Effect of metoclopramide and loperamide on the pharmacokinetics of didanosine in HIV seropositive asymptomatic male and female patients

MSBIS: A Multi-Step Biomedical Informatics Screening Approach for Identifying Medications that Mitigate the Risks of Metoclopramide-Induced Tardive Dyskinesia

In 2009 the U.S. Food and Drug Administration (FDA) placed a black box warning on metoclopramide (MCP) due to the increased risks and prevalence of tardive dyskinesia (TD). In this study, we developed a multi-step biomedical informatics screening (MSBIS) approach leveraging publicly available bioactivity and drug safety data to identify concomitant drugs that mitigate the risks of MCP-induced TD. MSBIS includes (1) TargetSearch (http://dxulab.org/software) bioinformatics scoring for drug anticholinergic activity using CHEMBL bioactivity data; (2) unadjusted odds ratio (UOR) scoring for indications of TD-mitigating effects using the FDA Adverse Event Reporting System (FAERS); (3) adjusted odds ratio (AOR) re-scoring by removing the effect of cofounding factors (age, gender, reporting year); (4) logistic regression (LR) coefficient scoring for confirming the best TD-mitigating drug candidates. Drugs with increasing TD protective potential and statistical significance were obtained at each screening step. Fentanyl is identified as the most promising drug against MCP-induced TD (coefficient: −2.68; p-value < 0.01). The discovery is supported by clinical reports that patients fully recovered from MCP-induced TD after fentanyl-induced general anesthesia. Loperamide is identified as a potent mitigating drug against a broader range of drug-induced movement disorders through pharmacokinetic modifications. Using drug-induced TD as an example, we demonstrated that MSBIS is an efficient in silico tool for unknown drug-drug interaction detection, drug repurposing, and combination therapy design.

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An in silico MSBIS approach was developed to identify concomitant drugs that mitigate the side effects of a primary drug.

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Fentanyl and loperamide were identified to protect patients against drug-induced tardive dyskinesia (TD).

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MSBIS can be generalized to provide rational starting points for drug repurposing and combination therapy design.

Many dopamine antagonists cause TD and other severe, irreversible movement disorders. 120 drugs were screened using the MSBIS approach, leading to the discovery of fentanyl and loperamide. When co-administered with dopamine antagonists such as metoclopramide, they may protect patients against drug-induced movement disorders including TD. Their mechanisms of toxicity-mitigating action are remarkably different. The statistical significance of the findings was established using the FDA Adverse Event Reporting System and supported by published clinical reports and pharmacologic data. This study demonstrated the feasibility of the MSBIS approach and its applicability in identifying unknown drug-drug interactions that either mitigate undesirable toxicities or synergize therapeutic effects.

Decreased dopaminergic tone and increased basal bioactive prolactin in men with human immunodeficiency virus infection

OBJECTIVE

The aims of the study were: (1) to assess dopaminergic tone in a group of HIV infected men and the bioactivity and the molecular species of their circulating PRL in comparison with healthy men and (2) to search for a correlation between serum PRL and CD4+ T lymphocytes and viral load.

DESIGN

In a cross-sectional study the effect of acute dopaminergic blockade with intravenous metoclopramide on serum PRL (both immunoreactive and biologically active), TSH and PRL circulating molecular isoforms was evaluated.

PATIENTS

Twenty untreated HIV infected men category C2 or C3, mean (SD) age 26.9 (6.3) years, were compared to 14 clinically healthy HIV-negative men, age 25.4 (2.3) years.

MEASUREMENTS

Under fasting conditions and following metoclopramide administration duplicate measurements of serum immunoreactive PRL, bioactive PRL (PRL dependent Nb2 lymphoma cell assay) and immunoreactive TSH were performed. The molecular species of circulating PRL were determined by immunoblot analysis, CD4+ T lymphocytes by flow cytometry and the viral load using a nucleic acid sequence-based amplification assay.

