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  1. Dhabali AA, Awang R, Hamdan Z, Zyoud SH
    Int J Clin Pharmacol Ther, 2012 Dec;50(12):851-61.
    PMID: 23006441 DOI: 10.5414/CP201689
    OBJECTIVES: The objectives of this study were 1) to obtain information regarding the prescribing pattern of nonsteroidal anti-inflammatory drugs (NSAIDs) in the primary care setting at a Malaysian university, 2) to determine the prevalence and types of potential NSAID prescription related problems (PRPs), and 3) to identify patient characteristics associated with exposure to these potential PRPs.
    METHODS: We retrospectively collected data from 1 academic year using the electronic medical records of patients in the University Sains Malaysia (USM) primary care system. The defined daily dose (DDD) methodology and the anatomical therapeutic chemical (ATC) drug classification system were used in the analysis and comparison of the data. Statements representing potential NSAID PRPs were developed from authoritative drug information sources. Then, algorithms were developed to screen the databases for these potential PRPs. Descriptive and comparative statistics were used to characterize DRPs.
    RESULTS: During the study period, 12,470 NSAID prescriptions were prescribed for 6,509 patients (mean ± SD = 1.92 ± 1.83). This represented a prevalence of 35,944 per 100,000 patients, or 36%. Based on their DDDs, mefenamic acid and diclofenac were the most prescribed NSAIDs. 573 potential NSAID-related PRPs were observed in a cohort of 432 patients, representing a prevalence of 6,640 per 100,000 NSAIDs users, or 6.6% of all NSAID users. Multivariate logistic regression analysis revealed that patients with a Malay ethnic background (p < 0.001), members of the staff (p < 0.001), having 4 or more prescribers (p < 0.001) or having 2 - 3 prescribers (p = 0.02), and representing 4 or more long-term therapeutic groups (LTTGs) (p < 0.001) or 2 - 3 LTTGs (p < 0.001) were significantly associated with an increased chance of exposure to potential NSAID related PRPs.
    CONCLUSIONS: This is the first study in Malaysia that presents data on the prescribing pattern of NSAIDs and the characteristics of potential NSAID-related PRPs. The prevalence of potential NSAID-related PRPs is frequent in the primary care setting. Exposure to these PRPs is associated with specific sociodemographic and health status factors. These results should help to raise the awareness of clinicians and patients about serious NSAID PRPs.

    Study site: University Sains Malaysia (USM) primary care system.
  2. Dhabali AA, Awang R, Zyoud SH
    Int J Clin Pharmacol Ther, 2011 Aug;49(8):500-9.
    PMID: 21781650 DOI: 10.5414/cp201524
    BACKGROUND: The prescription of contraindicated drugs is a preventable medication error, which can cause morbidity and mortality. Recent data on the factors associated with drug contraindications (DCIs) is limited world-wide, especially in Malaysia.

    AIMS: The objectives of this study are 1) to quantify the prevalence of DCIs in a primary care setting at a Malaysian University; 2) to identify patient characteristics associated with increased DCI episodes, and 3) to identify associated factors for these DCIs.

    METHODS: We retrospectively collected data from 1 academic year using computerized databases at the Universiti Sains Malaysia (USM) from patients of USM's primary care. Descriptive and comparative statistics were used to characterize DCIs.

    RESULTS: There were 1,317 DCIs during the study period. These were observed in a cohort of 923 patients, out of a total of 17,288 patients, representing 5,339 DCIs per 100,000 patients, or 5.3% of all patients over a 1-year period. Of the 923 exposed patients, 745 (80.7%) were exposed to 1 DCI event, 92 (10%) to 2 DCI events, 35 (3.8%) to 3 DCI events, 18 (2%) to 4 DCI events, and 33 patients (3.6%) were exposed to 5 or more DCI events. The average age of the exposed patients was 30.7 ± 15 y, and 51.5% were male. Multivariate logistic regression analysis revealed that being male (OR = 1.3; 95% CI = 1.1 - 1.5; p < 0.001), being a member of the staff (OR = 3; 95% CI = 2.5 - 3.7; p < 0.001), having 4 or more prescribers (OR = 2.8; 95% CI = 2.2 - 3.6; p < 0.001), and having 4 or more longterm therapeutic groups (OR = 2.3; 95%CI = 1.7 - 3.1; p < 0.001), were significantly associated with increased chance of exposure to DCIs.

