UMLS:C0019693 - FACTA Search

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Query: UMLS:C0019693 (HIV)
170,526 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

There are 3 groups of drugs available for the treatment of patients with HIV disease. These are the nucleoside reverse transcriptase inhibitors ('nucleoside analogues') [zidovudine, didanosine, zalcitabine, lamivudine and abacavir]; the non-nucleoside reverse transcriptase inhibitors (nevirapine, delavirdine and efavirenz); and the protease inhibitors (saquinavir, ritonavir, indinavir, nelfinavir and amprenavir). The preferred initial regimen should reduce and maintain plasma HIV RNA below the level of detection. Presently, the regimen of choice consists of 2 nucleoside analogues plus a protease inhibitor with high in vivo efficacy. An alternative combination consists of 2 nucleoside analogues plus a non-nucleoside reverse transcriptase inhibitor. Drug interactions are one of the major problems associated with these multidrug regimens. Changes in plasma concentrations of the nucleoside analogues are unlikely to be of clinical relevance as drug effect is mainly dependent on the rate and extent of intracellular phosphorylation. Combinations of zidovudine plus stavudine, and probably zalcitabine plus lamivudine, should be avoided as competition for phosphorylating enzymes may occur. The antiviral efficacy of some nucleoside analogues, e.g. stavudine, may be compromised by prior treatment with other nucleosides (e.g. zidovudine). However, these data need to be clarified in further studies. It is unlikely that administration of other antiretrovirals will influence the activity of nucleoside analogues. Protease inhibitors are metabolised by hepatic cytochrome P450 (CYP) 3A4. Combination protease inhibitor therapy can result in drug interactions mediated by enzyme inhibition. Ritonavir is the most potent inhibitor, saquinavir the least. The protease inhibitors also interact with the non-nucleoside reverse transcriptase inhibitors. Nevirapine and efavirenz induce drug metabolising enzymes and may reduce plasma concentrations of protease inhibitors. A study in healthy volunteers showed that nelfinavir concentrations are increased by combination with efavirenz. Delavirdine inhibits drug metabolising enzymes and increases the plasma concentration of coadministered protease inhibitors. The nucleoside analogues would not be expected to interact with the protease inhibitors. Apart from the ability of didanosine to reduce the area under the concentration-time curve of delavirdine, there are no reports of clinically significant interactions of other antiretrovirals with the non-nucleoside reverse transcriptase inhibitors. Triple therapy is the current standard of care for patients with HIV disease. However, studies of quadruple therapy are already under way. Drug interactions are likely to remain one of the major considerations when selecting a therapeutic regimen for patients with HIV.
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PMID:Pharmacokinetics and potential interactions amongst antiretroviral agents used to treat patients with HIV infection. 1032 Sep 51

ABT-378 is a potent in vitro inhibitor of the HIV protease and is currently being developed for coadministration with another HIV protease inhibitor, ritonavir, as an oral therapeutic treatment for HIV infection. In the present study, the effect of ritonavir, a potent inhibitor of cytochrome P-450 (CYP) 3A, on the in vitro metabolism of ABT-378 was examined. Furthermore, the effect of ABT-378-ritonavir combinations on several CYP-dependent monooxygenase activities in human liver microsomes was also examined. ABT-378 was found to undergo NADPH- and CYP3A4/5-dependent metabolism to three major metabolites, M-1 (4-oxo) and M-3/M-4 (4-hydroxy epimers), as well as several minor oxidative metabolites in human liver microsomes. The mean apparent K(m) and V(max) values for the metabolism of ABT-378 by human liver microsomes were 6.8 +/- 3.6 microM and 9.4 +/- 5.5 nmol of ABT-378 metabolized/mg protein/min, respectively. Ritonavir inhibited human liver microsomal metabolism of ABT-378 potently (K(i) = 0.013 microM). The combination of ABT-378 and ritonavir was much weaker in inhibiting CYP-mediated biotransformations than ritonavir alone, and the inhibitory effect appears to be primarily due to the ritonavir component of the combination. The ABT-378-ritonavir combinations (at 3:1 and 29:1 ratios) inhibited CYP3A (IC(50) = 1.1 and 4.6 microM), albeit less potently than ritonavir (IC(50) = 0.14 microM). Metabolic reactions mediated by CYP1A2, CYP2A6, and CYP2E1 were not affected by the ABT-378-ritonavir combinations. The inhibitory effects of ABT-378-ritonavir combinations on CYP2B6 (IC(50) = >30 microM), CYP2C9 (IC(50) = 13.7 and 23.0 microM), CYP2C19 (IC(50) = 28.7 and 38.0 microM), and CYP2D6 (IC(50) = 13.5 and 29.0 microM) were marginal and are not likely to produce clinically significant drug-drug interactions.
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PMID:Potent inhibition of the cytochrome P-450 3A-mediated human liver microsomal metabolism of a novel HIV protease inhibitor by ritonavir: A positive drug-drug interaction. 1042 17

