Deferasirox at therapeutic doses is associated with dose-dependent hypercalciuria.

Deferasirox is an oral iron chelator used widely in the treatment of thalassemia major and other transfusion-dependent hemoglobinopathies. Whilst initial long-term studies established the renal safety of deferasirox, there are now increasing reports of hypercalciuria and renal tubular dysfunction. In addition, urolithiasis with rapid loss of bone density in patients with ß thalassemia major has been reported. We conducted a cross-sectional cohort study enrolling 152 adult patients comprising of ß thalassemia major (81.5%), sickle cell disease (8%), thalassemia intermedia (2%), HbH disease (6.5%) and E/ß thalassemia (2%). Cases were matched with normal control subjects on age, gender and serum creatinine. Iron chelator use was documented and urine calcium to creatinine ratios measured. At the time of analysis, 88.8% of patients were receiving deferasirox and 11.2% were on deferoxamine. Hypercalciuria was present in 91.9% of subjects on deferasirox in a positive dose-dependent relationship. This was not seen with subjects receiving deferoxamine. At a mean dose of 30.2±8.8mg/kg/day, deferasirox was associated with an almost 4 fold increase in urine calcium to creatinine ratio (UCa/Cr). Hypercalciuria was present at therapeutic doses of deferasirox in a dose-dependent manner and warrants further investigation and vigilance for osteoporosis, urolithiasis and other markers of renal dysfunction.

Assessment of aminoglycoside dosing and estimated glomerular filtration rate in determining gentamicin and tobramycin area under the curve and clearance.

BACKGROUND: Aminoglycoside clearance depends on kidney function, but the Australian Therapeutic Guidelines for antibiotics (version 14, 2010) recommend initial dosing based on weight without consideration of kidney function. Other guidelines that modify dosing based on kidney function estimates often use the Cockroft-Gault equation, but the role of the estimated glomerular filtration rate equations for this purpose is unclear. AIM: To determine the performance of current guideline dosing in achieving target area-under-the-curve and examine the relative precision of the estimated glomerular filtration rate equations compared with traditional Cockroft-Gault creatinine clearance in predicting aminoglycoside clearance. METHODS: We analysed 496 aminoglycoside treatment episodes involving 1377 infusions in adult patients. Conformity with antibiotic guideline dosing was achieved if the discrepancy between prescribed and recommended dose was less than 15%. Aminoglycoside clearance was determined from linear regression using a one compartment model with the Aminoglycoside Levels and Daily Dose Indicator programme. We assessed the precision of the Cockroft-Gault, Modification of Diet in renal Disease Study and Chronic Kidney Disease-Epidemiology Collaboration (CKD-EPI) equations in predicting aminoglycoside clearance by correlation and linear regression. RESULTS: Conformity with guideline dosing was not associated with achieving target area-under-the-curve. The CKD-EPI estimated glomerular filtration rate adjusted for body surface area showed the highest correlation (gentamicin, r = 0.66; tobramycin, r = 0.82) and best predictive model for aminoglycoside clearance. CONCLUSION: Current guideline dosing may be suboptimal for achieving target area-under-the-curve. The CKD-EPI equation adjusted for patient body surface area best predicts aminoglycoside clearance, and could be evaluated as a covariate in determining initial aminoglycoside dosing.

Ultraviolet Resonance Raman spectroscopy used to study formulations of salmon calcitonin, a starch-peptide conjugate and TGF-ß3.

Ultraviolet Resonance Raman (UVRR) spectroscopy with excitation at 244 nm was investigated here as a possible useful tool for fast characterization of biopharmaceuticals. Studies were performed on three protein drugs: salmon calcitonin (sCT), starch-peptide conjugate, and transforming growth factor-ß3 (TGF-ß3) adsorbed onto solid granules of tricalcium phosphate (TCP). Secondary structure of sCT was investigated for solutions of 0.5mg/mL up to 200mg/mL, regardless of the turbidity or aggregation states. An increase in ß-sheet content was detected when sCT solutions aggregated. UVRR spectroscopy also detected a small amount of residual organic solvent in a starch-peptide conjugate solution containing only 40 µg/mL of peptide. UVRR spectroscopy was then used to characterize a protein, TGF-ß3, adsorbed onto solid granules of TCP at 50 and 250 µg/cm(3). This study shows that UVRR is suitable to characterize the protein formulations in a broad range of concentrations, in liquid, aggregated, and solid states.