RESULTS

In HIV infected men fasting bioactive (but not immunoreactive) PRL was higher (P = 0.03), but the stimulated PRL (both immunoreactive and bioactive) was lower than in healthy men throughout the test (P < or = 0.01). Fasting serum TSH was similar in HIV-infected and healthy men while its response to metoclopramide was absent in the former but not in the latter (P = 0.049). A 23.5-kD PRL was the predominant circulating isoform both in patients and healthy men. Considering HIV-infected and healthy men, CD4+ T lymphocytes correlated negatively with fasting bioactive PRL (P = 0.008) and positively with the area under the PRL (both immunoreactive and bioactive) curves (P < 0.001). The viral load was negatively correlated with the area under the curve of the bioactive/immunoreactive ratio (P = 0.008).

CONCLUSIONS

The raised fasting bioactive PRL, the diminished response of both immunoreactive and bioactive PRL and the absent TSH response to metoclopramide in HIV infected men, suggest the existence of a decreased, but not absent dopaminergic tone. A monomeric form of PRL was the predominant circulating species, as in healthy men, and this hormone seems to be associated both with CD4+ T lymphocytes and the viral load.

Evaluation of a fluorogenic derivatization method for the reversed-phase HPLC analysis of 2'-beta-fluoro-2',3'-dideoxyadenosine, a new anti-AIDS drug

High sensitivity (10(-7) to 10(-9) M) reversed-phase high-performance liquid chromatography (HPLC) analysis of adenine nucleosides and nucleotides, especially in a biological matrix, is difficult using only ultraviolet detection. Derivatization coupled with fluorescence detection has been investigated as a means of enhancing sensitivity for the reversed-phase HPLC analysis of 2'-beta-fluoro-2',3'-dideoxyadenosine (F-ddA), an experimental, acid-stable, anti-AIDS drug. The reaction of chloroacetaldehyde with the adenine base has been employed to form fluorescent 1,N(6)-etheno derivatives of F-ddA and 5'-deoxyadenosine, which is used as an internal standard. These derivatives give an analytically useful fluorescence emission at 416 nm after excitation at 230, 265, or 275 nm. Derivatization, fluorescence detection and reversed-phase chromatography have been optimized for the analysis of nanomolar concentrations of F-ddA in human plasma. This method has potential for the measurement of F-ddA at low concentration and in limited volume samples from in vivo biological studies.

Effect of altered gastric emptying and gastrointestinal motility on metformin absorption

AIMS

The purpose of this in vivo human study was to assess the effect of altered gastric emptying and gastrointestinal motility on the absorption of metformin in healthy subjects.

METHODS

An open-label, three treatment, three period crossover study was conducted in 11 healthy volunteers. Each subject received 550 mg metformin hydrochloride in solution alone; 5 min after a 10 mg i.v. dose of metoclopramide; and 30 min after a 30 mg oral dose of propantheline. Metformin solution was radiolabeled by the addition of 99mTc-DTPA. The gastrointestinal transit of the solution was monitored by gamma scintigraphy and the pharmacokinetic data were correlated with the scintigraphic findings.

RESULTS

Scintigraphic data indicated that pretreatment with metoclopramide decreased gastric emptying time and increased gastrointestinal motility while pretreatment with propantheline had the opposite effect. The systemic disposition of metformin was not altered by pretreatment with metoclopramide and propantheline, as judged by unchanged renal clearance and elimination half-life of metformin. Extent of metformin absorption was essentially unchanged after pretreatment with metoclopramide. However, AUC(0,infinity) and % UR (percent dose excreted unchanged in urine) generally increased with increase in gastric emptying time and small intestinal transit times. GI overlay plots showed that the absorption phase of metformin plasma profile always coincided with gastric emptying and the beginning of decline of metformin plasma concentrations was usually associated with the colon arrival. Only in cases where the intestinal transit was drastically prolonged by propantheline pretreatment, was a decline in plasma levels observed prior to colon arrival.

CONCLUSIONS

Metformin is primarily absorbed from the small intestine. The extent of metformin absorption is improved when the gastrointestinal motility is slowed. These findings have significant implications in the design of a metformin modified release dosage form.

