Human experimental pain models: A review of standardized methods in drug development.

Human experimental pain models are essential in understanding the pain mechanisms and appear to be ideally suited to test analgesic compounds. The challenge that confronts both the clinician and the scientist is to match specific treatments to different pain-generating mechanisms and hence reach a pain treatment tailored to each individual patient. Experimental pain models offer the possibility to explore the pain system under controlled settings. Standardized stimuli of different modalities (i.e., mechanical, thermal, electrical, or chemical) can be applied to the skin, muscles, and viscera for a differentiated and comprehensive assessment of various pain pathways and mechanisms. Using a multimodel-multistructure testing, the nociception arising from different body structures can be explored and modulation of specific biomarkers by new and existing analgesic drugs can be profiled. The value of human experimental pain models is to link animal and clinical pain studies, providing new possibilities for designing successful clinical trials. Spontaneous pain, the main compliant of the neuropathic patients, but currently there is no human model available that would mimic chronic pain. Therefore, current human pain models cannot replace patient studies for studying efficacy of analgesic compounds, although being helpful for proof-of-concept studies and dose finding.

Phase 0 - Microdosing strategy in clinical trials.

Drug development is an activity that is long, complex and expensive. In 2004, attrition in the drug development paradigm prompted the US Food and Drug Administration (FDA) to introduce its 'Critical Path' document, which highlighted the serious discordance between major scientific advances and limited drug development process. One issue addressed was that of microdosing. The concept of microdosing involves the use of extremely low, nonpharmacologically active doses of a drug to define the pharmacokinetic profile of the medication in human subjects. Microdosing, thus, appears as a new viable concept in the 'toolbox' of the drug development activity. It appears that microdosing strategy could complement standard animal-to-human scaling, redefining the existing concept of phase I clinical research. In future, when research methods and technology involved in Phase 0 studies become more sophisticated, human microdosing may be applied to a number of drugs developed subsequently.

Calcineurin activity in children with Mental handicap.

Calcineurin, a Ca(2+)-Calmodulin dependent protein phosphatase, is important for Ca(2+) mediated signal transduction. The main objective of this study was to examine the potential role of calcineurin in idiopathic mental handicap. Calcineurin levels were estimated in 20 children in the age group of 5-16 years with idiopathic mental handicap attending the Special. Education Centre for the Mentally Handicapped in Hyderabad. The results of the present study showed decreased activity of serum calcineurin in children with idiopathic mental handicap compared to those of normal subjects in the same age group. The observations thus suggest impaired calcineurin activity in children with mental handicap. Calcineurin that is involved in biosynthesis and release of neurotransmitters at the synaptic terminal brain is affected thereby causing brain damage and leading to mental handicap. Impaired calcineurin activity was already indicated in many human diseases such as Down's syndrome, Alzheimers, Brain ischemia, cardiac hypertrophy etc. It is therefore necessary to check the calcineurin levels in children with mental handicap to understand the role of calcineurin in the causation of Mental handicap.

A randomised, double-blind, parallel, placebo-controlled study to evaluate the efficacy of MF 5232 (Mucotrol), a concentrated oral gel wafer, in the treatment of oral mucositis.

