Understanding depot antipsychotics: an illustrated guide to kinetics

Long-Acting Injectable Antipsychotics-A Review on Formulation and In Vitro Dissolution

Long-acting injectable (LAI) neuroleptics constitute an effective therapeutical alternative for individuals suffering from persistent mental illness. These injectable pharmaceuticals help patients manage their condition better and improve long-term outcomes by preventing relapses and improving compliance. This review aims to analyse the current formulation aspects of LAI neuroleptics, with particular emphasis on analysis of drug release profiles as a critical test to guarantee drug quality and relevant therapeutical activity. While there is no officially approved procedure for depot parenteral drug formulations, various dissolution tests which were developed by LAI manufacturers are described. In vitro dissolution tests also possess a critical function in the estimation of the in vivo performance of a drug formulation. For that reason, thorough inspection of the in vitro-in vivo correlation (IVIVC) is also discussed.

Roles of Fatty Acid Chain Length and Enzyme-Oriented Drug Controlled Release from pH-Triggering Self-Assembled Fatty Acid Conjugated Quetiapine Nanosuspensions

Background

Quetiapine (QTP) is a first-line antipsychotic drug, but its therapeutic druggability and patient adherence were limited due to high oral dose strength, low bioavailability and physicochemical/biopharmaceutical issues.

Purpose

To investigate the roles of fatty acid chain length and enzyme-oriented QTP controlled release from pH-triggering self-assembled fatty acid conjugated QTP nanosuspensions (NSPs).

Methods

QTP was conjugated with different chain length fatty acids (C10-decanoic acid, C14-myristic acid, C18-stearic acid) to obtain QTP-fatty acid conjugates (QFCs: QD, QM, QS) by exploiting 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide/4-dimethylaminopyridine (EDC/DMAP) conjugation chemistry. Then, the solubility, partitioning coefficient (log P), cell viability and cleavage kinetics of QFCs were evaluated. The pH-triggering self-assembled behaviors of QFCs to form QTP-fatty acid NSPs (QDN, QMN, QSN) by varying pH, QFC concentration and proton-to-QTP ratios were characterized. The morphological images, critical micelle concentration (CMC), physicochemical properties and enzyme-oriented QTP controlled release of NSPs were examined.

Results

Three QFCs were synthesized with different chain length fatty acids from QTP after desalting fumarate from QTP fumarate. The pH, QFC concentration and proton-to-quetiapine molar ratio could influence physicochemical properties and nanonization behaviors of QFCs. All three QFCs showed no effect on the viability of myoblast cells. The pH-triggering self-assembly of amphiphilic QFCs to form nanoparticles (NPs) occurred as the amine moiety of QTP was readily ionized in a strongly acidic environment (pH 1.2). Interestingly, the longer the fatty acid chain length, the lower water solubility, the higher log P (lipophilicity) and the smaller NP particle size were observed. The conversion rate of QFCs to liberate QTP by esterase in human plasma and liver S9 fractions was also inversely proportional to the fatty acid carbon chain length. Interestingly, the freeze-dried QMN showed the esterase-oriented controlled release of QTP over one month, unlike the initial burst release of QDN or the slowly delayed release pattern of QSN.

Conclusion

A new pH-triggering self-assembled nanonization platform was developed using different chain length fatty acid conjugated QTP in low pH environment. By varying fatty acid chain length, the enzyme-oriented QTP controlled release dosage form was challenged to enhance the therapeutic effectiveness of QTP.

Microneedle array patches for sustained delivery of fluphenazine: A micron scale approach for the management of schizophrenia