    DISCUSSION AND CONCLUSIONS: This is the first study in Malaysia that presents data on the prevalence of DCIs. The prescription of contraindicated drugs was found to be frequent in this primary care setting. Exposure to DCI events was associated with specific socio-demographic and health status factors. Further research is needed to evaluate the relationship between health outcomes and the exposure to DCIs.
  3. Hassan Y, Al-Jabi SW, Aziz NA, Looi I, Zyoud SH
    Int J Clin Pharmacol Ther, 2011 Oct;49(10):605-13.
    PMID: 21961485 DOI: 10.5414/cp201574
    BACKGROUND: Patients with diabetes mellitus (DM) are more prone to develop atherosclerotic complications including stroke. Moreover, as a primary and secondary prevention of stroke, antiplatelet therapy is recommended by clinical guidelines for patients with DM.

    AIMS: This study aimed to determine the prevalence of antiplatelet therapy use prior to current stroke in diabetic ischemic stroke patients, to examine the factors associated with the use of this important therapy and to assess the impact of the previous use of antiplatelet therapy on ischemic stroke outcomes.

    METHODS: An observational study of diabetic acute ischemic stroke patients attending a Malaysian hospital during a 1-year period was carried out. Demographic information, risk factors, previous antiplatelet use and variables used to assess stroke outcomes were collected from medical records.

    RESULTS: Overall, 295 diabetic stroke patients were analyzed. The prevalence of previous antiplatelet use among diabetic patients was 38.3%. The independent variables associated with the previous use of antiplatelet medication were previous stroke attack (p < 0.001) and ischemic heart disease (p < 0.001). Better outcomes as measured by a minor Glasgow Coma Scale at admission (p = 0.032), and a higher Modified Barthel index at discharge (p = 0.027) were observed among patients on previous antiplatelet therapy.

    CONCLUSION: Our data suggest that antiplatelet therapy is under prescribed among such diabetic stroke patients, particularly in primary prevention. Effective methods to increase antiplatelet use and to enhance the adherence of clinical practice guidelines should be considered at the national and community level.
  4. Miyata-Nozaka Y, Tan HJ, Wong SW, Raymond AA, Omar H, Zain SM
    Int J Clin Pharmacol Ther, 2021 Jan;59(1):8-16.
    PMID: 33026315 DOI: 10.5414/CP203761
    OBJECTIVE: Epilepsy is a common chronic neurological condition characterized by recurrent seizures. Approximately 30 - 40% of epileptic patients do not respond to antiepileptic drugs. Previous studies suggest that CYP3A5 polymorphisms affect carbamazepine metabolism.

    MATERIALS AND METHODS: To examine this hypothesis, in the present study, the associations between CYP3A5 variants (rs776746 and rs1419745) and response to carbamazepine and valproic acid monotherapy in Malaysian epileptic patients were evaluated.

    RESULTS: A total of 288 Malaysian epileptic patients were recruited and further reviewed, of whom 63 patients were on carbamazepine monotherapy, and 85 patients were on valproic acid monotherapy. There was no patient with drug hypersensitivity syndrome within the population. Subjects were genotyped by using Sequenom MassARRAY platform. This study found a significant association of CYP3A5 rs776746 with the carbamazepine treatment response in total patients (p = 0.026) and Malay ethnic subgroup (p = 0.006). In addition, a marginal significant association of CYP3A5 rs1419745 with carbamazepine treatment response was reported in the Malays. Similarly, CYP3A5 rs776746 was associated with valproic acid response in total patients (p = 0.037) and Malays (marginal p = 0.05).

    CONCLUSION: Our findings suggest that CYP3A5 polymorphisms affect carbamazepine and valproic acid response in Malaysian epileptic patients.