OBJECTIVE: Oral mucositis is a major complication of cytotoxic chemotherapy and radiotherapy associated with significant morbidity, pain, odynophagia, dysgeusia and subsequent dehydration and malnutrition, and effective prophylaxis and/or treatment of this condition is essential. The currently available palliative treatment shows improvement only in patients with mild to moderate mucositis. The primary aim of this study was to compare the clinical efficacy of MF 5232 (Mucotrol), a concentrated oral polyherbal gel wafer formulation, with placebo in the management of chemoradiation-induced mucositis in cancer patients. PATIENTS AND DESIGN: In this randomised, double-blind, pilot study a total of 30 patients of either sex with chemoradiation-induced oral mucositis were randomised to receive MF 5232 (n = 15) or a matching placebo (n = 15) after food three times a day for 7-10 days. Patients were evaluated using validated and standardised scoring systems at baseline and after 7-10 days of treatment. RESULTS: There were 11 evaluable patients in each treatment group. There was a significant reduction in mean mucositis scores with MF 5232 as follows: WHO (from 3.0 to 1.8), Radiation Therapy Oncology Group (gross score: from 2.8 to 1.8; functional score: from 2.9 to 1.0), and Objective Scoring System (ulceration score: from 7.4 to 4.4; erythema score: from 13.7 to 7.0). There were no significant changes in scores for placebo recipients. The treatments were well tolerated, with the exception of two patients in the treatment group who reported a burning sensation in the mouth after dissolving the wafer. CONCLUSION: This pilot study provided positive evidence for the efficacy of MF 5232 therapy in chemoradiation-induced mucositis. This was probably a result of its local analgesic, antioxidant and immunomodulatory activity and wound-healing properties. Further in-depth analysis in a larger number of patients is required to confirm these positive results.

Detection of L1 CAM mutation in a male child with mental retardation.

Recent studies have presented evidence for the involvement of L1CAM gene mutations in various X-linked mental retardation syndromes. The neural cell adhesion molecule, L1CAM is a transmembrane protein belonging to the super family of the immunoglobulins that play a key role in embryonic development of the nervous system and is involved in memory and learning. No studies were carried out from India on L1 CAM gene in X-linked mental retardation syndromes. Hence, an investigation was taken up to delineate the role of L1CAM gene in mental retardation.Two families (Family I and Family II) having only two members affected with mental retardation in each family were studied for mutations in L1CAM gene. In family II, the younger sibling showed deletion involving region between the nucleotide 13,773 (intron 25) and 14,158 (intron 27) region. The mutation what we observed in younger sibling of the family II is a novel mutation which was not hitherto reported in the world literature.

A randomized, double blind, placebo controlled, cross over study to evaluate the analgesic activity of Boswellia serrata in healthy volunteers using mechanical pain model.

OBJECTIVE: Experimental pain models in human healthy volunteers are advantageous for early evaluation of analgesics. All efforts to develop nonsteroidal anti-inflammatory drugs (NSAIDs) which are devoid of gastrointestinal and cardiovascular system effects are still far from achieving a breakthrough. Hence we evaluated the analgesic activity of an ayurvedic drug, Boswellia serrata by using validated human pain models which has shown its analgesic activity both in-vitro and preclinical studies to evaluate the analgesic activity of single oral dose (125 mg, 2 capsules) of Boswellia serrata compared to placebo using mechanical pain model in healthy human subjects. MATERIALS AND METHODS: After taking written informed consent, twelve healthy subjects were randomized (1:1) to receive single oral dose of Boswellia serrata (Shallaki (®)) 125 mg, 2 capsules or identical placebo in a crossover design. Mechanical pain was assessed using Ugo basile analgesymeter (by Randall Selitto test) at baseline and at 1 hr, 2 hrs and 3 hrs after test drug administration. Pain Threshold force and time and Pain Tolerance force and time were evaluated. Statistical analysis was done by paired t-test. RESULTS: Twelve healthy volunteers have completed the study. Mean percentage change from baseline in Pain Threshold force and time with Boswellia serrata when compared to placebo had significantly increased [Force: 9.7 ± 11.0 vs 2.9 ± 3.4 (P = 0.05) and time: 9.7 ± 10.7 vs 2.8 ± 3.4 (P = 0.04)] at third hr. Mean Percentage change from baseline in Pain Tolerance force and time with Boswellia serrata when compared to placebo had significantly (P ≤ 0.01) increased at 1 hr, 2 hrs and 3 hrs. CONCLUSION: In the present study, Boswellia serrata significantly increased the Pain Threshold and Pain Tolerance force and time compared to placebo. Both study medications were well tolerated. Further multiple dose studies may be needed to establish the analgesic efficacy of the drug.