Schizophrenia is a severe chronic mental illness characterised by impaired emotional and cognitive functioning. To treat this condition, antipsychotics are available in limited dosage forms, mainly oral and injectable formulations. Although injectable antipsychotics were designed to enhance adherence, they are invasive, painful and require a healthcare professional to be administered. To overcome such administration issues, extensive research has been focused on developing transdermal antipsychotic formulations. In this work, three microneedle (MN) systems were developed to deliver fluphenazine (FLU) systemically. A decanoic prodrug of FLU called fluphenazine decanoate (FLUD) was used in two of the MN formulations due to its high lipophilicity. FLU-D was loaded into dissolving MNs and nanoemulsion (NE)-loaded MNs. The parent drug FLU was loaded into poly(lactic-co-glycolic acid) (PLGA)-tipped MNs. All MN systems were characterised and evaluated in vitro and in vivo. The in vivo evaluation of the three developed MN systems showed their ability to deliver FLU into the systemic circulation, as the Cmax of FLU-D dissolving MNs was 36.11 ± 12.37 ng/ml. However, the Cmax of FLU-D NE loaded dissolving MNs was 12.92 ± 6.3 ng/ml and for FLU-PLGA tipped MNs was 21.57 ± 2.45 ng/ml. Compared to an intramuscular (IM) injection of FLU-D in sesame oil, the relative bioavailabilities were 26.96 %, 21.73 % and 42.45 % for FLU-D dissolving MNs, FLU-D NE dissolving MNs and FLU-PLGA tipped MNs, respectively. FLU plasma levels were maintained above the minimum human therapeutic limits for a week. Consequently, these various MN formulations are considered to be a viable options for the transdermal delivery of fluphenazine and its prodrug. The three MN systems developed offer patients a user-friendly, painless, and convenient long-acting delivery method for FLU. Reducing dosing frequency and using less invasive drug administration methods can enhance adherence and foster positive therapeutic outcomes. This study demonstrates the capability and adaptability of MNs technology to transport hydrophobic molecules from the skin to the systemic circulation.

Switching to long-acting injectable antipsychotics: pharmacological considerations and practical approaches

INTRODUCTION

Long-acting injectable antipsychotics (LAIs) are an effective, but potentially underutilized treatment option in schizophrenia and other severe mental illnesses. Prescribing information typically focuses on how to initiate treatment from the corresponding oral formulations. However, in clinical practice other scenarios, such as switching from other oral antipsychotics or other LAIs, occur frequently, requiring guidance.

AREAS COVERED

Pharmacodynamic properties of antipsychotics and their relation to rebound symptoms. Pharmacokinetic properties of LAIs and their implications for switching approaches. Specific approaches to switching to LAIs.

EXPERT OPINION

The LAI landscape has evolved significantly in the last decade with more formulations available, longer dosing intervals, and extended indications. However, currently available LAIs have various shortcomings, e.g. short dosing intervals, need for oral supplementation, loading regimens, deep intramuscular injection and/or restricted indications. Recent improvements include a one-day initiation option for aripiprazole lauroxil, aripiprazole monohydrate once-monthly, risperidone in situ microparticles and subcutaneous risperidone. Future LAI developments should focus on longer dosing intervals, subcutaneous administration, expansion of LAIs beyond currently available antipsychotic agents and indications beyond schizophrenia and bipolar disorder. In the future, LAIs might become a first-line treatment after initial oral stabilization for chronic mental disorders with need for maintenance treatment and presence of significant non-adherence.

Efficacy of Transcranial Direct-Current Stimulation in Catatonia: A Review and Case Series

Catatonia is a severe neuropsychiatric syndrome, usually treated by benzodiazepines and electroconvulsive therapy. However, therapeutic alternatives are limited, which is particularly critical in situations of treatment resistance or when electroconvulsive therapy is not available. Transcranial direct-current stimulation (tDCS) is a promising non-invasive neuromodulatory technique that has shown efficacy in other psychiatric conditions. We present the largest case series of tDCS use in catatonia, consisting of eight patients in whom tDCS targeting the left dorsolateral prefrontal cortex and temporoparietal junction was employed. We used a General Linear Mixed Model to isolate the effect of tDCS from other confounding factors such as time (spontaneous evolution) or co-prescriptions. The results indicate that tDCS, in addition to symptomatic pharmacotherapies such as lorazepam, seems to effectively reduce catatonic symptoms. These results corroborate a synthesis of five previous case reports of catatonia treated by tDCS in the literature. However, the specific efficacy of tDCS in catatonia remains to be demonstrated in a randomized controlled trial. The development of therapeutic alternatives in catatonia is of paramount importance.

Effect of long acting injectable antipsychotics on course and hospitalizations in bipolar disorder - a naturalistic mirror image study

PURPOSE

To determining whether the addition of a long-acting injectable antipsychotic (LAI-AP) has a positive effect on prognosis in bipolar disorder.