Differences between women and men in adverse events and CD4+ responses to nucleoside analogue therapy for HIV infection. The Aids Clinical Trials Group 175 Team

OBJECTIVE

To prospectively examine differences in baseline characteristics and study outcomes between HIV-infected women and men during a clinical trial of nucleoside analogue therapy.

METHODS

ACTG 175 randomized HIV-infected patients with CD4+ counts between 200 and 500 cells/mm3 to one of four nucleoside analogue regimens: zidovudine (ZDV), didanosine (ddI), ZDV + ddI, or ZDV + zalcitabine (ddC). Differences in time to first dose modification, voluntary withdrawal, development of toxicity and symptomatology, and AIDS progression were compared by gender.

RESULTS

The study included 438 women and 2029 men. Baseline values of HIV RNA plasma concentrations were significantly lower for women (0.3 log10) than men in a subset of patients in whom assays were taken and this difference persisted after adjustment for CD4+ count. Women reported reducing dosage and discontinue ddI-containing regimens more frequently than men did; adjustment for weight did not completely explain this difference. Women were at lower risk than men for progression to a study endpoint (19% of women versus 24% of men; p <.0001). Among those antiretroviral-naive study subjects receiving ZDV, men were four times more likely to progress to a study endpoint than women.

CONCLUSIONS

Differences in pretreatment characteristics and on study experiences were demonstrated between women and men enrolled in this clinical trial. The suggestion of a gender difference in response to ZDV monotherapy by antiretroviral-naive study subjects and the lower baseline values for HIV RNA in women compared with those in men provides evidence for gender differences in the relationship between virus replication, CD4+ decline, and responses to nucleoside analogue therapy.

Quantitation of loperamide and N-demethyl-loperamide in human plasma using electrospray ionization with selected reaction ion monitoring liquid chromatography-mass spectrometry

We report here the development and validation of an LC-MS method for quantitation of loperamide (LOP) and its N-demethyl metabolite (DMLOP) in human plasma. O-Acetyl-loperamide (A-LOP) was synthesized by us for use as an internal standard in the assay. After addition of the internal standard, the compounds of interest were extracted with methyl tert.-butylether and separated by HPLC on a C18 reversed-phase column using an acetonitrile-water gradient containing 20 mM ammonium acetate. The three compounds were well separated by HPLC and no interfering peaks were detected at the usual concentrations found in plasma. Analytes were quantitated using positive electrospray ionization in a triple quadrupole mass spectrometer operating in the MS-MS mode. Selected reaction monitoring was used to quantify LOP (m/z 477-266), DMLOP (m/z 463-->252) and A-LOP (m/z 519-->266) on ions formed by loss of the 4-(p-chlorophenyl)-4-hydroxy-piperidyl group upon low energy collision-induced dissociation. Calibration curves, which were linear over the range 1.04 to 41.7 pmol/ml (LOP) and 1.55 to 41.9 pmol/ml (DMLOP), were run contemporaneously with each batch of samples, along with low (4.2 pmol/ml), medium (16.7 pmol/ml) and high (33.4 pmol/ml) quality control samples. The lower limit of quantitation (LLQ) of LOP and DMLOP was about 0.25 pmol/ml in plasma. The extraction efficiency of LOP and DMLOP from human plasma was 72.3+/-1.50% (range: 70.7-73.7%) and 79.4+/-12.8% (64.9-88.8%), respectively. The intra- and inter-assay variability of LOP and DMLOP ranged from 2.1 to 14.5% for the low, medium and high quality control samples. The method has been used successfully to study loperamide pharmacokinetics in adult humans.