A simple thermal pain model for the evaluation of analgesic activity in healthy subjects.

OBJECTIVE: Assessment of the analgesic effect of an agent in an experimental pain model permits a level of control not possible in a clinical pain setting and is an ideal approach for evaluation of analgesic drugs. The aim of the present study was to establish a simple and reliable method of producing experimental pain, which can be used for screening of various analgesic agents. MATERIALS AND METHODS: The standardized method was followed in all cases, by recording thermal pain threshold in seconds in 24 healthy volunteers using hot air source at two different speeds, which is equipped in an acrylic-made chamber adjustable to three different levels. Reproducibility of the test procedure was evaluated by recording the thermal threshold parameter by a single observer on two sessions (interday reproducibility) and second observer on one session (interobserver reproducibility) separately. Validity of model was further tested by evaluating the analgesic effect of tramadol on 12 healthy volunteers. RESULTS: Thermal pain model was found to produce low variability with coefficient of variation (CV) less than 10%. Interobserver and interday reproducibility were very good, as shown by Bland-Altman plot, with most of the values within ± 2SD. There was a significant increase in pain threshold time with use of tramadol as compared to placebo which was statistically significant (P < 0.05). CONCLUSION: The newly developed pain model offers a stable and sensitive method for the early assessment of analgesic activity.

A simple cold pressure technique for the evaluation of analgesic drugs in healthy subjects.

AIM: An experimental pain model which is sensitive and reproducible would be a useful pharmacological tool both for existing and new drugs. The aim of the present study was to establish a simple and reliable method of producing experimental pain which can be used for screening of analgesic agents. MATERIALS AND METHODS: The method was standardized by recording pain threshold and pain tolerance values in 24 healthy volunteers. Reproducibility of the test procedure was evaluated by recording the pain threshold and pain tolerance values by a single observer on two sessions (inter-day reproducibility), and second observer in one session (inter-observer reproducibility), separately. Validity of the model was further tested by evaluating the analgesic effect of tramadol in 12 healthy volunteers. RESULTS: Cold pain model was found to produce low variability with coefficient of variation less than 15%. Inter-observer and inter-day reproducibility was very good as shown by Bland - Altman plot with most of the values within ± 2SD. Analgesic activity by Tramadol was statistically different from placebo (P < 0.05). CONCLUSION: The newly developed pain model offers a stable and sensitive method for the early assessment of analgesic activity.

Metabolic profiling and biological activities of bioactive compounds produced by Pseudomonas sp. strain ICTB-745 isolated from Ladakh, India.

In an ongoing survey of the bioactive potential of microorganisms from Ladakh, India, the culture medium of a bacterial strain of a new Pseudomonas sp., strain ICTB-745, isolated from an alkaline soil sample collected from Leh, Ladakh, India, was found to contain metabolites that exhibited broad-spectrum antimicrobial and biosurfactant activities. Bioactivity-guided purification resulted in the isolation of four bioactive compounds. Their chemical structures were elucidated by (1)H and (13)C NMR, 2D-NMR (HMBC, HSQC, (1)H,(1)H-COSY, and DEPT- 135), FT-IR, and mass spectroscopic methods, and were identified as 1-hydroxyphenazine, phenazine-1-carboxylic acid (PCA), rhamnolipid-1 (RL-1), and rhamnolipid-2 (RL-2). These metabolites exhibited various biological activities like antimicrobial and efficient cytotoxic potencies against different human tumor cell lines such as HeLa, HepG2, A549, and MDA MB 231. RL-1 and RL-2 exhibited a dose-dependent antifeedant activity against Spodoptera litura, producing about 82.06% and 73.66% antifeedant activity, whereas PCA showed a moderate antifeedant activity (63.67%) at 60 microgram/cm2 area of castor leaf. Furthermore, PCA, RL-1, and RL-2 exhibited about 65%, 52%, and 47% mortality, respectively, against Rhyzopertha dominica at 20 microgram/ml. This is the first report of rhamnolipids as antifeedant metabolites against Spodoptera litura and as insecticidal metabolites against Rhyzopertha dominica. The metabolites from Pseudomonas sp. strain ICTB-745 have interesting potential for use as a biopesticide in pest control programs.

