Lack of fluconazole effects on human chemosensation.

OBJECTIVE: Drug effects on the function of smell and taste are occasionally mentioned in prescription information however, most originate from anecdotal reports without even distinguishing between gustatory or olfactory deteriorations. This includes the antifungal fluconazole. MATERIAL AND METHODS: In a randomized, placebo-controlled, double-blind, two-way crossover study, 12 healthy men and 9 healthy women (age 26.8 ± 3.7 years) took oral doses of 400 mg fluconazole or placebo once daily for 8 days. Gustatory and olfactory functions were tested before and after the treatment using clinically validated tests ("Taste Strips" and "Sniffin' Sticks", respectively). RESULTS: Baseline taste scores of 12.3 ± 2.2 and 12.5 ± 1.7 for the fluconazole and placebo conditions, respectively, corresponded to normative values. Similarly, baseline (pretreatment) composite olfactory TDI scores (odor "€œthreshold discrimination identification"€) of 35.0 ± 3.2 and 35.7 ± 4.3 for men and 34.8 ± 4.2 and 35.5 ± 2.8 for women during the fluconazole or placebo conditions, respectively, corresponded to normative values. Neither gustation nor olfaction was significantly affected by the fluconazole treatment. CONCLUSIONS: The present study provided a negative result regarding fluconazole effects contrasting, for example, with those of sildenafil in a comparatively powered study [1]. Up to the tested dose of 400 mg/d, fluconazole does not have general and reproducible effects on taste and smell in healthy humans. However, it was unlikely to detect rare disturbances with the present study cohort size, and, therefore, rare fluconazole side effects on human chemosensation, as occasionally reported, remain a possibility.

Chronic opioid use is associated with increased DNA methylation correlating with increased clinical pain.

Environmentally caused changes in chromosomes that do not alter the DNA sequence but cause phenotypic changes by altering gene transcription are summarized as epigenetics. A major epigenetic mechanism is methylation or demethylation at CpG-rich DNA islands. DNA methylation triggered by drugs has largely unexplored therapeutic consequences. Here we report increased methylation at a CpG rich island in the OPRM1 gene coding for µ-opioid receptors and at a global methylation site (LINE-1) in leukocytes of methadone-substituted former opiate addicts compared with matched healthy controls. Higher DNA methylation associated with chronic opioid exposure was reproduced in an independent cohort of opioid-treated as compared to non-opioid-treated pain patients. This suggests that opioids may stimulate DNA methylation. The OPRM1 methylation had no immediate effect on µ-opioid receptor transcription and was not associated with opioid dosing requirements. However, the global DNA methylation at LINE-1 was significantly correlated with increased chronic pain. This suggests inhibitory effects on the transcription of still unspecified nocifensive gene products. It further implies that opioids may be causally associated with increased genome-wide DNA methylation, although currently there is no direct evidence of this. This has phenotypic consequences for pain and may provide a new, epigenetics-associated mechanism of opioid-induced hyperalgesia. The results indicate a potential influence of opioid analgesics on the patients' epigenome. They emphasize the need for reliable and cost-effective screening tools and may imply that high-throughput screening for lead compounds in artificial expression systems may not provide the best tools for identifying new pain medications.

Clinical pharmacology of analgesics assessed with human experimental pain models: bridging basic and clinical research.

The medical impact of pain is such that much effort is being applied to develop novel analgesic drugs directed towards new targets and to investigate the analgesic efficacy of known drugs. Ongoing research requires cost-saving tools to translate basic science knowledge into clinically effective analgesic compounds. In this review we have re-examined the prediction of clinical analgesia by human experimental pain models as a basis for model selection in phase I studies. The overall prediction of analgesic efficacy or failure of a drug correlated well between experimental and clinical settings. However, correct model selection requires more detailed information about which model predicts a particular clinical pain condition. We hypothesized that if an analgesic drug was effective in an experimental pain model and also a specific clinical pain condition, then that model might be predictive for that particular condition and should be selected for development as an analgesic for that condition. The validity of the prediction increases with an increase in the numbers of analgesic drug classes for which this agreement was shown. From available evidence, only five clinical pain conditions were correctly predicted by seven different pain models for at least three different drugs. Most of these models combine a sensitization method. The analysis also identified several models with low impact with respect to their clinical translation. Thus, the presently identified agreements and non-agreements between analgesic effects on experimental and on clinical pain may serve as a solid basis to identify complex sets of human pain models that bridge basic science with clinical pain research.

Necessity and risks of arterial blood sampling in healthy volunteer studies.

Arterial blood sampling is necessary when drugs such as the fast-acting opioid analgesic remifentanil exhibit relevant differences between arterial and venous blood concentrations. Arterial cannulation is generally considered to be clinically safe and has thus become a standard procedure in pharmacokinetic-pharmacodynamic assessments. However, rare cases of arterial occlusions have to be considered in risk-benefit assessments of arterial sampling in pharmacokinetic studies, especially when including healthy volunteers. In an actual case, arterial occlusion requiring surgical repair was caused by a factor V Leiden thrombophilia associated genetic variant F5 1691G>A (rs6025) and aggravated by a hypoplastic radial artery. Neither risk factor had been identified prior to enrolment by routine laboratory tests such as the prothrombin time (international normalized ratio), partial thromboplastin time and the clinical Allen's test of arterial function. Re-assessment of the necessity of arterial sampling showed that none of the potential alternatives, target concentrations of computerized infusions or venous concentrations during non-steady-state and steady-state conditions could provide the arterial concentrations. Relying on venous concentrations may result in erroneous pharmacodynamic parameters. Accurate pharmacokinetic-pharmacodynamic studies relying on precisely measured blood concentrations require serial sampling techniques during both steady-state and non-steady-state conditions. However, as illustrated by the presented case, incidents involving the generally safe procedure of arterial sampling are possible, although rare. To further minimize the risks, screening of subjects for prothrombotic risks and careful assessment of the suitability of the artery should be considered in pharmacokinetic studies requiring arterial cannulation.