The secreted aspartyl proteinase (Sap) of Candida albicans, which is believed to represent an important virulence factor of this opportunistic yeast, and the human immunodeficiency virus type 1 (HIV-1) protease, which is obligatory for the production of infectious virions, both belong to the same family of aspartyl proteinases. We have previously shown that the HIV-1 protease inhibitor Indinavir directly inhibits secretion and proteinase activity of Sap in a dose-dependent manner. Furthermore, at very high concentrations, viability of C. albicans is markedly reduced by Indinavir, indicating that HIV-1 protease inhibitors may possess antifungal activity. We thus proposed that these drugs may add to the resolution of mucosal candidiasis in HIV-1 infected subjects. We have now compared three different HIV-1 protease inhibitors. The rank order of Sap inhibition, already significant at 0.1 mg/ml for all protease inhibitors, was Ritonavir > Indinavir > Saquinavir. However, the cross-reactivity of Ritonavir to pepsin was also more pronounced compared with the other two. Indinavir did not affect Candida viability at concentrations up to 1 mg/ml, in line with our previous study. In contrast, at this concentration Saquinavir was even fungicidal as assessed by three different viability assays (colony formation assay, MTT assay, propidium iodide staining) whereas Ritonavir significantly affected the mitochondrial activity only (MTT assay). No influence on Candida viability was observed for any of the three at concentrations of 0.1 mg/ml or lower. It remains to be examined whether HIV-1 protease inhibitors or derivatives thereof may be suitable for in vivo therapy of subjects suffering from mucosal candidiasis resistant to current antimycotics.
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PMID:Dissimilar attenuation of Candida albicans virulence properties by human immunodeficiency virus type 1 protease inhibitors. 1053 86

The use of protease inhibitor (PI) drugs in treatment regimens for HIV-infected patients with hereditary bleeding disorders has been associated with an increased bleeding tendency. To characterize the nature of this bleeding tendency, a retrospective case record analysis was performed on 67 HIV-positive patients with hereditary bleeding disorders who had been treated with PI therapy. 34 patients (51%) developed an increased bleeding tendency on PI therapy, usually within the first few weeks of treatment. As well as an increase in usual joint bleeds, patients developed spontaneous atypical small joint, soft tissue and muscle bleeds. Haematuria was also common. Bleeding episodes tended to respond suboptimally to factor concentrate replacement. Ritonavir was most likely to be associated with bleeding. Nine patients switched first-line PI therapy as a direct consequence of bleeding and seven had no further bleeding problem on their second PI. Factor concentrate usage was significantly increased during the first 6 months of PI therapy compared to the 6 months preceeding treatment. PI therapy is frequently associated with increased bleeding in patients with hereditary bleeding disorders. The mechanism of the bleeding tendency remains to be elucidated.
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PMID:Increased bleeding associated with protease inhibitor therapy in HIV-positive patients with bleeding disorders. 1058 57

