Therapeutic drug monitoring of olanzapine: Easy and reliable method for clinical correlation.

AIM: The current work establishes an easy, reliable technique for the estimation of serum Olanzapine concentration which correlates it clinically. SUBJECTS AND METHODS: The work was agreed in 61 schizophrenic patients who were on olanzapine. Serum drug amount was estimated by normal-phase high-performance liquid chromatography and brief psychiatry rating scale was used to determine disease progression.
RESULTS: Samples provided 61 patients, 40 were under sub-therapeutic range, 18 were under therapeutic range and 3 were above the therapeutic range.
CONCLUSION: Therapeutic drug monitoring must be a part of clinical practice in psychiatric hospitals for optimizing the dose of an individual patient along with the correlation of serum concentration with the clinical assessment scales.

Introduction

Olanzapine is benzodiazepine derivative which is used in the management of schizophrenia and also to treat modest to severe mania allied with manic depressive psychosis. Olanzapine was widely biotransformed in the hepatocyte, mainly through direct glucuronidation and CYP1A2 mediated oxidation followed by a lesser extent with CYP2D6. Olanzapine (5–20 mg) is recommended daily dose for schizophrenic patients.[1]

Therapeutic drug monitoring (TDM) of narcoleptics choose to optimize dosage decisions to maximize effectiveness and stop unwanted effects, particularly while those are nonresponsive to management or exposed to undesirable effects through usual quantity for the reason that of demographic, illness, or treatment reciprocal action make difficult in treatment. TDM-assisted psychiatric treatment, while practice by physicians who have background of pharmacokinetics, is potentially useful and cost-effective. TDM is useful in determining drug noncompliance which is a major issue in psychiatric treatment. In many psychiatric hospitals, disease progression is assessed by using different psychiatric rating scales. This is widely used for initially diagnosed and relapse patients.[2]

Due to these reasons, there is a need to develop an easy and reliable method for determining serum Olanzapine concentration which can be utilized in any tertiary care hospital. The earlier available techniques used electrochemical finding, so everyone cannot afford.[34] Even there are some which used ultraviolet (UV) detection, but it is not useful for simultaneous estimation of Olanzapine and risperidone.[56] Along with this, the psychiatric assessment scale is used to correlate TDM results for clinical use. The reported method had a very small sample which does not draw any conclusion.[7]

The main aim of the present study is to develop an easy, reliable high-performance liquid chromatography (HPLC) method for the determination of serum Olanzapine concentration and to correlate it clinically.

Experimental

Chemicals

Olanzapine [Figure 1] and risperidone (internal standard [IS]) were obtained from a local pharmaceutical company. HPLC grade methanol, acetonitrile, and potassium dihydrogen ortho-phosphate were purchased from Rankem Industries PVT Ltd. HPLC grade water was purchased from Fischer-Scientifics.

Figure 1

Chemical structure of olanzapine

Drug preparations

Olanzapine stock solution is done using 10 mg of olanzapine in 10 ml of ACN-water (1:1). Working standard solutions were further prepared to concentrations of 10 μg/ml. IS stock solutions were prepared with methanol. Stock and working solutions should be safe at 4°C up to 7 days. Three healthy volunteers were encouraged to donate the plasma which is drug free and it is utilized to gain the strategy.

Extraction procedure

50 μl of working IS (1 μg/ml) was added to 10 μl serum and briefly mixed with vortex. To this 100 μl of methanol was added, mixed with vortex and centrifuged at 10,000 rpm for 10 min in an Eppendorf centrifuge. The acquired supernatant was gathered and about 15 μl of supernatant was infused into the HPLC framework.

Chromatographic conditions

The chromatographic analysis should be performed with Shimadzu (Kyoto, Japan) system consisting of an LC 20AD reciprocating pump attached with a manual injector (Rheodyne 7725i) by a 50 μl permanent ring, a model SPD 20 A UV-VIS sensing element among uneven wavelength adjust on 235 nm. This whole system is interlinked to a computer which is containing an LC solution 1.25 software (Shimdazu).

The chromatographic portion was done on a Varian Microsorb 100-5 C8 analytical column (250 mm × 4.5 mm). The mobile phase having of potassium dihydrogen orthophosphate buffer and methyl alcohol 60:40 v/v with pH 3.0 adjusted through orthophosphoric acid. The degassed mobile phase is used at a rate of 1.2 ml/min.

Study design

A nonrandomized, interventional investigation of TDM for patients recommended with Olanzapine and a clinical meeting evaluation at the time of TDM. The study design was inspected and endorsed by KIEC (Ethics Committee of KMC) Warangal was inspected and endorsed by the Kakatiya Institutional Ethics Committee and the endorsement number was KIEC/KMC/NCT/NIS/2018/P26.

Sample setting

Patients were recruited basing study criteria. Inclusion strategies: patients whose age is between 18 and 60 years with acute psychiatric symptoms and diagnosed with schizophrenia, olanzapine was initiated in these patients with recurrence of symptoms. Exclusion criteria: other psychotic illness, pediatric, geriatric, pregnant, and lactating women.