MATERIALS AND METHODS

Medical records of patients with bipolar disorder who were using LAI-AP at least for one year in the community mental health center (CMHC) until March 2020 were investigated. Comparisons were made between the period of one year before and after the initiation of LAI-AP. Hospital admission was the primary outcome. Residual symptom severity and functionality were evaluated with Personal and Social Performance Scale (PSP), Young Mania Rating Scale (YMRS), and Beck Depression Inventory (BDI).

RESULTS

There were 197 patients with bipolar disorder who were attending to the CMHC and 17 of them were under maintenance treatment with LAI-AP for at least one year. The LAI-APs used were aripiprazole (n = 8), paliperidone (n = 5) and risperidone (n = 4). Duration of illness was 13.5 ± 8.02 years and duration of LAI-AP treatment was 24.8 ± 22.74 months (median: 18). During the one-year period after the LAI-AP initiation, there were fewer days spent in hospital (2.5 ± 5.68 vs. 15.5 ± 20.59 days, p = .026) and the number of hospitalizations was lower than the year before the LAI-AP use (0.1 ± 0.39 vs. 0.9 ± 1.24 hospitalizations, p = .013). During the recovery period with LAI antipsychotics, there were mild residual symptoms presented with mean PSP (70.2), YMRS (1.7) and BDI (7.6) scores.

CONCLUSION

LAI-AP use may have positive effect on course for selected patients with a long history of bipolar disorder.

Guidance on the clinical understanding and use of long-acting injectable antipsychotics in Schizophrenia: Hong Kong Consensus Statements

AIMS

There is increasing evidence showing the importance of long-acting injectable antipsychotics in the management of schizophrenia, especially in terms of improving patient medication compliance. A panel of experienced clinicians in Hong Kong mapped out a set of consensus statements with an aim to facilitate the understanding and use of long-acting injectable antipsychotics among local physicians.

METHODS

Eight discussion areas regarding long-acting injectable antipsychotics were selected by the chairman of the consensus group. A series of meetings were held for the panelists to discuss the published literature and their clinical experience, followed by the drafting of consensus statements. At the final meeting, each consensus statement was voted on anonymously by all members based on its practicability of recommendation in Hong Kong.

RESULTS

A total of 12 consensus statements on the rational use of long-acting injectable antipsychotics were established and accepted by the consensus group.

CONCLUSION

The consensus statements aim to provide practical guidance for Hong Kong physicians on the use of long-acting injectable antipsychotics in schizophrenia patients. These statements may also serve as a reference for doctors in other parts of the Asia-Pacific region.

Monitoring and improving antipsychotic adherence in outpatient forensic diversion programs

Outpatient diversion programs present an opportunity for severely mentally ill defendants to receive psychiatric treatment and have alleged offenses dismissed by the court. Moreover, the successful completion of pretrial diversion is associated with fewer post-program arrest and jail days. The target patient population for such programs is typically people with schizophrenia spectrum disorders, but the care of such patients in outpatient settings presents challenges for monitoring treatment fidelity, specifically antipsychotic adherence, as low adherence rates are associated with increased rates of recidivism. Presented here is a review of evidence-based strategies that must be employed to track antipsychotic adherence in outpatient diversion programs, including pill counts, use of long-acting injectable antipsychotics, and determination of plasma antipsychotic levels to assess adherence and the adequacy of antipsychotic treatment. Antipsychotic therapy remains the foundation of schizophrenia treatment, but only through the use of all available modalities can clinicians maximize the odds that schizophrenia patients in pretrial diversion maintain psychiatric stability and successfully complete mental health court mandates.

Practical considerations for managing breakthrough psychosis and symptomatic worsening in patients with schizophrenia on long-acting injectable antipsychotics