The uncoupled couple? Prolactin and CD4 lymphocytes in HIV infection

The possible role of prolactin (PRL) in human immunodeficiency virus (HIV) infection is unknown, despite the modulatory role of this hormone in humoral and cell-mediated immune responses. Recent studies have evidenced: (a) intralymphocyte synthesis of dopamine (DA) which down-regulates their own proliferation and differentiation; (b) decreased DA but increased PRL concentrations in cerebrospinal fluid of HIV-infected men; and (c) diminished hypothalamic DA tone in HIV-infected men. The present hypothesis proposes that, in HIV-infected men, a diminished generalized DA tone exists to stimulate human lymphocyte proliferation and differentiation at a maximum possible rate by: (1) decreasing the inhibitory influence of intralymphocyte DA; and (2) maintaining pituitary and extrapituitary (i.e. lymphocyte) PRL synthesis and release as high as possible. If this hypothesis is correct, it may have a potentially important therapeutic implication: the possibility to rebuild the battered immune system in HIV-infected patients from inside the body in a physiologic manner by the parenteral administration of recombinant human PRL.

Impaired metoclopramide-induced pituitary prolactin release in men with human immunodeficiency virus infection

To investigate whether metoclopramide-induced prolactin release is impaired in HIV-infected men, we studied 10 clinically healthy HIV-negative adult men (group 1) and 10 consecutive HIV-positive adult men (group 2) with anti-HIV antibodies confirmed by Western blot analysis and a CD4 cell count from 13 to 570x10(6)/L. After a 10- to 12-hour overnight fast, three basal blood samples were obtained at 15-minute intervals (-30, -15, and 0 minutes) and thereafter at 15, 30, 60, 90, 120, 180, and 240 minutes after a 10-mg intravenous bolus of metoclopramide. Duplicate serum prolactin concentrations were measured in each sample with commercially available radioimmunoassay kits. No significant differences between groups were observed in basal prolactin levels. Group 2 had lower serum prolactin concentrations than group 1 throughout the test (P< or =.002). The area under the prolactin curve (mean +/- SD) was also lower in group 2 than in group 1 (7156+/-1433 ng/mL/240 min vs. 12430+/-2454 ng/mL/240 min, P<.0001), and the area under the prolactin curve had a significant correlation with the CD4 cell counts (r = 0.7912, P<.001). These findings suggest that the hypothalamic dopaminergic tone, although present, was clearly diminished in these HIV-positive men regardless of their clinical stage.

Effect of fluconazole on pharmacokinetics of 2',3'-dideoxyinosine in persons seropositive for human immunodeficiency virus

Fluconazole inhibits cytochrome P-450-mediated enzymatic metabolism of several drugs. Since hepatic metabolism is partially responsible for 2',3'-dideoxyinosine (didanosine or ddI) elimination, fluconazole therapy may lead to increased ddI concentrations in serum and subsequent concentration-dependent adverse effects. The purpose of this study was to determine if ddI pharmacokinetics are influenced by a 7-day course of oral fluconazole. Twelve adults with human immunodeficiency virus (HIV) who had received a constant dosage of ddI for at least 2 weeks were investigated. On study day 1, multiple serum samples for determination of ddI concentrations were obtained over 12 h. Then subjects received a 7-day course of oral fluconazole (200 mg every 12 h for two doses and then 200 mg once daily for 6 days) while ddI therapy continued. Following the last dose of fluconazole, serum samples for determination of ddI concentrations were again obtained over 12 h. ddI concentrations in serum were analyzed by radioimmunoassay. In contrast to previously published data, there was marked between-subject variability in ddI areas under the concentration-time curve, even when the dose was normalized for weight. No significant differences were found between mean ddI areas under the concentration-time curve from 0 to 12 h on study day 1 (1,528 +/- 902 ngx.hr/ml) and following fluconazole treatment (1,486 +/- 649 ngx.hr/ml) . There were no significant differences in other pharmacokinetic parameters, such as ddI peak concentrations in serum (971 +/- 509 and 942 +/- 442 ng/ml) or half-lives (80 +/- 32 and 85 +/- 21 min.) before and after fluconazole treatment, respectively. We conclude that a 7-day course of oral fluconazole does not significantly alter ddI pharmacokinetics in adults that are infected with human immunodeficiency virus.