Patients were recruited from a tertiary care teaching hospital from Warangal with a sample size of 61, of which 29 were males and 32 were females.

Results and Discussion

Chromatogram

The test run session is 11 min and medications were very much settled at maintenance seasons 3.35 for olanzapine and 9.07 min for risperidone. A chromatogram blank serum spiked with a known concentration of olanzapine and risperidone is shown in Figure 2a. The chromatogram of patient serum treated with Olanzapine is shown in Figure 2b.

Figure 2

Chromatograms of (a) blank serum spiked with a known concentration of olanzapine and risperidone; (b) patient serum treated with olanzapine

Serum concentrations and assessment of brief psychiatry rating scale in patients

The therapeutic range of olanzapine was found to be 20–40 ng/ml, and adverse effects are observed at a concentration above 80 ng/ml. The concentration above 100 ng/ml is considered a therapeutic alert range.

The serum concentrations of Olanzapine were analyzed in 61 patients, of whom 40 were under sub-therapeutic range (<20 ng/ml), 18 were under the therapeutic range (20–40 ng/ml) and 3 were above the therapeutic range (>80 ng/ml). The daily dose (median and range) was 10 mg (5–20 mg). The serum olanzapine concentration (mean and range) was 16.34 ng/ml (1.25–92.74 ng/ml).

Patients were assessed through brief psychiatric rating scale at sample withdrawal. The mean and standard deviation of the individual parameter was calculated as shown in Table 1.

Table 1

Mean and standard deviation of Brief Psychiatric Rating Scale

Parameters	Mean	SD
Somatic concern	2.75	1.69
Anxiety	2.41	1.46
Depression	2.49	1.51
Suicidality	1.98	1.30
Guilt	2.03	1.18
Hostility	2.28	1.28
Elevated mood	1.46	0.92
Grandiosity	1.31	0.81
Suspiciousness	2.33	1.48
Hallucinations	2.13	1.42
Unusual thought content	1.38	0.84
Bizarre behavior	1.15	0.51
Self-neglect	1.31	0.87
Disorientation	1.10	0.35
Conceptual disorganisation	1.05	0.22
Blunted effect	1.33	0.81
Emotional withdrawal	1.28	0.82
Motor retardation	1.28	0.76
Tension	1.92	1.19
Uncooperativeness	1.10	0.44
Excitement	1.10	0.47
Distractibility	1.03	0.18
Motor hyperactivity	1.02	0.13
Mannerisms and posturing	1.00	0.00

SD=Standard deviation

Linearity, precision, and accuracy

Blank serum was spiked with Olanzapine at show a discrepancy of 100–800 ng/ml and interprets by the described technique. The typical curve of olanzapine was linear with a coefficient of correlation of 0.997. Formula of the deterioration stripe is y = 153.26x = 384.25.

The between and within-day precision should be evaluated via analyzing empty serum by various amounts of Olanzapine. Table 2 shows inter-day variation was <6%. Accuracy, as shown in Table 3 ranged from 96% to 102%. The present technique has comparable between day variation to the regular phase HPLC-UV method of Olesen and Linnet[5] and reverse-phase HPLC-UV technique of Dusci et al.[6]

Table 2

Precision of olanzapine in spiked serum

Olanzapine (ng/ml)	Intra-day Coefficient of Variation (%)	Inter-day Coefficient of Variation (%)
150	9.5	5.06
350	4.6	4.3
450	4.4	4.01

Table 3

Accuracy of olanzapine in spiked serum

Concentration (ng/ml)	Accuracy (%)
50	96
250	102.2
550	99.3

Limit of quantification and limit of detection

The limit of detection (LOD) 51.74 ng/ml and the limit of quantification (LOQ) were 150.34 ng/ml, respectively. The present study consists of equal LOD to the reverse phase HPLC-UV technique of Basavaiah et al.[8]

Conclusion

The present method is sensitive, easy to perform, and accurate. This is a validated method with linearity, precision, accuracy, LOD, and LOQ.

The present study helps in the routine estimation of serum olanzapine concentrations. This study also helps clinicians to correlate serum concentrations with clinical assessment scales for disease progression. In this study, we have used BPRS for the assessment of disease progression. This correlation helps in the determination of serious side effects. The patients with serum concentration above 80 ng/ml were found to have motor effects. Weight gain is a common side effect in patients on olanzapine treatment. It is observed that patients with serum concentrations ranging from 20 to 40 ng/ml were found to have weight gain. Patients with serum concentrations <20 ng/ml were predominantly found to have positive symptoms. Patients habituated to smoking found to have low serum concentrations. The method is useful for the estimation of serum concentrations of olanzapine regularly. The present study helps to correlate TDM results with clinical assessment scales which help clinicians to have a better idea on patient condition and optimize treatment.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.