HIV protease inhibitors, as components of combination antiretroviral drug regimens, have substantially reduced the morbidity and mortality associated with HIV infection. They selectively block the action of the virus-encoded protease and stop the virus from replicating. In general, these drugs have poor systemic bioavailability and must be dosed with respect to meals for optimal absorption. Protease inhibitor-containing regimens require ingestion of a large number of capsules, are costly, and produce or are susceptible to metabolic drug interactions. Simultaneous administration of two protease inhibitors takes advantage of beneficial pharmacokinetic interactions and may circumvent many of the drugs' undesirable pharmacologic properties. For example, ritonavir increases saquinavir concentrations at steady state by up to 30-fold, allowing reduction of saquinavir dose and dosing frequency. Ritonavir decreases the systemic clearance of indinavir and overcomes the deleterious effect of food on indinavir bioavailability. These benefits reflect inhibition of presystemic clearance and first-pass metabolism, as well as inhibition of systemic clearance mediated by hepatic cytochrome P450 3A4. Several dual protease inhibitor combination regimens have shown great promise in clinical trials and are now recommended as components of salvage therapy for HIV-infected patients.
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PMID:Dual protease inhibitor therapy in HIV-infected patients: pharmacologic rationale and clinical benefits. 1083 50

(1) Recent consensus recommendations agree that first-line treatment of HIV infection should consist of a three-drug regimen combining a protease inhibitor and two nucleoside reverse transcriptase inhibitors. Some recommendations specifically advise against using the current formulation of saquinavir, but none express a preference for one of the other three protease inhibitors currently marketed in France (indinavir, nelfinavir and ritonavir). (2) These HIV protease inhibitors have established efficacy on viral load and the CD4+ lymphocyte count. Saquinavir may have lower virological efficacy. (3) The clinical efficacy of three-drug regimens containing indinavir or saquinavir is well demonstrated in patients at an advanced stage of HIV disease. (4) The risk of viral resistance is not currently a factor in choosing a HIV protease inhibitors. (5) Several epidemiological studies have compared the risk of adverse effects on three-drug regimens including indinavir, ritonavir or saquinavir. In these studies saquinavir was the best-tolerated drug and ritonavir the worst-tolerated. (6) Ritonavir interacts with many drugs. The poor bioavailability of the current saquinavir formulation also leads to risk of interactions. (7) Treatment constraints differ from one protease inhibitor to another, and these must be taken into account case by case. (8) The daily cost of treatment is not currently an important factor in choosing among the various preparations. (9) Taking into account efficacy, adverse effects, interactions and treatment constraints, the combination of indinavir with two nucleoside reverse transcriptase inhibitors currently seems to be the best choice for the largest number of patients. (10) If problems of compliance arise, nelfinavir can be an alternative to indinavir. (11) In patients at an advanced stage of HIV disease who comply well with their treatment, saquinavir can also be an alternative to indinavir.
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PMID:The choice of HIV protease inhibitor: indinavir is currently the best option. 1084 67

Ritonavir (RTV), a protease inhibitor, and carbamazepine (CBZ), an anticonvulsant, were administered concurrently to a patient who had human immunodeficiency virus infection and epilepsy. The combination resulted in elevated serum concentrations of CBZ, with accompanying vomiting, vertigo, and transient liver dysfunction. After discontinuing RTV and reducing the dosage of CBZ, the serum concentration of CBZ returned to the optimal range, symptoms subsided, and liver function returned to baseline. Carbamazepine is metabolized in the liver to a large extent by the cytochrome P450 (CYP) system, especially CYP3A4, 2C8, and 1A2, whereas RTV is metabolized primarily by CYP3A and is a potent inhibitor of this enzyme. Careful clinical monitoring may help prevent adverse drug interactions when these drugs are administered concurrently.
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PMID:Potential interaction between ritonavir and carbamazepine. 1090 77

