Effect of antimalarials on clinical outcomes in lupus nephritis

OBJECTIVES

To evaluate the effect of antimalarial drugs in response to therapy, incidence of LN flares, and progression of kidney disease in a large LN cohort.

METHODS

We retrospectively studied 424 biopsy-proven LN patients followed for >3 years. We obtained demographic, clinical, laboratory, histopathological and treatment variables. Antimalarial use was approached as (i) users vs no users, (ii) according to prevalent vs incident use regarding the LN flare and (iii) according to the type of antimalarial. All outcomes were evaluated by time-to-event analyses. Adjusted hazard ratios were obtained by Cox regression.

RESULTS

The cohort included 424 patients, median age of 29 years (IQR 23-37), 96% female, with a median eGFR of 81 ml/min/1.73 m2 (IQR 48-118) and proteinuria of 3.4 g/g (IQR 1.9-5.5). Antimalarial use was associated with higher complete response (aHR 1.57, 1.08-2.27), lower incidence of kidney flares (aHR 0.63, 0.43-0.92) and lower progression to kidney failure (aHR 0.37, 0.23-0.53). The effect of antimalarials on these outcomes was modified by the presentation eGFR, histological class and/or concomitant initial immunosuppressor. These protective effects were observed in patients with prevalent or incident use regarding the LN flare and patients using hydroxychloroquine. The incidence of toxic retinopathy was 1.7%, 5.7% and 8.8% by 3, 5 and 7 years of continued antimalarial use, respectively.

CONCLUSION

The use of antimalarial drugs is associated with increased response to therapy, lower incidence of kidney flares, and lower progression to kidney failure in LN patients. Conversely, this population is at high risk of toxic maculopathy, and yearly ophthalmologic examination is recommended.

Lupus nephritis: management challenges during pregnancy

Lupus nephritis (LN), a severe complication of systemic lupus erythematosus (SLE), leads to significant kidney inflammation and damage and drastically increases mortality risk. Predominantly impacting women in their reproductive years, LN poses specific risks during pregnancy, including pre-eclampsia, growth restrictions, stillbirth, and preterm delivery, exacerbated by lupus activity, specific antibodies, and pre-existing conditions like hypertension. Effective management of LN during pregnancy is crucial and involves carefully balancing disease control with the safety of the fetus. This includes pre-conception counseling and a multidisciplinary approach among specialists to navigate the complexities LN patients face during pregnancy, such as distinguishing LN flare-ups from pregnancy-induced conditions. This review focuses on exploring the complex dynamics between pregnancy and LN, emphasizing the management difficulties and the heightened risks pregnant women with LN encounter.

Subtherapeutic hydroxychloroquine concentration is associated with increased disease activity and greater organ damage in lupus

OBJECTIVE

To investigate the effects of the serum HCQ concentration on clinical manifestations, disease activity and organ damage in a longitudinal cohort of SLE patients.

METHODS

The 338 SLE patients were assessed with respect to their demographic data, clinical and laboratory findings, Physician's Global Assessment (PGA), adjusted mean SLEDAI-2000 (AMS) and SLICC Damage Index (SDI) annually for 5 consecutive years. Patients were divided into two groups according to their serum HCQ concentration at baseline: subtherapeutic (<500 ng/ml) and therapeutic (≥500 ng/ml) groups. The impact of the HCQ concentration on the clinical outcomes was evaluated in a longitudinal analysis using a generalized estimating equation (GEE).

RESULTS

Of the 338 patients, 287 (84.9%) were in the subtherapeutic group at baseline. This group had a higher incidence of newly developed LN (P = 0.036) and had been prescribed higher mean and cumulative doses of prednisolone (P = 0.003 and P = 0.013, respectively) than the therapeutic group. In multivariable analyses based on GEE, the subtherapeutic group had a higher AMS score (β = 1.398, 95% CI 0.607, 2.189; P < 0.001), higher PGA score (β = 0.328, 95% CI 0.215, 0.441; P < 0.001) and higher SDI score (β = 0.366, 95% CI 0.061, 0.671; P = 0.019) across all 5 years.

CONCLUSION

The subtherapeutic HCQ concentration was associated with the development of new-onset LN, and had significant associations with disease activity and cumulative organ damage in SLE patients over time.