With more long-acting injectable (LAI) antipsychotics available for treating schizophrenia, each with variable durations of action (2 weeks to 3 months), it is important to have clear management strategies for patients developing breakthrough psychotic symptoms or experiencing symptomatic worsening on LAIs. However, no treatment guidelines or clinical practice pathways exist; health-care providers must rely on their own clinical judgment to manage these patients. This article provides practical recommendations-based on a framework of clinical, pharmacokinetic, and dosing considerations-to guide clinicians' decisions regarding management of breakthrough psychotic symptoms. Management options include ruling out/addressing medical illness or substance abuse/misuse as a contributing factor, addressing stressors, optimizing nonpharmacologic treatments, treating medical/psychiatric comorbidities, ensuring proper LAI administration technique, addressing missed LAI doses or lack of steady-state attainment, and increasing LAI dose directly or indirectly by shortening the injection interval (off-label). If these strategies do not work sufficiently with frequent monitoring, the LAI could be supplemented with a low dose of the corresponding oral formulation for fast symptom control (off-label). However, caution should be exercised with this strategy, because data on the safety of concomitant use of LAI and oral antipsychotics (OAPs) are limited, especially over extended periods. If symptoms abate, therapy optimization could be continued and slow discontinuation of the OAP could be considered. For persistent/worsening symptoms, the OAP should be increased to optimum effective dose while intensifying the initial steps used before it was added. If this fails, switching the OAP or LAI could be considered. We believe that these strategies will help clinicians manage breakthrough psychotic symptoms during LAI treatment and improve overall outcomes among those who can benefit from LAIs.

Comparison of Paliperidone Palmitate and Second-Generation Oral Antipsychotics in Terms of Medication Adherence, Side Effects, and Quality of Life

PURPOSE

Although schizophrenia can be treated effectively, acute aggravations and relapses occur often. Antipsychotic drug therapies are fairly effective for decreasing the rate of relapses in patients with schizophrenia. This study aimed to compare paliperidone palmitate and the second-generation oral antipsychotic drugs used to treat patients with schizophrenia in terms of medication adherence, side effects, and quality of life.

METHODS

The study included 33 patients diagnosed with schizophrenia who were treated with paliperidone palmitate and 51 patients who were treated with second-generation oral antipsychotics. All the patients were administered the Positive and Negative Syndrome Scale, the Clinical Global Impression, the Extrapyramidal Symptom Rating Scale, the UKU (Ugvalg for Kliniske Undersgelser) Side Effect Rating Scale, the Short Form 36, the Morisky Medication Adherence Scale, and the Schedule for Assessing the Three Components of Insight.

RESULTS

The medication adherence and perceived general health scores of the patients treated with paliperidone palmitate were significantly higher than those of the patients treated with second-generation antipsychotics, and the side effects of the medication on the patients' daily performance were significantly lower.

CONCLUSIONS

This study demonstrated that long-acting paliperidone palmitate therapy was associated with more favorable results in terms of medication adherence, drug side effects, and quality of life compared with second-generation oral antipsychotics. However, there is a need for further, more specific, and larger-scale studies in this field.

Spotlight on once-monthly long-acting injectable aripiprazole and its potential as maintenance treatment for bipolar I disorder in adult patients

The lack of long-term medication adherence is a challenge in the treatment of bipolar disorder, particularly during the maintenance phase when symptoms are less prominent. The rate of nonadherence is ~20%-60% depending on how strict a definition is used. Nonadherence worsens the course of bipolar disorder and can add hundreds of thousands of dollars to the lifetime cost of treating the illness. Long-acting injectable (LAI) medication is an attractive alternative to daily dosing of oral medication, especially among patients who are ambivalent about treatment. The purpose of this paper is to review the evidence for the safety and efficacy of LAI aripiprazole, which was recently approved for the treatment of bipolar disorder. The approval was based on a single double-blind, placebo-controlled, multisite trial that recruited participants from 103 sites in 7 countries. A total of 731 participants with bipolar disorder were enrolled in the study. Out of that total, 266 were successfully stabilized on LAI aripiprazole and entered the randomization phase. Treatment-emergent adverse events were, for the most part, mild to moderate. Akathisia was the most common adverse event, which, combined with restlessness, was experienced by 23% of the sample. At the end of the 52-week study period, nearly twice as many LAI-treated participants remained stable compared to those treated with placebo. Stability during the maintenance phase is arguably the most important goal of treatment. It is during this period of relative freedom from symptoms that patients are able to build a meaningful and satisfying life. The availability of a new treatment agent, particularly one that has the potential to enhance long-term adherence, is a welcome development.