Pharmacodynamic interaction study of Allium sativum (garlic) with cilostazol in patients with type II diabetes mellitus.

AIM: Garlic is available as an over-the-counter herbal supplement and is known to have antiplatelet properties. Because of scarcity of clinical data regarding the safety of concomitant use of garlic supplements and anticoagulants, we tried to evaluate the effects of coadministration of single and multiple doses of garlic and cilostazol on platelet aggregation. MATERIALS AND METHODS: The study was a randomized, open label, placebo-controlled, crossover study of type II diabetic patients, where 14 patients were enrolled and 10 completed the study. The patients were administered 600 mg aged garlic extract, 100 mg cilostazol, 600 mg aged garlic extract, and cilostazol or placebo for seven days as per prior randomization schedule. Blood samples for platelet aggregation and bleeding time and clotting time were collected before and 2, 4, and 6 hours after single-dose drug administration and after seven days of treatment. RESULTS: After single- and multiple-dose administration of garlic, there was a significant inhibition of platelet aggregation at 2 hours, whereas with cilostazol, the inhibition was significant at all the three time points tested, with 4 hours showing maximum inhibition. Coadministration of garlic and cilostazol in single and multiple doses for seven days did not produce any significant change in the antiplatelet activity of the individual drugs. CONCLUSIONS: Coadministration of aged garlic extract and cilostazol did not enhance the antiplatelet activity compared with individual drugs. Large randomized trials are needed to further evaluate the possible interaction of garlic in higher doses and in combination with other antiplatelet activity drugs.

Development of a simple radiant heat induced experimental pain model for evaluation of analgesics in normal healthy human volunteers.

OBJECTIVE: Human experimental pain models help to understand the mechanism of the painful conditions and can also be adopted to test analgesic efficacy of drugs. In early phases, the clinical development of new analgesics is hindered due to the lack of reliable tests for the experimental pain models. In the present study, we have developed and validated a simple radiant heat pain model which can be used for future screening of various analgesic agents. MATERIALS AND METHODS: We have standardized the thermal pain model by recording pain threshold and pain tolerance time in seconds at three different intensities and levels in 24 healthy subjects. Reproducibility of the test procedure was evaluated by recording the pain parameters by two observers on three consecutive days. Validity of model was further tested by evaluating the analgesic effect of tramadol. RESULTS AND CONCLUSIONS: Use of radiant heat pain model with high intensity and short level was found to produce low variability with coefficient of variation less than 5%. Interobserver and interperiod reproducibility was very good as shown by Bland - Altman plot; with most of the values within ± 2SD. Tramadol produced statistically significant increase in pain threshold time. The newly developed pain model produces a type of experimental pain which is responsive to analgesic effects of tramadol at clinically relevant doses.

Clinical and behavioural profile of a rare variant of Klinefelter syndrome-48, XXXY.

Klinefelter's syndrome is a sex chromosomal aneuploidy caused by an addition of X chromosome in males (47,XXY).Variants of this syndrome with X and Y polygamy are of rare occurrence. Here we describe a rare case of 48, XXXY Klinefelter's variant from South India with a reported incidence of 1 per 17,000 to 1 per 50,000 male births. The presence of an extra X chromosome/s in these individuals has a great impact on the physical and cognitive functions, which could be attributed to gene dosage effects and genes involved in neurogenic development.

Immunological studies in children with hearing impairment.

An immunological study was carried out on 58 children below 14 years of age with sensorineural hearing loss of unknown aetiology. The observed elevated levels of IgE in 25.86% (n = 15) children and antinuclear antibodies in 10.34% (n = 6) children indicate that auto-immune activity has a role in the causation of hearing impairment.