Chemotherapy delays progression of motor neuron disease in the SOD1 G93A transgenic mouse.

BACKGROUND: A significant proliferation of glial cells occurs in the spinal cord and brainstem of SOD1 G93A transgenic mice with familial amyotrophic lateral sclerosis (ALS). Since activated glia may contribute to motor neuron degeneration, we tested whether inhibition of gliosis using low-dose chemotherapy is beneficial in this mouse model. METHODS: Mice were administered fortnightly intraperitoneal injections of 0.1 mg/kg vincristine (VIN) or saline commencing at postnatal day 68 before disease onset. Mice were sacrificed at end-stage disease, and spinal cords were examined for histology. RESULTS: Survival of VIN-treated mice was significantly increased at 132.0 +/- 4.1 days compared to control animals at 117.8 +/- 2.1 days (p < 0.05). Furthermore, analysis of microglia and astrocyte populations suggests a reduction in the former following VIN therapy. CONCLUSION: This study suggests that chemotherapy may offer an alternative therapy or co-therapy for ALS.

Intermittent subcutaneous apomorphine injection treatment for parkinsonian motor oscillations.

Eight patients with severe Parkinsonian motor oscillations have been treated with the dopamine receptor agonist apomorphine by intermittent subcutaneous self-injection as an adjunct to oral anti-Parkinsonian medication. The dopamine receptor antagonist domperidone was also given by mouth to prevent nausea. Six patients remain on chronic treatment (mean period 6.5 months) with improved control of motor function in each case. Four have had major enhancement of their quality of life. Benefits of this treatment stem from the training of patients to use intelligent behaviour to administer a promptly acting and effective pharmacological agent, thereby exercising a degree of direct control over previously unpredictable variations in motor performance.

Evaluation of angiotensin converting enzyme (ACE) in the pharmacokinetics and pharmacodynamics of ACE inhibitors.

The increasing number of angiotensin converting enzyme (ACE) inhibitors means that compounds with different enzyme kinetics, pharmacokinetics, bioavailability, and pharmacodynamics will appear. They will, however, all inhibit ACE, and their hypotensive effect will be a consequence of this action. Enalapril (MK-421) is an esterified prodrug, which in man is converted by the liver to the bioactive potent ACE inhibitor enalaprilate (enalaprilic acid, MK-422). This probably accounts for the slower plasma appearance of MK-422 and the longer duration of action of enalapril. The clinical significance of deesterification by the liver needs further study but minor abnormalities of liver function, such as occur in congestive heart failure, do not affect the rate of deesterification and hence the plasma enalaprilat levels. A close relationship between the plasma drug level, degree of ACE inhibition, and the hormonal and hypotensive effect can be demonstrated after both acute and chronic enalapril administration to hypertensive patients. Chronic therapy with enalapril leads to induction of ACE but in humans this is not sufficient to lead to resistance or tolerance to the drug. Enalapril offers an exciting new approach to the treatment of hypertension with some distinct advantages over conventional antihypertensive therapy.

Enalapril (MK421) activation in man: importance of liver status.

The in vitro conversion of enalapril (MK421) to enalaprilic acid (MK422) in human autopsy tissues was examined. MK422 was measured by radioimmunoassay. Human cadaver liver was the only tissue in which significant conversion was demonstrated. The esterase activity was stable after post mortem. Autopsy liver tissues from patients with elevated ante mortem liver function tests were found to have a reduced rate of deesterification.

Plasma enalapril levels and hormonal effects after short- and long-term administration in essential hypertension.

Enalapril lowers blood pressure both acutely and during long-term therapy in patients with essential hypertension. After a single 10 mg dose of enalapril a close relationship between plasma enalaprilic acid (MK-422) levels, angiotensin converting enzyme (ACE) inhibition and the acute hypotensive and hormonal effects was demonstrated. During long-term administration of enalapril, a similar relationship between the plasma enalaprilic acid level, ACE inhibition and the hypotensive effect was shown, although the dose-response curve for plasma enalaprilic acid to ACE inhibition was displaced to the right compared to the acute dose-response curve. Several weeks' administration of enalapril was needed to reach stable plateau levels of plasma enalaprilic acid and ACE inhibition. During long-term treatment with enalapril in essential hypertension, there was sustained inhibition of ACE and the associated hormonal changes.