  5. Lv X, Zhong G, Yao H, Wu J, Ye S
    Int J Clin Pharmacol Ther, 2021 Nov;59(11):725-733.
    PMID: 34448694 DOI: 10.5414/CP203986
    OBJECTIVE: An earlier three-way crossover study evaluating bioequivalence of 3 cefalexin formulations (capsule for reference, capsule and tablet for test) in healthy subjects in Malaysia showed that the intra-individual coefficients of variation were 9.25% for AUC0-t, 9.54% for AUC0-∞, and 13.90% for Cmax. It is preliminarily stated that cefalexin is not a high-variation product. The here-presented clinical study in China was carried out to analyze the pharmacokinetic properties of two preparations in fasting and postprandial condition to assess the bioequivalence of the test preparation and reference preparation when administered on a fasting and postprandial basis in healthy Chinese subjects and to observe the safety of the test preparation and reference preparation in healthy Chinese subjects.

    MATERIALS AND METHODS: In this trial, a total of 56 eligible subjects were randomly assigned to the fasting group and the postprandial group. The two groups were given 250 mg of the test and reference preparation, respectively. Liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) was applied to determine the plasma concentration of cefalexin. PhoenixWinNonlin software (V7.0) was used to calculate the pharmacokinetic parameters of cefalexin using the non-compartmental model (NCA), and the bioequivalence and safety results were calculated by SAS (V9.4) software.

    RESULTS: The main pharmacokinetic parameters of the test and reference preparations were as follows, the fasting group: Cmax 12.59 ± 2.65 μg/mL, 12.72 ± 2.28 μg/mL; AUC0-8h 20.43 ± 3.47 h×μg/mL, 20.66 ± 3.38 h×μg/mL; AUC0-∞ 20.77 ± 3.53 h×μg/mL, 21.02 ± 3.45 h×μg/mL; the postprandial group: Cmax 5.25 ± 0.94 μg/mL, 5.23 ± 0.80 μg/mL; AUC0-10h 16.92 ± 2.03 h×μg/mL, 17.09 ± 2.31 h×μg/mL; AUC0-∞ 17.33 ± 2.09 h×μg/mL, 17.67 ± 2.45 h×μg/mL.

    CONCLUSION: The 90% confidence intervals of geometric mean ratios of test preparation and reference preparation were calculated, and the 90% confidence intervals of geometric mean ratios of Cmax, AUC0-10h, and AUC0-∞ were within the 80.00% ~ 125.00% range in both groups. Both Cmax and AUC met the pre-determined criteria for assuming bioequivalence. The test and reference products were bioequivalent after administration under fasting as well as under fed conditions in healthy Chinese subjects. This study may suggest that successful generic versions of cefalexin not only guarantee the market supply of such drugs but can also improve the safety and effectiveness and quality controllability of cefalexin through a new process and a new drug composition ratio.

  6. Yuen KH, Wong JW, Billa N, Julianto T, Toh WT
    Int J Clin Pharmacol Ther, 1999 Jul;37(7):319-22.
    PMID: 10442505
    The bioavailability of a generic preparation of metformin (Diabetmin from Hovid Sdn Bhd) was evaluated in comparison with a proprietary product (Glucophage from Lipha Pharma Ltd., UK).
  7. Rahman AR, Lang CC, Struthers AD
    Int J Clin Pharmacol Ther, 1995 Jul;33(7):404-9.
    PMID: 7582398
    Increasing animal evidence support an important facilitatory interaction between angiotensin II and norepinephrine within the kidney. This angiotensin II/norepinephrine interaction was investigated in man by examining the effect of enalapril pretreatment (5 mg for 5 days) on the renal response to a low non-pressor dose of intravenous tyramine 4 micrograms/kg/min for 120 min in 8 healthy subjects undergoing water diuresis. Tyramine is an indirect sympathomimetic agent which causes neuronal release of norepinephrine. Enalapril and tyramine, alone and in combination, had no effect on glomerular filtration, effective renal plasma flow or sodium excretion. Tyramine caused a significant increase in urinary flow rate (p < 0.05) but this was not influenced by enalapril pretreatment. The lack of effect of enalapril on the renal response to tyramine contrasts with a previous study which examined the effect of enalapril on the renal response to circulating norepinephrine. This may suggest that enalapril affect renal function only when there is renal vasoconstriction (as with norepinephrine) and not when renal blood flow is unchanged (as with tyramine).
  8. Xiang YT, Kreyenbuhl J, Dickerson FB, Ungvari GS, Wang CY, Si TM, et al.
    Int J Clin Pharmacol Ther, 2012 Jul;50(7):500-4.
    PMID: 22541750 DOI: 10.5414/CP201683
    This study surveyed the prescribing patterns of antipsychotic medications in Asian older schizophrenia patients with extrapyramidal side effects (EPS) during the period between 2001 and 2009.
  9. Rasool AH, Rehman A, Wan Yusuf WN, Rahman AR
    Int J Clin Pharmacol Ther, 2003 Dec;41(12):587-92.
    PMID: 14692708
    INTRODUCTION: Arterial stiffness is emerging as a useful index of vascular health. Postmenopausal women have been shown to have stiffer arteries. Hormone replacement therapy and soy isoflavones improve arterial stiffness in these women. The aim of this study is to establish whether vitamin E improves arterial stiffness in postmenopausal women after 10 weeks of supplementation.