Hydroxychloroquine in nephrology: current status and future directions

Hydroxychloroquine is one of the oldest disease-modifying anti-rheumatic drugs in clinical use. The drug interferes with lysosomal activity and antigen presentation, inhibits autophagy, and decreases transcription of pro-inflammatory cytokines. Owing to its immunomodulatory, anti-inflammatory, anti-thrombotic effect, hydroxychloroquine has been an integral part of therapy for systemic lupus erythematosus and lupus nephritis for several decades. The therapeutic versatility of hydroxychloroquine has led to repurposing it for other clinical conditions, with recent studies showing reduction in proteinuria in IgA nephropathy. Research is also underway to investigate the efficacy of hydroxychloroquine in primary membranous nephropathy, Alport's syndrome, systemic vasculitis, anti-GBM disease, acute kidney injury and for cardiovascular risk reduction in chronic kidney disease. Hydroxychloroquine is well-tolerated, inexpensive, and widely available and therefore, should its indications expand in the future, it would certainly be welcomed. However, clinicians should be aware of the risk of irreversible and progressive retinal toxicity and rarely, cardiomyopathy. Monitoring hydroxychloroquine levels in blood appears to be a promising tool to evaluate compliance, individualize the dose and reduce the risk of retinal toxicity, although this is not yet standard clinical practice. In this review, we discuss the existing knowledge regarding the mechanism of action of hydroxychloroquine, its utility in lupus nephritis and other kidney diseases, the main adverse effects and the evidence gaps that need to be addressed in future research. Created with Biorender.com. HCQ, hydroxychloroquine; GBM, glomerular basement membrane; mDC, myeloid dendritic cell; MHC, major histocompatibility complex; TLR, toll-like receptor.

Diagnosis and treatment of lupus nephritis: a summary of the Consensus Document of the Spanish Group for the Study of Glomerular Diseases (GLOSEN)

Lupus nephritis (LN) is the most frequent serious manifestation of patients with systemic lupus erythematosus (SLE). Up to 60% of SLE patients develop LN, which has a significant impact on their quality of life and prognosis. Recent advances have improved the diagnostic approach to LN, and new drugs that block specific pathways and kidney damage progression have been developed. Several randomized and well-powered clinical trials have confirmed the efficacy of these agents in terms of proteinuria remission and preservation of kidney function in the medium and long term, with an acceptable safety profile and good tolerance. The combination of different therapies allows for reduction of the dose and duration of corticosteroids and other potentially toxic therapies and leads to an increase in the number of patients achieving complete remission of the disease. This consensus document carried out by the Spanish Group for the Study of Glomerular Diseases (GLOSEN) provides practical and updated recommendations, based on the best available evidence and clinical expertise of participating nephrologists.

Hydroxychloroquine in children with proliferative lupus nephritis: a randomized clinical trial

Hydroxychloroquine (HCQ) is an antimalarial agent used to treat mucocutaneous, musculoskeletal, constitutional manifestations of systemic lupus erythematosus (SLE). This study assessed the efficacy and side effects of HCQ in children with proliferative lupus nephritis (LN). This double-blind, randomized, placebo-controlled trial study was conducted on 60 children with proliferative LN classes III and IV treated with steroids and a mycophenolate (MMF) regimen. Patients were categorized into two groups, the HCQ group (n = 30) and the placebo group (n = 30). They were evaluated initially at 6- and a 12-month follow-up by mucocutaneous, ophthalmological examination, and investigations (BUN, creatinine, 24 h proteinuria, triglycerides (TG), cholesterol, Antids-DNA, C3, C4). Disease activity was assessed using the SLE disease activity index (SLEDAI-2 k). After 12 months, TG, cholesterol, 24 h proteinuria, Antids-DNA, and SLEDAI score were significantly decreased in the HCQ group (P: 0.002, 0.012, 0.031, 0.001, respectively). After 12 months, the cumulative probabilities of developing primary end-points (LN partial and complete remission) were 40% and 60% in the HCQ group versus 53.3% and 36.7% in the placebo group (P: 0.002). After 12 months, the HCQ group experienced mucocutaneous alopecia (3.3%), hyperpigmentation (10%), and ophthalmological mild retinal changes (6.7%), but they did not differ significantly from the placebo group.  Cunclusion: HCQ improved the disease and LN activity in children with proliferative LN, with documented skin hyperpigmentation and mild retinal changes following HCQ use in a few cases. This study was registered on http://www.