A common human micro-opioid receptor genetic variant diminishes the receptor signaling efficacy in brain regions processing the sensory information of pain.

The single nucleotide polymorphism 118A>G of the human micro-opioid receptor gene OPRM1, which leads to an exchange of the amino acid asparagine (N) to aspartic acid (D) at position 40 of the extracellular receptor region, alters the in vivo effects of opioids to different degrees in pain-processing brain regions. The most pronounced N40D effects were found in brain regions involved in the sensory processing of pain intensity. Using the mu-opioid receptor-specific agonist DAMGO, we analyzed the micro-opioid receptor signaling, expression, and binding affinity in human brain tissue sampled postmortem from the secondary somatosensory area (SII) and from the ventral posterior part of the lateral thalamus, two regions involved in the sensory processing and transmission of nociceptive information. We show that the main effect of the N40D micro-opioid receptor variant is a reduction of the agonist-induced receptor signaling efficacy. In the SII region of homo- and heterozygous carriers of the variant 118G allele (n=18), DAMGO was only 62% as efficient (p=0.002) as in homozygous carriers of the wild-type 118A allele (n=15). In contrast, the number of [3H]DAMGO binding sites was unaffected. Hence, the micro-opioid receptor G-protein coupling efficacy in SII of carriers of the 118G variant was only 58% as efficient as in homozygous carriers of the 118A allele (p<0.001). The thalamus was unaffected by the OPRM1 118A>G SNP. In conclusion, we provide a molecular basis for the reduced clinical effects of opioid analgesics in carriers of mu-opioid receptor variant N40D.

Modulation of the central nervous effects of levomethadone by genetic polymorphisms potentially affecting its metabolism, distribution, and drug action.

AIM: Our aim was to judge the importance of candidate pharmacogenetic modulators of the central nervous effects of levomethadone by both magnitude of the modulatory effect and frequency of the mutation to assess the utility of genotyping for clinical levomethadone therapy in a random sample of subjects that, by distribution of genotypes, resembled the clinical setting. METHODS: Candidate pharmacogenetic modulators were polymorphisms reported to be of functional consequence and therefore potentially important for metabolism, distribution, or pharmacodynamic action of levomethadone, consisting of genes coding for cytochrome P450 (CYP) 2B6 and 3A, as well as 1A2, 2C8, 2C9, 2C19, and 2D6, for P-glycoprotein (ABCB1), and for mu-opioid receptors (OPRM1). The central nervous effects of levomethadone were investigated by means of measuring pupil size in a random sample of 51 healthy volunteers for 9 hours after oral administration of 0.075 mg/kg levomethadone. Plasma concentrations of levomethadone and its metabolites were assessed concomitantly, and to judge the role of metabolites, the affinities of levomethadone and its metabolites at mu-opioid receptors were estimated by use of displacement of the selective mu-opioid receptor agonist [(3)H]-DAMGO ((3)H-[D-Ala(2),N-MePhe(4),Gly-ol(5)]-enkephalin). RESULTS: Pupil size decreased to -41.8% +/- 9.6% from baseline at 3.5 +/- 1.1 hours after levomethadone administration. Miosis was still manifest to a lower degree (-25.1% +/- 12.3%) at the end of the observation period. In carriers of the variant 118G allele (118A>G single-nucleotide polymorphism) of the mu-opioid receptor gene (OPRM1), levomethadone had a 1.74 times (95% confidence interval, 1.4-2.2 times) lower miotic potency (P < .001) as compared with noncarriers (concentration at half-maximum effects, 52.3 nmol/L; 95% confidence interval, 36.7-66.2 nmol/L). The maximum percent decrease in pupil diameter from baseline was 44.9% +/- 7.6%, 33% +/- 6.5%, and 24% +/- 6.9% for carriers of the OPRM1 118AA, AG, and GG genotypes, respectively (P < .001 for AG and GG versus wild type, without significant differences between AG and GG). Other candidate polymorphisms in the ABCB1 or in CYP genes had no significant influence on the effects of levomethadone, either because of lack of functional consequences or because of their low allelic frequency. The metabolites of levomethadone did not contribute to the effects as indicated by low metabolite plasma concentrations and their 120- to 1300-fold lower affinities at mu-opioid receptors as compared with levomethadone. CONCLUSIONS: Among polymorphisms in OPRM1, ABCB1, and CYP genes previously associated with functional consequences in a different context, the most important pharmacogenetic factor modulating the short-term effects of levomethadone is a polymorphism (OPRM1 118A>G) affecting mu-opioid receptors.