    METHODS: Twenty postmenopausal women with a mean age of 54.59 +/- 1.22 years participated in this randomized, crossover, double-blind, placebo-controlled clinical trial. All women received 400 IU of tocopherol daily for 10 weeks or a placebo capsule, before being crossed over for treatment. At intervals of 5 weeks, subjects attended sessions where measurements of arterial stiffness, blood pressure and plasma vitamin E level were taken. Pulse wave velocity measurement, using the automated Complior machine, was used as an index of arterial stiffness.

    RESULTS: Plasma vitamin E level was 30.38 +/- 1.56 micromol/l at baseline, after treatment it was 59.01 +/- 3.30 micromol/l and 31.17 +/- 1.37 micromol/l with vitamin E and placebo, respectively (p < 0.001). There was no significant difference in pulse wave velocity after 10-week treatment with placebo and vitamin E (9.14 +/- 0.29 versus 9.04 +/- 0.29 m/s, respectively). Similarly, no difference in systolic and diastolic blood pressure was seen between placebo and vitamin E at the end of 10 weeks.

    CONCLUSION: Supplementary vitamin E for 10 weeks at 400 IU daily has no effect on arterial stiffness in healthy postmenopausal women.

  10. Rehman A, Rahman AR, Rasool AH, Naing NN
    Int J Clin Pharmacol Ther, 2001 Oct;39(10):423-30.
    PMID: 11680667
    To examine the dose response relationship between Ang II and pulse wave velocity (an index of arterial stiffness) in healthy human volunteers.
  11. Tassaneeyakul W, Kumar S, Gaysonsiri D, Kaewkamson T, Khuroo A, Tangsucharit P, et al.
    Int J Clin Pharmacol Ther, 2010 Sep;48(9):614-20.
    PMID: 20860915
    OBJECTIVES: To compare the bioavailability of two risperidone orodispersible tablet products, Risperidone 1 mg Mouth dissolving tablet, Ranbaxy (Malaysia) Sdn. Bhd., Malaysia, as a test product and Risperdal 1 mg Quicklet, Janssen Ortho LLC, Gurabo, Puerto Rico, as a reference product, in healthy male volunteers under fasting condition.

    MATERIALS AND METHODS: A randomized, 2-treatment, 2-period, 2-sequence, single dose, crossover with a washout period of 2 weeks, was conducted in 24 healthy Thai male volunteers. Blood samples were collected at 0, 0.25, 0.5, 0.75, 1, 1.25, 1.5, 1.75, 2, 2.5, 3, 3.5, 4, 5, 6, 8, 10, 12, 24, 36, 48, 72 and 96 h following drug administration. Plasma concentrations of risperidone and 9-hydroxyrisperidone were determined using a validated LC-MS-MS method. The pharmacokinetic parameters of risperidone and 9-hydroxyrisperidone were determined using a non-compartmental model.

