Stavudine once daily

Antiretroviral drug use and the risk of falls in people living with HIV: a systematic review and meta-analysis

Objective

The risk of falls in people living with HIV (PLHIVs) on antiretroviral therapy (ART) has received little attention in the literature. The aim of the meta-analysis is to quantify the association between fall risk and various categories of drugs used in ART.

Material and Methods

PubMed, Google Scholar, Embase, and the Cochrane Central Register of Controlled Trials were systematically searched from inception to January 2023. Any observational study or controlled trial that reported on the relationship of at least one antiretroviral drug with falls in PLHIVs was included. Data on the frequency of single fallers, multiple fallers (≥2 falls), and non-fallers were extracted and studied for each drug and drug category. The pooled results were reported as an odds ratio (OR) with a 95% confidence interval (CI).

Results

A total of five observational studies (51 675 participants) were included out of 414 articles obtained through a literature review. Stavudine use was found to be associated with an increased risk of single falls in PLHIVs (OR: 1.69, 95% CI: 1.08-2.66, P=0.02). However, efavirenz (OR: 0.82, 95% CI=0.76-0.89, P<0.001) and zidovudine (OR: 0.82, 95% CI=0.77-0.92, P<0.001) were found protective against the single falls. Didanosine had no significant association with fall risk (OR: 1.23, 95% CI: 0.78-1.93, P=0.37). Likewise, protease inhibitors, integrase inhibitors, nucleoside reverse transcriptase inhibitors, and non-nucleoside reverse transcriptase inhibitors were discovered to have no significant association with fall risk.

Conclusion

Most drug categories of ART have no significant association with the risk of falls in PLHIVs. However, certain drugs, such as didanosine and stavudine, which have the inherent effect of causing balance deficits and neuropathy, should be used cautiously.

Synthesis of enantiomerically pure D- and L-bicyclo[3.1.0]hexenyl carbanucleosides and their antiviral evaluation

Based upon the fact that l-nucleosides have been generally known to be less cytotoxic than d-counterparts, l-bicyclo[3.1.0]hexenyl carbanucleoside derivatives with a fixed north conformation were designed and synthesized by employing a novel synthetic strategy starting from (R)-epichlorohydrin in order to search for new anti-HIV agents with high potency and less cytotoxicity. A tandem alkylation, γ-lactonization, a chemoselective reduction of ester in the presence of γ-lactone functional group, a RCM reaction, and a Mitsunobu coupling reaction were used as key reactions. d-Counterpart nucleosides were also prepared according to the same synthetic method. Among the synthesized carbanucleosides, d-thymine nucleoside, d-2 and l-thymine nucleoside, l-2 exhibited excellent anti-HIV-1 and -2 activities, in MT-4 cells, which were higher than those of ddI, an anti-AIDS drug. Whereas d-2 exhibited high cytotoxicity in MT-4 cell lines, l-2 did not show any discernible cytotoxicity in all cell lines tested, reflecting that l-2 may be a good candidate for an anti-AIDS drug. l-2 also showed weak anti-HSV-2 activity without cytotoxicity. However, none of the synthesized nucleosides exhibited antiviral activities against RNA viruses including coxsakie, influenza, corona and polio viruses, maybe due to their 2′,3′-dideoxy structure. Potent antiviral effects of d-2 and l-2 indicate that nucleosides belonging to a class of D4Ns can be an excellent candidate for anti-DNA virus agents. This research strongly supports l-nucleosides of a class of D4Ns to be a very promising candidate for antiviral agents due to its low cytotoxicity and a good antiviral activity.

Pharmacokinetic properties of nucleoside/nucleotide reverse transcriptase inhibitors