CLINICALTRIALS

gov/ with trial registration number (TRN): NCT03687905, September 2018 "retrospectively registered."

WHAT IS KNOWN

• Hydroxychloroquine (HCQ) is documented as an adjunctive treatment in children with systemic lupus erythematosus (c-SLE) LN with efficacy in improving lupus musculoskeletal and mucocutaneous manifestations. • Due to the paucity of studies, its effects and side effects in children with LN remain unclear.

WHAT IS NEW

• This pilot randomized clinical trial assessed the efficacy and adverse effects of HCQ in children with proliferative LN. • HCQ had numerous advantages for LN, including rapid and sustained remission, antilipidemic effect, and rapid improvement of kidney functions.

Consensus document of the Spanish Group for the Study of the Glomerular Diseases (GLOSEN) for the diagnosis and treatment of lupus nephritis

A significant number of patients with systemic lupus erythematosus (between 20% and 60% according to different reported series) develop lupus nephritis in the course of its evolution, which directly influences their quality of life and vital prognosis. In recent years, the greater knowledge about the pathogenesis of systemic lupus and lupus nephritis has allowed relevant advances in the diagnostic approach and treatment of these patients, achieving the development of drugs specifically aimed at blocking key pathogenic pathways of the disease. Encouragingly, these immunomodulatory agents have shown in well-powered, randomized clinical trials good clinical efficacy in the medium-term, defined as proteinuria remission and preservation of kidney function, with an acceptable safety profile and good patient tolerability. All this has made it possible to reduce the use of corticosteroids and other potentially more toxic therapies, as well as to increase the use of combined therapies. The present consensus document carried out by the Glomerular Diseases Working Group of the Spanish Society of Nephrology (GLOSEN), collects in a practical and summarized, but rigorous way, the best currently available evidence about the diagnosis, treatment, and follow-up of lupus nephritis patients, including cases of special situations, with the main objective of providing updated information and well-founded clinical recommendations to treating physicians, to improve the diagnostic and therapeutic approach to our patients.

Hydroxychloroquine in systemic lupus erythematosus: overview of current knowledge

The antimalarial hydroxychloroquine (HCQ) has demonstrated several crucial properties for the treatment of systemic lupus erythematosus (SLE). Herein, we reviewed the main HCQ pharmacologic features, detailed its mechanism of action, and summarized the existing guidelines and recommendations for HCQ use in rheumatology with a systematic literature search for the randomized controlled trials focused on lupus. HCQ has been shown to decrease SLE activity, especially in mild and moderate disease, to prevent disease flare and to lower the long-term glucocorticoid need. The numerous benefits of HCQ are extended to pregnancy and breastfeeding period. Based on cohort studies, antithrombotic and metabolic HCQ’s effects were shown, including lipid-lowering properties, which might contribute to an improved cardiovascular risk. Moreover, early HCQ use in antinuclear antibodies positive individuals might delay the progression to SLE. Finally, HCQ has a significant favorable impact on long-term outcomes such as damage accrual and mortality in SLE. Based on these multiple benefits, HCQ is now the mainstay long-term treatment in SLE, recommended by current guidelines in all patients unless contraindications or side effects. The daily dose associated with the best compromise between efficacy and safety is matter of debate. The concern regarding retinal toxicity rather than proper efficacy data is the one that dictated the daily dosage of ⩽5 mg/kg/day actual body weight currently agreed upon.

Hydroxychloroquine administration exacerbates acute kidney injury complicated by lupus nephritis

Background

Hydroxychloroquine (HCQ) has been recommended as a basic treatment for lupus nephritis (LN) during this decade based on its ability to improve LN-related renal immune-mediated inflammatory lesions. As a classical lysosomal inhibitor, HCQ may inhibit lysosomal degradation and disrupt protective autophagy in proximal tubular epithelial cells (PTECs). Therefore, the final renal effects of HCQ on LN need to be clarified.

Method

HCQ was administered on spontaneous female MRL/lpr LN mice with severe proteinuria daily for 4 weeks. Moreover, the MRL/lpr mice with proteinuric LN were subjected to cisplatin-induced or unilateral ischemia/reperfusion (I/R)-induced acute kidney injury (AKI) after 2 weeks of HCQ preadministration.