    RESULTS: The geometric means ratios (%) and 90% confidence interval (CI) of the test and reference products for the log-transformed pharmacokinetic parameters, Cmax, AUC0-t and AUC0-inf of risperidone were 104.49 % (92.79% - 117.66%), 100.96 % (92.15% - 110.61 %) and 97.99 % (90.72% - 105.85%). The 90% CI of geometric means ratios of the test and reference products for the log-transformed pharmacokinetic parameters, Cmax, AUC0-t and AUC0-inf of 9-hydroxyrisperidone were 97.00%, 96.97% and 97.49%.

    CONCLUSIONS: The 90% CI for the geometric means ratios (test/reference) of the log-trasformed Cmax, AUC0-t and AUC0-inf of risperidone and its major active metabolite were within the bioequivalence acceptance criteria of 80% - 125% of the US-FDA.

  12. Chik Z, Basu RC, Pendek R, Lee TC, Mohamed Z
    Int J Clin Pharmacol Ther, 2009 Jun;47(6):413-8.
    PMID: 19473604
    This study was carried out to compare the rate and extent of absorption of a generic salbutamol in oral dosage form (Brethmol, 4 mg) with the proprietary equivalent product (Ventolin, 4 mg), in healthy adult subjects, under fasting conditions. The study was a single dose, randomized, two way crossover study with a four-week washout period. It involved 22 healthy volunteers who received a single dose (4 mg) of the test and the reference products after an overnight fast of at least 10 hours. Blood samples were collected at pre-dose and a serial of 14 samples were collected from each of the subject from 1 h until 48 h post-dose. Plasma concentrations of salbutamol were analyzed using GCMS method. The mean AUC(0-yen) values were 91.26 and 96.45 h.ng/ml for reference and test product, respectively. The mean C(max) values were 12.26 and 12.38 ng/ml and the mean t(max) values were 2.80 and 2.33 hours for reference and test product, respectively. Analysis of variance showed that the 90% confidence intervals on the relative difference of the ratio for the AUC(0-yen) and the C(max) for the test and reference products were contained within the bioequivalence limit (80 - 125%) (C(max): 89.8 - 110.5% and AUC(0-yen): 91.6 - 121.5%). There was no statistically significant difference for the t(max) between the test and reference formulations (p = 0.30). The test formulation was found to be bioequivalent to the reference formulation with regard to AUC(0-yen) and C(max). There was no statistically significant difference in Brethmol and Ventolin t(max). In conclusion, Brethmol and Ventolin are bioequivalent in healthy subjects.
  13. Rasool AH, Rahman AR, Ismail R, Hatim S, Abdullah AR, Singh R, et al.
    Int J Clin Pharmacol Ther, 2000 May;38(5):260-9.
    PMID: 10839470
    OBJECTIVE: To determine whether racial differences in response to blockade of beta receptors occur among racial groups in Malaysia that are the Malays, Indians and Chinese. SUBJECTS, MATERIALS AND METHOD: 35 healthy male volunteers representing the 3 main racial groups in Malaysia (12 Malays, 12 Chinese and 11 Indians) were studied in a randomized, placebo-controlled, crossover and single-blind design. Propranolol 80 mg 12-hourly was given orally for 48 hours. Six hours after the last dose subjects attended an exercise session where resting and exercise heart rate, blood pressure, plasma potassium and glucose levels, resting FEV1 and plasma propranolol concentrations were recorded.

    RESULTS: No significant difference in plasma propranolol (mean +/- SEM) levels was seen between races six hours after the last dose (Malays, 59.7 +/- 8.8 ng/ml, Indians, 67.6 +/- 19.3 ng/ml, Chinese, 58.4 +/- 7.9 ng/ml). Chinese were least sensitive to the bradycardic and hypotensive effects of propranolol at rest and exercise. Indians and Malays had significant reduction of supine systolic blood pressure with propranolol but not Chinese. Comparison of percentage reductions of systolic blood pressure at supine, sitting and exercise by repeated measure analysis showed the Malays to have significantly higher change compared to the Chinese (p = 0.022). Similarly, comparison of percentage reductions of heart rate at supine, sitting and exercise by repeated measure analysis showed the Malays to have significantly higher change compared to the Chinese (p = 0.040). Average change in potassium concentrations at peak exercise and recovery showed the Indians to have significantly higher increase in potassium levels with propranolol compared to the Malays (p = 0.038). However, no significant interethnic difference was seen in the reduction of glucose levels at rest, peak exercise or recovery. Also, no significant interethnic difference was seen in reduction of FEV1 values.

