possibility of interactions arising from certain drugs and certain benzodiazepine derivatives [That 'methyl' expression seems quite interesting, doesn't it]. Of course that's only my opinion once more, not a fact.

And in reference to:


http://www.medscape.com/medline/abstract/12421359






Here's the abstract that I meant to share:

"
Study of the nematode putative GABA type-A receptor subunits: evidence for modulation by ivermectin.

J Neurochem. 2002; 83(4):870-8 (ISSN: 0022-3042)

Feng XP; Hayashi J; Beech RN; Prichard RK
Institute of Parasitology, McGill University, Quebec, Canada.

Two alleles of the HG1 gene, which encodes a putative GABA receptor alpha/gamma subunit, were isolated from Haemonchus contortus. These two alleles were shown previously to be associated with ivermectin susceptibility (HG1A) and resistance (HG1E), respectively. Sequence analysis indicates that they differ in four amino acids. To explore the functional properties of the two alleles, a full-length cDNA encoding the beta subunit, a key functional component of the GABA receptor, was isolated from Caenorhabditis elegans (gab-1, corresponding to the GenBank locus ZC482.1) and coexpressed in Xenopus oocytes with the HG1 alleles. When gab-1 was coexpressed with either the HG1A allele or the HG1E allele in Xenopus oocytes, gamma-aminobutyric acid (GABA)-responsive channels with different sensitivity to the agonist were formed. The effects of ivermectin on the hetero-oligomeric receptors were determined. Application of ivermectin alone had no effect on the receptors. However, when coapplied with 10 micro m GABA, ivermectin potentiated the GABA-evoked current of the GAB-1/HG1A receptor, but attenuated the GABA response of the GAB-1/HG1E receptor. We demonstrated that the coexpressed HG1 and GAB-1 receptors are GABA-responsive, and provide evidence for the possible involvement of GABA receptors in the mechanism of ivermectin resistance.
"

.. Which states clearly that GABA receptors are found INSIDE helminths too:

Read this part:
"
a full-length cDNA encoding the beta subunit, a key functional component of the GABA receptor, was isolated from Caenorhabditis elegans (gab-1, corresponding to the GenBank locus ZC482.1) and coexpressed in Xenopus oocytes with the HG1 alleles.
"

At least inside Caenorhabditis elegans, a 'role-model' worm widely used in research and study, according to my knowledge and to sources:

"
Caenorhabditis elegans (IPA: [ˌsiːnəʊræbˈdaɪtɪs ˈelegænz]) is a free-living nematode (roundworm), about 1 mm in length, which lives in temperate soil environments. Research into the molecular and developmental biology of C. elegans was begun in 1974 by Sydney Brenner [1] and it has since been used extensively as a model organism.
"


http://en.wikipedia.org/wiki/Caenorhabditis_elegans



"
Caenorhabditis elegans is a small (about 1 mm long) soil nematode found in temperate regions. In the 1960's Sydney Brenner began using it to study the genetics of development and neurobiology. Since then the community of C elegans researchers has expanded several thousands. See Mark Blaxter's The Genetics of Caenorhabditis elegans, An Introduction for more information.
"


http://elegans.swmed.edu/




Thanks, Medscape.

Hi Rabbitears. I just wanted to clarify what I meant by euphoric state. This was due to a complete "switching" from pathogenic state to healthy state. The 'flushing' of foriegn substance from body via urine, was evidence the immune-system went into full action. It was the state of healthiness which created the "euphoria". But, the body needs time to re-adjust and this is what caused sleeplessness.
It will be a matter of time before research scientists stumble on to this mechanism.
It may not be the benzodiazepines, but the area of the brain and the interconnectivity of neuro-receptors ect. will be discovered as a way to "reboot" the immune-responses. Shroom