Results

As expected, HCQ treatment increased the survival ratio and downregulated the levels of serum creatinine in the mice with LN, ameliorated renal lesions, and inhibited renal interstitial inflammation. Unexpectedly, HCQ preadministration significantly increased susceptibility to and delayed the recovery of AKI complicated by LN, as demonstrated by an increase in PTEC apoptosis and expression of the tubular injury marker KIM-1 as well as the retardation of PTEC replenishment. HCQ preadministration suppressed the proliferation of PTECs by arresting cells in G1/S phase and upregulated the expression of cell cycle inhibitors. Furthermore, HCQ preadministration disrupted the PTEC autophagy-lysosomal pathway and accelerated PTEC senescence.

Conclusion

HCQ treatment may increase susceptibility and delay the recovery of AKI complicated by LN despite its ability to improve LN-related renal immune-mediated inflammatory lesions. The probable mechanism involves accelerated apoptosis and inhibited proliferation of PTECs via autophagy-lysosomal pathway disruption and senescence promotion.

Effects of hydroxychloroquine on proteinuria in membranous nephropathy

BACKGROUND

Many patients with primary membranous nephropathy have severe proteinuria unresponsive to optimized renin-angiotensin-aldosterone system inhibitors (RAASi). We evaluated the efficacy and safety of hydroxychloroquine as an adjunctive agent in membranous nephropathy (MN) treatments.

METHODS

We prospectively recruited 126 patients with biopsy-proven primary membranous nephropathy and urinary protein 1-8 g/day while receiving optimized RAASi treatment for ≥ 3 months and well-controlled blood pressure. Forty-three patients received hydroxychloroquine and RAASi (hydroxychloroquine-RAASi group), and 83 patients received RAASi alone (RAASi group). Treatment responses, including proteinuria reduction, complete and partial remission rates, and autoantibody against phospholipase A2 receptor (anti-PLA2R) levels, were compared between the two groups at 6 months and over the long term.

RESULTS

At 6 months, the effective response rate (proteinuria reduction > 30%) (57.5% vs. 28.9%, P = 0.002), clinical remission rate (35.0% vs. 15.7%, P = 0.015), and percentage change in proteinuria (- 51.7% vs. - 21.9%, P < 0.001) were higher, and the rate of switching to immunosuppressants (25.0% vs. 45.8%, P = 0.027) was lower in the hydroxychloroquine-RAASi group than in the RAASi group. Hydroxychloroquine administration was an independent protective factor with an effective response (OR 0.37, P = 0.021). In the long term, the clinical remission rate was higher in the HCQ-RAASi group (62.5% vs. 38.6%, P = 0.013). Hydroxychloroquine therapy was associated with a higher rate of anti-PLA2R reduction (< 20 U/ml) (HR 0.28, P = 0.031). We observed no serious adverse events associated with hydroxychloroquine.

CONCLUSIONS

Hydroxychloroquine could be an option for patients with membranous nephropathy seeking to achieve proteinuria reduction and anti-PLA2R antibody reduction in addition to optimized RAASi. Randomized controlled trials are needed to confirm these findings.

TRIAL REGISTRATION

ChiCTR2100045947, 20210430, retrospectively registered.

The predictive value of serum level of cystatin C for COVID-19 severity

To investigate the potential prognostic value of Serum cystatin C (sCys C) in patients with COVID-19 and determine the association of sCys C with severe COVID-19 illness. We performed a retrospective review of medical records of 162 (61.7 ± 13.5 years) patients with COVID-19. We assessed the predictive accuracy of sCys C for COVID-19 severity by the receiver operating characteristic (ROC) curve analysis. The participants were divided into two groups based on the sCys C cut-off value. We evaluated the association between high sCys C level and the development of severe COVID-19 disease, using a COX proportional hazards regression model. The area under the ROC curve was 0.708 (95% CI 0.594-0.822), the cut-off value was 1.245 (mg/L), and the sensitivity and specificity was 79.1% and 60.7%, respectively. A multivariable Cox analysis showed that a higher level of sCys C (adjusted HR 2.78 95% CI 1.25-6.18, p = 0.012) was significantly associated with an increased risk of developing a severe COVID-19 illness. Patients with a higher sCys C level have an increased risk of severe COVID-19 disease. Our findings suggest that early assessing sCys C could help to identify potential severe COVID-19 patients.