    CONCLUSION: We, therefore, conclude that ethnic differences in response to blockade of beta-receptors exist among racial groups in Malaysia. These differences were seen at similar plasma drug levels between races suggesting ethnic differences in drug sensitivity, rather than differences in drug disposition.

  14. Hassan Y, Al-Ramahi RJ, Aziz NA, Ghazali R
    Int J Clin Pharmacol Ther, 2010 Sep;48(9):571-6.
    PMID: 20860910
    BACKGROUND AND OBJECTIVE: Adverse drug events (ADEs) are a common cause of hospitalization and in-hospital complications. The aim of this study was to determine the rates, types, severity and preventability of pre-admission and in-hospital ADEs in patients with chronic kidney disease (CKD).

    METHODS: This study was conducted at the nephrology unit at Penang General Hospital. A random sample of 300 adult patients with CKD was included. Medical records and charts were reviewed by a clinical pharmacist every work day to find any evidence of errors or complications related to drug use. If a suspected ADE was found, further investigations were carried out to assess the causality, severity and preventability of the event.

    RESULTS: A total of 159 ADEs were reported in 122 (40.7%) of the patients. We found 86 suspected pre-admission ADEs in 68 (22.7%) of the patients. These were either the cause of admission for some patients or discovered by the initial physical examination and laboratory investigations. During hospitalization, 64 (21.3%) patients had 73 suspected ADEs. Out of the total 159 suspected ADEs, it was highly probable that 31 events were due to medication, while 61 were of lower probability, and 67 were merely possible. A total of 48 (30.2%) events was considered preventable. 46 events (28.9%) were serious, 93 (58.5%) were less serious and 20 (12.6%) were insignificant. The medication classes most frequently involved in ADEs were diuretics, antibacterials, drugs used for diabetes mellitus, antithrombotic agents, mineral supplements and antihypertensive drugs.

    CONCLUSION: ADEs are very common in hospitalized CKD patients, and some of these events are preventable. The service of a clinical pharmacist may help to reduce ADEs.

  15. Habil MH, Gondoyoewono H, Chaudhry HR, Samanwongthai U, Hamid AR, Hashmi IT, et al.
    Int J Clin Pharmacol Ther, 2007 Dec;45(12):631-42.
    PMID: 18184531
    OBJECTIVE: The objective of this study was to assess the effectiveness and safety of olanzapine in the treatment of schizophrenia among Asian patients in an outpatient setting.

    METHODS: This was an open-label, prospective, observational study involving 339 patients from Indonesia, Pakistan, Malaysia, Thailand, and Singapore. Brief Psychiatric Rating Scale (BPRS), Clinical Global Impression Severity scale (CGI-S), and safety parameters were assessed.

    RESULTS: 62% of patients responded to olanzapine treatment, defined a priori as a reduction in BPRS of > 40% from baseline. Following the 8-week treatment period, the BPRS total, BPRS positive, BPRS negative, and CGI-S scores decreased by 18.7 (95% CI: 17.4, 20.2), 6.1 (5.6, 6.6), 2.9 (2.6, 3.2), and 1.5 points (median 1.0), respectively (p < 0.0001). In total, 31 of the 339 patients (9.1%) failed to complete the study according to the study description. Loss to follow-up and personal conflict were the most common reasons for discontinuation. There were 30 treatment-emergent adverse events with six serious cases, assessed as unrelated to study drug, reported.

    CONCLUSION: This study further demonstrates the effectiveness and safety of olanzapine in actual clinical practice settings, in reducing the severity of psychopathological symptoms in Asian patients with schizophrenia.