Converting oral to long-acting injectable antipsychotics: a guide for the perplexed

There has been increasing recognition that antipsychotic nonadherence is common across all stages of schizophrenia, starting from the first episode. Moreover, numerous meta-analyses of the existing literature indicate superiority of long-acting injectable (LAI) over oral antipsychotics when one adjusts for the greater illness severity and duration among patients in LAI antipsychotic trials. The increasing availability of LAI antipsychotic options has raised interest in converting patients from oral medication; however, the successful transition from oral to the comparable LAI antipsychotic requires an understanding of the current extent of antipsychotic exposure, the kinetics of the LAI preparation, and the expected plasma levels achieved by the LAI formulation. The purpose of this article is to provide, in a concise format, the essential information for converting patients to the LAI forms of haloperidol, fluphenazine, risperidone, paliperidone, olanzapine, and aripiprazole from the comparable oral medication, and how the use of plasma antipsychotic levels can be invaluable for this process.

Clinical benefits and impact of early use of long-acting injectable antipsychotics for schizophrenia

AIM

Results from clinical trials support the use of oral antipsychotics for treatment of early or first-episode psychosis in patients with schizophrenia. This paper will review literature on the advantages of early initiation of treatment for schizophrenia and the clinical benefits of early use of long-acting injectable antipsychotics (LAIs).

METHOD

A comprehensive literature review was conducted to identify published literature on the use of LAIs early in the treatment of schizophrenia.

RESULTS

Although there is a higher response rate to initial antipsychotic treatment for a first-episode of schizophrenia than with subsequent antipsychotic treatment, we have not effectively addressed this issue. Poor adherence to treatment is a primary cause of relapse and rehospitalization in subsequent years and was associated with higher relapse rates resulting in devastating effects and substantial economic burden. The costs of nonadherence were estimated to be $1.48 billion. Thus, a major challenge with the treatment of schizophrenia is changing poor adherence to persistence with antipsychotic therapy. LAIs are known to be at least as effective as oral antipsychotics for treating schizophrenia, and yet are underutilized. Further, LAIs address many of the problems associated with adherence to oral therapy. Recent evidence suggests that LAIs are effective for treating first-episode psychosis and for early initiation of treatment for schizophrenia.

CONCLUSION

Although consistent antipsychotic treatment represents a critical part of treatment, a person-centred approach to treating schizophrenia is essential for all aspects of care, including establishing and maintaining a therapeutic alliance, strengthening shared decision-making and adherence, and achieving long-lasting recovery.

Haloperidol inactivates AMPK and reduces tau phosphorylation in a tau mouse model of Alzheimer's disease

INTRODUCTION

The use of antipsychotic medications in Alzheimer's disease has been associated with an increased risk of mortality in clinical trials. However, an older postmortem literature suggests that those with schizophrenia treated in an era of exclusively conventional antipsychotic medications had a surprisingly low incidence of tau pathology. No previously published studies have investigated the impact of conventional antipsychotic exposure on tau outcomes in a tau mouse model of AD.

METHODS

In two experiments, transgenic rTg (tauP301L) 4510 tau mice were treated with either haloperidol or vehicle and phosphotau epitopes were quantified using high-sensitivity tau ELISA.

RESULTS

After treatments of 2 and 6 week's duration, mice treated with haloperidol evidenced a significant reduction in tau phosphorylation associated with an inactivation of the tau kinase AMPK.

DISCUSSION

The data suggest that D2 receptor blockade reduces tau phosphorylation in vivo. Future studies are necessary to investigate the impact of this reduction on tau neuropathology.

Comparative effectiveness of long-acting antipsychotics: issues and challenges from a pragmatic randomised study

Although long-acting antipsychotics are widely used in individuals with psychotic disorders, it is unclear which long-acting preparation should be considered as first-line treatment in clinical practice. In this commentary, the main strengths and weaknesses of a recently published pragmatic randomised study comparing long-acting paliperidone palmitate v. long-acting haloperidol decanoate are briefly analysed.

Intramuscular long-acting paliperidone palmitate in acute patients with schizophrenia unsuccessfully treated with oral antipsychotics