Does hydroxychloroquine improve patient reported outcomes in patients with lupus?

BACKGROUND

Hydroxychloroquine (HCQ) use is associated with less disease activity, flares, damage and improved survival in Systemic Lupus Erythematosus (SLE). However, its effect on patient reported health outcomes (PROs) such as quality of life (QOL) is not known.

METHODS

International data from Study on Outcomes of Lupus (SOUL) from 2,161 SLE patients were compared by HCQ use. Disease activity and damage were assessed using SELENA-SLEDAI and SLICC-ACR/SDI. QOL was evaluated using LupusPRO and Lupus Impact Tracker (LIT). Linear regression analyses were performed with LupusPRO summary scores health related HRQOL, non-health related NHRQOL and LIT as dependent and HCQ use as independent variable. Analyses were undertaken to test mediation of effects of HCQ use on QOL through disease activity.

RESULTS

Mean age was 40.5 ± 12.8 years, 93% were women. Sixty-three (1363/2161) percent were on HCQ. On univariate analysis, HCQ use was associated with (a) better QOL (LupusPRO-HRQOL: β 6.19, 95% CI 4.15, 8.24, P ≤ 0.001, LupusPRO NHRQOL: β 5.83, 95% CI 4.02, 7.64, P ≤ 0.001) and less impact on daily life (LIT: β -9.37, 95% CI -12.24, -6.50, P ≤ 0.001). On multivariate and mediational analyses, the effects of HCQ on QOL were indirectly and completely mediated through disease activity.

CONCLUSIONS

HCQ use in SLE is associated with better patient reported health outcomes (LupusPRO-HRQOL and NHRQOL and impact on daily life), and the effects are mediated through disease activity. This information can facilitate patients and physician's communication with decision-making regarding the use of HCQ for SLE management.

Eurolupus cyclophosphamide plus repeated pulses of methyl-prednisolone for the induction therapy of class III, IV and V lupus nephritis

OBJECTIVE

To study whether adding repeated 125 mg methyl-prednisolone pulses (MP) to Eurolupus fortnightly intravenous cyclophosphamide (CYC) improves remission of lupus nephritis (LN) compared with recommended schedules.

METHODS

Observational comparative study of patients with biopsy-confirmed class III, IV or V LN: 30 in the mycophenolate (MMF) group, 25 in the CYC group and 38 in the CYC-MP group. The main efficacy outcome was complete response at 12 months.

RESULTS

Patients in the CYC-MP group received lower doses of prednisone within 6 months (mean 8.5 mg/d, vs. 15 mg/d in the MMF group vs. 24 mg/d in the CYC group, respectively). The complete response rates at 12 months were: CYC-MP 86%; CYC 56%; MMF 47% (p = 0.002) at Pr/Cr <0.5; CYC-MP 86%; CYC 65%; MMF 63% (p = 0.07) at Pr/Cr ≤0.7. The cumulative 12-month response rates for the CYC-MP, CYC and MMF groups were, respectively, 0.90, 0.58 and 0.63 (p = 0.004). In the adjusted Cox model, patients receiving CYC-MP were more likely to achieve complete response at Pr/Cr <0.5 than those in the MMF (HR vs. CYC-MP 0.33, 95%CI 0.16-0.65) and the CYC groups (HR vs. CYC-MP 0.47, 95%CI 0.21-1.04). Glucocorticoid-related toxicity was seen in 2.6% of the CYC-MP group, 24% of the CYC group and 20% of the MMF group (p = 0.029).

CONCLUSION

The addition MP of 125 mg to each fortnightly dose of 500 mg of CYC improves response rates and reduces the need for oral glucocorticoids in patients with class III, IV and V LN.

Association of antimalarial drugs with decreased overall and cause specific mortality in systemic lupus erythematosus

OBJECTIVE

To evaluate the association and dose-response pattern between antimalarial drugs and overall and cause specific mortality in SLE patients.

METHODS

Medical records including information on HCQ/chloroquine (CQ) prescription were extracted from Jiangsu Lupus database. The database was designed to collect data from SLE patients that first-hospitalized during 1999-2009 in Jiangsu province, China, and a follow-up for survival status was performed in 2010 and 2015. Cox and restricted cubic spline models were used to estimate the hazard ratio and 95% CI.