Options for antiretroviral therapy in patients infected with HIV continue to expand as new drugs are integrated into treatment regimens. Nonetheless, nucleoside/nucleotide reverse transcriptase inhibitors (NRTIs/NtRTIs) remain the backbone of highly active antiretroviral therapy (HAART). With the approval of emtricitabine in 2003, there are now 8 Food and Drug Administration (FDA)-approved NRTIs/NtRTIs. Several of these agents are effective as once-daily therapy, including didanosine, lamivudine, extended-release stavudine (FDA approved, but not currently available), tenofovir DF, and emtricitabine. Recent results from pharmacokinetic and clinical trials indicate that another NRTI, abacavir, may also be effective as a once-daily therapy, and FDA approval of once-daily dosing is anticipated. NRTIs are inactive as administered, requiring anabolic phosphorylation within target cells to achieve their antiretroviral effects. All NRTIs are converted to nucleoside triphosphates, which serve as the active metabolites (the NtRTI, tenofovir DF, only requires conversion to the diphosphate form). Frequency of drug administration is closely related to the pharmacokinetic properties of a drug. The key parameter is the half-life; however, the plasma elimination half-life of the NRTIs/NtRTIs as administered is of little use in developing a dosing schedule. Rather, the intracellular half-life of the nucleoside triphosphate is the relevant parameter. This article reviews the pharmacokinetic properties, particularly those of the various phosphorylation steps, of the NRTIs/NtRTIs.

Once-daily antiretroviral therapy: Spanish Consensus Statement

BACKGROUND

Administration of antiretroviral therapy (ART) once daily is creating extraordinary interest among the members of the scientific community and also among those who receive the therapy. However, in clinical practice, some doubts remain about its use.

OBJECTIVES

This document examines the characteristics and possibilities of treatment administered once daily.

METHODS

Consensus of 248 Spanish experts in the field.

RESULTS

Once-daily dosing is considered an added value which could favour adherence and, therefore, efficacy, as well as the quality of life of certain patients, however, the objective of adequate adherence in the long term is often difficult to achieve regardless of the treatment used. In theory, any patient can receive once-daily therapy, although some patients could particularly benefit from it, e.g. those with unfavourable social or personal circumstances, including drug users, patients whose treatment must be supervised, patients receiving multiple medications, or those who need rescue therapy after multiple treatment failures. At present, it is possible to design once-daily ART using some of the combinations of drugs considered as first-choice in national and international recommendations for antiretroviral therapy, but the options are still limited. The marketing of new drugs with this characteristic could allow us to increase the number and types of patient who can benefit from once-daily regimens, including those patients who need rescue therapy.

CONCLUSIONS

Once-daily ART is a good alternative to regimens administered several times each day when a potent combination of active drugs is available.

Actual medication pill burden and dosing frequency in HIV-infected patients with undetectable viral loads

Studies have shown equivalent or improved outcomes with once-daily antiretroviral (ARV) regimens, but have failed to quantify the true daily dosing frequency and pill burden of HIV-infected patients, by not considering concomitant medications. This study was conducted to describe the total daily number (pill burden) and dosing frequency for all oral medicines, and not just ARV medications in HIV-infected patients with undetectable viral loads. A retrospective chart review of patients with undetectable viral loads in an HIV primary care clinic identified dosing frequency and pill burden for all prescribed medications. These patients were divided into those with concomitant medications (WITH) and those only on ARV medications (WITHOUT). One hundred and seventeen patients qualified for the evaluation. Ninety-three were in the WITH group and 24 were in the WITHOUT group. WITH patients were older (p < 0.05), and had advanced US Centers for Disease Control and Prevention (CDC)-defined HIV disease stage (p< 0.05), a longer duration of HIV infection (p= 0.03), and a longer duration of AIDS (p= 0.02). WITH patients had a significantly greater total pill burden (p<0.01) and dosing frequency (p<0.001) when considering all medications. Assessing only ARV medications, a significant difference existed only in pill burden (mean +/- SD) (WITH = 9.91 +/- 2.1 versus WITHOUT = 6.6 +/- 1; p < 0.01), and no difference existed in ARV dosing frequency of 2.09 +/- 1.9 and 1.83 +/- 1.7, respectively (p = 0.07). Higher dosing frequencies and pill burdens were present in patients with co-morbid conditions. All patients were on more than once-daily therapies. Dosing requirements for non-ARV medications should also be considered when optimizing or simplifying ARV regimens.