The relationship between ritonavir plasma concentration, efficacy, and tolerance was evaluated in 31 children with advanced HIV infection who were receiving a triple therapy with ritonavir as protease inhibitor. Median CD4+ lymphocyte count and median viral load before the initiation of ritonavir-containing combination therapy were 1320 cells/mL and 5 log10 copies/mL, respectively. Ritonavir was given at a dose ranging from 300 to 450 mg/m2 twice daily. The median follow-up of triple therapy was 19 months. Response was defined as a drop of viremia of more than 1 log. Plasma drug levels were determined twice during the observation period: after at least 4 weeks and after 3 months of combined treatment. Samples were collected before (residual) and 2 hours (T2) after drug intake. Cholesterol, triglycerides, alanine transaminase, aspartate transaminase, and gamma-glutamyl transpeptidase were assessed at the same time. The median values of ritonavir residual and T2 levels were 1.64 mg/L and 5.9 mg/L at observation 1 and 3.35 mg/L and 6.29 mg/L at observation 2, respectively. According to virologic response, median residual concentrations of ritonavir were 3.17, 2.52, and 1.04 mg/L for the complete, the partial, and the no-response groups. The authors observed a wide intersubject variability of ritonavir concentrations with an increase in residual levels between the two observation periods. Residual levels were correlated with virologic response whereas there was no direct association between T2 levels and long-term response. Patients with complete or partial response displayed statistically significantly higher residual concentrations than the no-response group. No correlation could be demonstrated between elevated plasma drug concentrations and abnormal cholesterol or triglycerides values. These results emphasize the importance of a sustained high ritonavir concentration to achieve optimal treatment efficacy. Furthermore, these results prove the clinical benefit of therapeutic drug monitoring and could potentially improve patient evaluation in terms of treatment efficacy, compliance, and viral resistance.
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PMID:Relationship between efficacy, tolerance, and plasma drug concentration of ritonavir in children with advanced HIV infection. 1094 79

Shortly after the introduction of protease inhibitor drugs (PIs) for the treatment of human immunodeficiency virus infection an association between these drugs and an increased bleeding tendency in patients with hereditary bleeding disorders was observed. Not only do patients experience an increased bleed frequency in usual sites, but bleeds can also occur in unusual places such as the finger joints. Mucus membrane bleeding and haematuria are also common. Ritonavir appears to be associated with the highest risk of bleeding followed by indinavir. As yet there has not been enough experience with the newer PIs to assess fully their potential to induce increased bleeding, although nelfinavir seems to pose less of a risk than the original PIs. PI-associated bleeds tend to be more resistant to factor concentrate treatment and periods of prophylaxis may be required in individuals with frequent persistent bleeds. Patients continuing on PI therapy tend to develop a tolerance to this adverse effect with time. The mechanism of the bleeding tendency has not been elucidated. There is no consistent evidence of a disturbance of coagulation, fibrinolysis or platelet function which raises the possibility that PIs may exert a direct local effect on blood vessels. It is very important that this class-specific side-effect is recognized and understood by both treaters and patients.
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PMID:Protease inhibitor therapy and bleeding. 1101 90

Neurologic manifestations of HIV infection are quite diverse and can develop into seizures. Because new drug therapies have been developed, it is important to know the interactions between antiretroviral and antiepileptic agents. A 36-year-old patient with HIV developed a set of progressive left hemiparesis and secondarily generalized partial seizures related to progressive multifocal leukoencephalopathy. Phenytoin and carbamazepine were necessary to control the seizures. Instead of diverse antiretroviral therapies, the viral load was increased. Protease inhibitors (ritonavir and saquinavir) were added to the treatment and the patient developed progressive ataxia related to carbamazepine toxicity. Carbamazepine was discontinued and the patient remained asymptomatic. The patient was diagnosed with carbamazepine toxicity related to the introduction of ritonavir. Ritonavir is a potent inhibitor of hepatic cytochrome P450, mainly the CYP3A4 isoform. Carbamazepine is metabolized by this subsystem. Ritonavir acted as a CYP3A4 inhibitor, diminishing carbamazepine metabolism and provoking an increase in serum levels and clinical toxicity. We present a case of interaction between ritonavir and carbamazepine. Interaction between antiepileptic and antiretroviral agents is an emergent problem caused by the increasing association of the two therapies. We recommend strict monitoring of serum antiepileptic drug (AED) levels to avoid toxicity and inadequate seizure control.
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PMID:Protease inhibitor-induced carbamazepine toxicity. 1102 Jan 27

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