RESULTS

We identified 221 deaths among 2446 SLE patients in total. Compared with non-users, decreased overall mortality was associated with either HCQ or CQ users, with adjusted hazard ratio (95% CI) of 0.49 (0.35, 0.67) and 0.49 (0.27, 0.87), respectively. The association between HCQ/CQ and overall mortality was similar across subgroups, such as patients with comorbidities and organ involvements. Interestingly, both the time and the daily dosage of HCQ/CQ use were related to decreased mortality of SLE in a linear dose-response relationship. In cause specific analyses, HCQ/CQ was inversely associated with death from renal insufficiency and other organ (cardiopulmonary, gastrointestinal and haematological) involvements, with adjusted hazard ratio (95% CI) of 0.23 (0.09, 0.55) and 0.25 (0.10, 0.62), respectively, yet it was not significantly associated with mortality from infection and neuropsychiatric involvements.

CONCLUSION

Antimalarial drugs were associated with lower risk of SLE mortality, especially renal insufficiency- and other organ involvement-related death. The protective effects for survival might be augmented by adherence and full dosage of these drugs.

Kidney outcomes for children with lupus nephritis

Systemic lupus erythematosus is a rare lifelong multi-systemic autoimmune condition. Juvenile-onset SLE (JSLE) is recognized to have a more active disease course when compared with adult-onset disease and patients have a worse long-term survival. Kidney involvement occurs in over 50% of children and treatment decisions are guided by the histological classification. Several international groups have produced treatment protocols that rely on an intense period of immunosuppression to halt the acute kidney inflammatory process, followed by maintenance therapy with close observation for disease improvement and prompt evaluation of disease flares. A reduced glomerular filtration rate at presentation is predictive of later stage chronic kidney disease (CKD) in multivariate analysis. Kidney remission remains suboptimal with only 40-60% of patients achieving complete remission. Kidney flares are seen in over a third of patients. The rate of CKD 5 is reported to be up to 15% and the presence of lupus nephritis (LN) has an established link with an associated increase in mortality. In established kidney failure, transplantation seems to be the optimal kidney replacement modality for this group of patients, ideally after a period of disease quiescence. Modified outcome measures in clinical trials have demonstrated that biologic agents can be effective in this disease. Current biologic agents under investigation include obinutuzimab, belimumab, atacicept, anifrolumab, tocilizumab, eculizumab, dapirolizumab, and abatacept. Future research should focus on discovering early disease biomarkers, including surrogates for later cardiovascular disease, and evaluating biological agents as adjuncts to improve the rates of complete remission and subsequently influence the kidney outcome. The aim of this review article is to summarize the current kidney outcomes for this disease with a view to identifying key areas that may help to reduce the risk of long-term CKD.

Update on antimalarials and systemic lupus erythematosus

PURPOSE OF REVIEW

The purpose of this review is highlighting the most recent evidence on the clinical efficacy and toxicity of antimalarials in systemic lupus erythematosus (SLE).

RECENT FINDINGS

New data confirm the effects of antimalarials in preventing SLE activity, damage and infections and in decreasing mortality. An important reduction in use of health resources is related to continued antimalarial use. Hydroxychloroquine (HCQ) may prevent preeclampsia in pregnant women with SLE. HCQ ocular toxicity is infrequent and could be associated with blood levels. Gastrointestinal and skin toxicity are underrecognized and could influence adherence. Prolongation of QT interval is extremely unusual with HCQ. Doses of HCQ of 200 mg/day seem to offer a good efficacy/toxicity balance. HCQ protection against herpes zoster and Pneumocystis jirovecii infection has been shown. On the contrary, HCQ prescription by doctors and adherence by patients are both under recommended standards. The recent coronavirus disease 2019 pandemic has resulted in a significant shortage of HCQ in many countries with possible consequences in the correct treatment of lupus patients.

SUMMARY

Recent evidence reinforces the central role of HCQ in SLE therapy. The reduction in activity, damage accrual and mortality is consistent across studies, countries and ethnical groups. On the contrary, and despite the well established beneficial effects of prolonged regular HCQ therapy, many SLE patients do never take this drug or it is eventually stopped in the setting of severe flares, pregnancy or presumed toxicity. Every effort must be made to assure the correct prescription of HCQ and not to withdraw the drug unless unequivocal signs of toxicity are present.