摘要:

In recent years, drug analysis in keratinised matrices, such as hair and nails, has received considerable attention because of several advantages over drug testing methodologies employing body fluids, such as urine or serum. For example, keratinic matrices, such as finger- and toenails, can accumulate drugs during long term exposure. Drugs are incorporated into nails by a double mechanism:deposition into the root of the growing nail via the blood flow in the nail matrix; andincorporation via the nail bed during growth from the lunula to the beginning of the free margin. Together, these account for a wide retrospective window of drug detection.Nails can provide a good forensic matrix for the detection of drugs of abuse. Indeed, the international literature has reported the use of nail analysis in post-mortem detection of drugs of abuse, drug testing in the workplace and drug screening to detect prenatal exposure, even though further studies are needed for correct interpretation of the data obtained.Another application of drug analysis in nails consists of the possibility of detecting the presence of an antimycotic at the site of action during antifungal therapy for patients with onychomycosis. When available, this evidence has permitted drug treatment of a shorter duration and reduced toxicity. However, so far the potential of drug monitoring in nails still lacks harmonisation and validation of analytical methodologies and a better comprehension of the possible correlation between drug concentrations in the matrix and period of exposure.

ISSN:0312-5963    

出版商:ADIS    

年代:2000

数据来源: ADIS

摘要:

This article reviews the metabolic pharmacokinetic drug-drug interactions with the systemic antifungal agents: the azoles ketoconazole, miconazole, itraconazole and fluconazole, the allylamine terbinafine and the sulfonamide sulfamethoxazole. The majority of these interactions are metabolic and are caused by inhibition of cytochrome P450 (CYP)-mediated hepatic and/or small intestinal metabolism of coadministered drugs.Human liver microsomal studiesin vitro, clinical case reports and controlled pharmacokinetic interaction studies in patients or healthy volunteers are reviewed. A brief overview of the CYP system and the contrasting effects of the antifungal agents on the different human drug-metabolising CYP isoforms is followed by discussion of the role of P-glycoprotein in presystemic extraction and the modulation of its function by the antifungal agents. Methods used forin vitrodrug interaction studies andin vitro−in vivoscaling are then discussed, with specific emphasis on the azole antifungals.Ketoconazole and itraconazole are potent inhibitors of the major drug-metabolising CYP isoform in humans, CYP3A4. Coadministration of these drugs with CYP3A substrates such as cyclosporin, tacrolimus, alprazolam, triazolam, midazolam, nifedipine, felodipine, simvastatin, lovastatin, vincristine, terfenadine or astemizole can result in clinically significant drug interactions, some of which can be life-threatening. The interactions of ketoconazole with cyclosporin and tacrolimus have been applied for therapeutic purposes to allow a lower dosage and cost of the immunosuppressant and a reduced risk of fungal infections. The potency of fluconazole as a CYP3A4 inhibitor is much lower. Thus, clinical interactions of CYP3A substrates with this azole derivative are of lesser magnitude, and are generally observed only with fluconazole dosages of ≥200 mg/day.Fluconazole, miconazole and sulfamethoxazole are potent inhibitors of CYP2C9. Coadministration of phenytoin, warfarin, sulfamethoxazole and losartan with fluconazole results in clinically significant drug interactions. Fluconazole is a potent inhibitor of CYP2C19in vitro, although the clinical significance of this has not been investigated. No clinically significant drug interactions have been predicted or documented between the azoles and drugs that are primarily metabolised by CYP 1A2, 2D6 or 2E1.Terbinafine is a potent inhibitor of CYP2D6 and may cause clinically significant interactions with coadministered substrates of this isoform, such as nortriptyline, desipramine, perphenazine, metoprolol, encainide and propafenone. On the basis of the existingin vitroandin vivodata, drug interactions of terbinafine with substrates of other CYP isoforms are unlikely.

ISSN:0312-5963    

出版商:ADIS    

年代:2000

数据来源: ADIS

摘要:

Drug delivery by target-controlled infusion (TCI) allows automatic adjustments of the infusion rate of a drug to maintain a desired target concentration. Since drug effect is more closely related to blood concentration than to infusion rate, drug delivery via TCI is capable of creating stable blood concentrations of intravenous anaesthetics and analgesics.In this article the concept and history of TCI are described. The rational administration of TCI requires an appropriate pharmacokinetic data set and knowledge of the concentration-effect relationship; therefore, general pharmacokinetic and pharmacodynamic aspects of intravenous anaesthetics and analgesics are also addressed. Intraoperative investigations have demonstrated that TCI drug delivery allows rapid titration to a desired effect. The use of TCI for postoperative analgesia is still experimental, but TCI can, in part, overcome the disadvantages associated with continuous infusions and patient-controlled analgesia regimens in the postoperative period.Although TCI is capable of creating stable blood concentrations, when the target concentration is changed the resulting effect correlates better with a theoretical effect site concentration. The efficacy of TCI systems that can perform effect-site steering are still to be explored.

ISSN:0312-5963    

出版商:ADIS    

年代:2000

数据来源: ADIS