Synthesis and conformational analysis of a locked analogue of carbovir built on a bicyclo[3.1.0]hex-2-enyl template

The synthesis and biological evaluation of a carbovir analogue (5) built on a bicyclo[3.1.0]hex-2-enyl template is described. A conformational analysis using density functional theory at the B3LYP/6-31G* level has been carried out on the rigid pseudosugar template of 5, the cyclopentene moiety of carbovir and the bicyclo[3.1.0]hex-2-yl pseudosugars of two isomeric carbonucleosides (12 and 13) containing exo- and endo-fused cyclopropane rings. The results show that while the planar configuration of the fused cyclopentane ring of compound 5 helps retain weak anti-HIV activity, the ability of the cyclopentene ring of carbovir to easily adopt a planar or puckered conformation with little energy penalty may prove to be a crucial advantage. The bicyclo[3.1.0]hex-2-yl nucleosides 12 and 13 that were inactive against HIV exhibited stiffer resistance to having a planar, fused cyclopentane moiety.

Stavudine effects on rat pregnancy outcome

OBJECTIVE

Stavudine is an inhibitor of HIV reverse transcriptase and acts as a chain terminator during DNA synthesis. The aim of the study presented here was to evaluate the effects of stavudine during rat pregnancy.

METHODS

Female rats were randomly divided into four treatment groups: GI (treated with the drug vehicle); GII; GIII; and GIV (treated with 1, 3 or 9 mg/kg of stavudine, respectively) (n = 25 pregnant rats for every group). Rats were treated by gavage once daily. The treatment period extended from day 0 until the 20th day of pregnancy. Body weights were recorded weekly during this period. At term, the rats were sacrificed, and the implantation sites and number of fetuses and resorptions were recorded. The fetuses were evaluated for external abnormalities under a stereomicroscope.

RESULTS

No differences in body weight gain between the groups were observed. The mean number of implantations per dam in stavudine-treated groups was higher than in the control group (P < 0.05); however, only GIII presented an increase in the mean number of resorptions compared to the other groups (P < 0.01). The resorption/implantation rate was higher in the GII group and lower in the GIV group as compared to the other groups. Neither the mean fetal weights nor the placental weights differed significantly among the groups. No external anomalies were observed at dissection in rat fetuses, placentae or uteri.

CONCLUSION

Rat pregnancy outcome seems to be affected by stavudine, mainly with respect to the mechanisms of intrauterine concept survival.

1,3-Dihydrobenzo[ c ]furan nucleoside analogues: additional studies of the thymine derivative

The detailed study of the 1,3-dihydrobenzo[c]furan derivative of thymine is reported. The lack of anti-HIV activity of this compound in cell culture experiments is shown to be related to the inability of the corresponding 5'-triphosphate derivative to interact efficiently with the reverse transcriptase.

Stereoselective and Concentration-Dependent Polarized Epithelial Permeability of a Series of Phosphoramidate Triester Prodrugs of d4T: An in Vitro Study in Caco-2 and Madin-Darby Canine Kidney Cell Monolayers

Nucleoside analogs are successful, widely used antiviral and anticancer therapeutics. Nucleotide prodrugs (i.e., pronucleotide) have increasingly been used to improve in vivo efficacy of nucleoside analogs. In this study, we evaluated the permeability of a series of phosphoramidate triester prodrugs of the anti-HIV drug 2',3'-didehydro-2',3'-dideoxythymidine across monolayers of Caco-2, Madin-Darby canine kidney (MDCKII) epithelial cell line, and its recombinant clone containing the human MDR1/P-gp gene (MDR1-MDCKII). Transport was studied in the apical-to-basolateral (A-B) and the basolateral-to-apical directions (B-A). The impact upon transport of differences in stereochemistry at the chiral phosphate center was evaluated. In the Caco-2 and MDCK models the A-B permeability was lower than expected based on the lipophilicity of the compounds, suggesting the involvement of a polarized efflux system and/or metabolic degradation in limiting the absorption of these ester-based prodrugs. Average permeability values through cell monolayers obtained in the A-B direction were lower than in the B-A direction. The inclusion of the P-glycoprotein (P-gp) inhibitor verapamil in the transport medium markedly increased the permeability in the A-B direction, whereas decreasing it in the opposite direction, suggesting an efflux mechanism mainly mediated by P-gp. Stereoselective permeability was significant for the most lipophilic compounds, where the diastereoisomer possessing the slower eluting time on a reverse-phase high-performance liquid chromatography column was transported through Caco-2 and MDCK monolayers at higher rate.