In this prospective multicentre, open-label, 6-month study (Paliperidone Palmitate Flexible Dosing in Schizophrenia [PALMFlexS]), tolerability, safety and treatment response with paliperidone palmitate (PP) were explored in patients with acute symptoms of schizophrenia following switching from previously unsuccessful treatment with oral antipsychotics. This pragmatic study was conducted in a large, more representative sample of the general schizophrenia population compared to randomized controlled pivotal trials, to specifically mimic real-world clinical situations. After initiation on Day 1 and Day 8, patients received PP once monthly at flexible doses (50-150mgeq.) intramuscularly. The primary efficacy outcome was defined as the percentage of patients achieving ≥30% improvement in PANSS total score from baseline (BL) to last-observation-carried-forward (LOCF) endpoint (EP). Safety and tolerability assessments included Extrapyramidal Symptom Rating Scale (ESRS) total score and treatment-emergent adverse events (TEAEs). Overall, 212 patients received PP at least once after switching from oral antipsychotics, primarily due to lack of efficacy (45.8%). Significant improvements from BL in mean (SD) PANSS total score were observed from Day 8 onwards (BL to LOCF EP: -31.0 [29.0]; p<0.0001). At endpoint, two-thirds (66.7%) and 43.5% of patients achieved a ≥30% and ≥50% improvement in mean PANSS total score, respectively. PP was associated with significant improvements across secondary measures of symptom severity, subjective well-being, medication satisfaction, illness-related disorders of activity and participation, and patient functioning (p<0.0001; BL to LOCF EP). PP was generally well tolerated, with significant reductions in ESRS total score (p<0.0001) and mainly mild-to-moderate TEAEs. TEAEs reported in ≥5% of patients were injection-site pain (13.7%), insomnia (10.8%), psychotic disorder (10.4%), headache and anxiety (both 6.1%). The PALMFlexS study findings provide valuable pragmatic clinical data on PP treatment in patients with acute schizophrenia previously unsuccessfully treated with oral antipsychotics.

Medication adherence in patients with psychotic disorders: an observational survey involving patients before they switch to long-acting injectable risperidone

BACKGROUND

Maintaining antipsychotic therapy in psychosis is important in preventing relapse. Long-acting depot preparations can prevent covert non-adherence and thus potentially contribute to better patient outcomes. In this observational survey the main objective is to evaluate medication adherence and its determinants for oral treatment in a large sample of patients with psychosis.

METHODS

In this cross-sectional survey medication adherence for oral treatment was assessed by patients using the patient-rated Medication Adherence Questionnaire (MAQ). Data were collected by physicians on patients with a recent acute psychotic episode before switching to long-acting injectable risperidone. Other evaluations included disease severity (Clinical Global Impression - Severity), patients' insight (Positive and Negative Syndrome Scale item G12), treatment acceptance (clinician-rated Compliance Rating Scale), and therapeutic alliance (patient-rated 4-Point ordinal Alliance Scale).

RESULTS

A total of 399 psychiatrists enrolled 1,887 patients (mean age 36.8±11.9 years; 61.6% had schizophrenia). Adherence to oral medication was "low" in 53.2% of patients, "medium" in 29.5%, and "high" in 17.3%. Of patients with psychiatrist-rated active acceptance of treatment, 70% had "medium" or "high" MAQ scores (P<0.0001). Medication adherence was significantly associated with therapeutic alliance (4-Point ordinal Alliance Scale score; P<0.0001). Patient age was significantly associated with adherence: mean age increased with greater adherence (35.6, 36.7, and 38.6 years for patients with "low", "medium", and "high" levels of adherence, respectively; P=0.0007), while age <40 years was associated with "low" MAQ classification (P=0.0003). Poor adherence was also associated with a diagnosis of schizophrenia (P=0.0083), more severe disease (Clinical Global Impression - Severity ≥4; P<0.0001), and lower insight (Positive and Negative Syndrome Scale-G12 ≥4; P<0.0001).

CONCLUSION

Self-reported adherence was low in most patients, with a strong positive association between self-reported adherence and psychiatrists' assessment of treatment acceptance. Understanding factors associated with poor medication adherence may help physicians to better manage their patients, thereby improving outcomes.

A rational approach to employing high plasma levels of antipsychotics for violence associated with schizophrenia: case vignettes

Forensic psychiatric settings contain a high prevalence of treatment-resistant violent schizophrenia patients. Clozapine therapy has the most robust data for the management of violence in patients with schizophrenia, but for those who cannot tolerate or refuse clozapine, high-dose antipsychotic treatment to high achieve high plasma levels remains a viable option despite limited evidence for efficacy in controlled trials. This article enumerates rational guidelines for employing high plasma level strategies, emphasizing the appropriate interpretation of, and reaction to high plasma antipsychotic levels in these treatment resistant patients, and the need to push treatment to the limits of tolerability or clinical response.