  16. Yuen KH, Wong JW, Yap SP, Billa N
    Int J Clin Pharmacol Ther, 2001 Jan;39(1):37-40.
    PMID: 11204936
    OBJECTIVE: The aim of the present communication is to provide information regarding the intrasubject coefficent of variation obtained from 30 bioequivalence studies covering 16 drugs which can be used for estimation of sample size. Additionally, an attempt was also made to estimate the test power of each of the studies conducted.

    METHODS: The intrasubject coefficient of variation was estimated from the residual mean square error obtained from analysis of variance of the parameters AUC0-infinity, Cmax and Cmax/AUC0-infinity after logarithmic transformation. The test power in the analyses of the above parameters was subsequently estimated using nomograms provided by Diletti et al. [1991].

    RESULTS AND CONCLUSION: Thirty products covering 16 drugs were studied in which 22 were immediate-release (including one dispersible tablet) and 8 were sustained-release formulations. The intrasubject coefficient of variation for the parameter AUC0-infinity was smaller than Cmax, and hence considerably more studies were able to attain a power of greater than 80% using 12 volunteers for the AUC0-infinity, compared to the Cmax. However, the variability in the Cmax could be reduced by using the parameter Cmax/ AUC0-infinity, and thus, provide a more realistic estimation of sample size, since the latter reflects only the rate of absorption and not both the rate and extent as in the case of Cmax [Endrenyi et al. 1991].

  17. Batra YK, Shamsah M, Al-Khasti MJ, Rawdhan HJ, Al-Qattan AR, Belani KG
    Int J Clin Pharmacol Ther, 2007 Mar;45(3):155-60.
    PMID: 17416110
    OBJECTIVE: Ketamine inhibits the NMDA receptors via non-competitive antagonism, resulting in an antihyperalgesic effect achieved by doses of ketamine much smaller than are required for analgesia. The aim of this study was to determine the extent to which small-dose ketamine, when used in conjunction with remifentanil, has a morphine-sparing effect in the perioperative period.

    MATERIALS AND METHODS: In this randomized, double-blind, placebo-controlled prospective study, we enrolled 40 children undergoing tonsillectomy. Anesthetic care was standardized. Intraoperative analgesia was provided with remifentanil 0.5 microg x kg(-1) followed by an infusion of 0.25 microg x kg(-1) x min(-1). Group I (ketamine, n = 20) received a bolus dose of ketamine 0.5 mg x kg(-1) followed by a continuous infusion of 2 microg x kg(-1) x min(-1) before start of surgery. The infusion was stopped when surgery ended. Group II (placebo, n=20) received normal saline in the same manner. Pain was assessed postoperatively using the Children's Hospital Eastern Ontario Pain Scale (CHEOPS; range of scores 4 13), and total morphine consumption was recorded in the postanesthesia care unit (PACU). Patients were transferred to the ward and morphine was administered via a patient-controlled analgesia (PCA) device and analgesia was recorded using a visual analogue scale (VAS) (0 - 10).

    RESULTS: Intraoperative remifentanil consumption was not different between the ketamine group (0.29+/-0.09 microg x kg x min(-1) ) and the control group (0.24+/-0.07 microg x kg x min(-1)). There were no significant differences between CHEOPS scores and VAS score between the two groups. The total mean morphine consumption in the ward was not significantly different between the two groups: 376.5 +/-91.6 microg x kg(-1) with ketamine and 384.4+/-97.3 microg x kg(-1) with placebo. The time-to-first analgesic requirement was also similar in both groups.

    CONCLUSIONS: Small-dose ketamine did not decrease postoperative pain after tonsillectomy in children when added to a continuous intraoperative remifentanil infusion.

  18. Chik Z, Johnston A, Tucker AT, Kirby K, Alam CA
    Int J Clin Pharmacol Ther, 2009 Apr;47(4):262-8.
    PMID: 19356392
    Circulating concentrations of endogenous compounds such as testosterone, complicate the analysis of pharmacokinetic parameters when these compounds are administered exogenously. This study examines the influence of three correction methods of accounting for endogenous concentrations on the determination of bioequivalence between two testosterone formulations.
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