Pharmacokinetics of terodiline and a major metabolite in dogs with a correlation to a pharmacodynamic effect

The pharmacokinetics and pharmacodynamics of the anticholinergic and calcium antagonistic drug terodiline, N-tert-butyl-1-methyl-3,3-diphenylpropylamine, have been studied in beagle dogs. The bioavailability was about 25% (0.15 and 0.5 mg/kg), the terminal half-life 3 hr, the systemic clearance 40 ml/min..kg, the volume of distribution (V beta) about 7 l/kg and the unbound fraction in serum 0.14. p-Hydroxyterodiline and p-hydroxy-m-methoxyterodiline were quantitated and constituted 15-40% and 25%, respectively, of the amount excreted in urine (about 60% of the dose) and were the main metabolites, as in man. The dog was used as an experimental model to study the chronotropic effect. An increased heart rate was observed after acute administration of high doses of terodiline as well as after p-hydroxyterodiline. A 20% increase in heart rate was observed at a mean serum concentration of 1086 and 1010 micrograms/l following intravenous injection of terodiline or p-hydroxyterodiline, respectively. The corresponding unbound concentrations were 150 and 474 micrograms/l. The potency ratios of terodiline/p-hydroxyterodiline was 0.9 +/- 0.2 (based on total concentrations) and 3.2 +/- 0.8 (based on unbound concentrations). The estimated potency of parent drug and main metabolite and the fact that p-hydroxyterodiline constitutes 10-20% of the terodiline steady-state level in man, indicate that the contribution of the metabolite to the chronotropic effect observed in clinical studies is minor.     

CYP2D6 genotype determination in the Danish population

CYP2D6 genotyping was carried out by XbaI restriction fragment length polymorphism analysis and polymerase chain reaction in 168 healthy Danish volunteers, 77 extensive metabolizers (EM) and 91 poor metabolizers (PM) of sparteine. All EM were genotyped correctly as heterozygous or homozygous for the functional (wild type) gene, D6-wt. However, the D6-wt gene was apparently also present in 11 (12%) of the PM who accordingly were incorrectly genotyped as EM. The specificity of genotyping PM thus was 100% but the sensitivity was only 88%. The most common allele was the D6-wt with an apparent frequency of 0.741 (0.026) in the Danish population and the second most common allele was the D6-B with an apparent frequency of 0.194 (0.024). The median (range) of the sparteine metabolic ratio (MR) in 47 homozygous D6-wt EM was 0.28 (0.11–4.10) and the corresponding value in heterozygous EM was 0.36 (0.11–9.10). The median difference was 0.09 (95% confidence interval: 0.02–0.16). CYP2D6 phenotyping is a promising tool in tailoring the individual dose of tricyclic antidepressants, some neuroleplics and some antiarrhythmics. However if the genotype test could be improved with regard to both sensitivity in PM and the ability to predict CYP2D6 activity in EM then it would be of even greater clinical value in therapeutic drug monitoring.     

The biology of breast tumor progression. Acquisition of hormone independence and resistance to cytotoxic drugs.

Many breast tumors appear to follow a predictable clinical pattern, being initially responsive to endocrine therapy and to cytotoxic chemotherapy but ultimately exhibiting a phenotype resistant to both modalities. Using the MCF-7 human breast cancer cell line as an example of an 'early' phenotype (estrogen and progesterone receptor positive, steroid responsive, low metastatic potential), we have isolated and characterized a series of hormone-independent but hormone-responsive variants (MIII and MCF7/LCC1). However, these variants remain responsive to both antiestrogens and cytotoxic drugs (methotrexate and colchicine). MIII and MCF7/LCC1 cells appear to mimic some of the critical aspects of the early progression to a more aggressive phenotype. An examination of the phenotype of these cells suggests that some hormone-independent breast cancer cells are derived from hormone-dependent parental cells. The development of a hormone-independent phenotype can arise independently of acquisition of a cytotoxic drug resistant phenotype.     

An anti-CD44 antibody does not enhance engraftment of DLA-identical marrow after low-dose total body irradiation

920 cGy total body irradiation (TBI) is adequate for consistently successful engraftment of marrow from dog leukocyte antigen (DLA)-identical littermates; however, the dose is inadequate to ensure a marrow graft from DLA-nonidentical unrelated donors. Such mismatched grafts are successful only after 1800 cGy, given in three fractions. While anti-T-cell reagents enhance engraftment of DLA-identical littermate marrow after 920 cGy, they fail to be effective in the DLA-nonidentical setting. However, a monoclonal antibody (mAb) to CD44, S5, was found to be very effective in enhancing engraftment of DLA-nonidentical marrow. The current study asked whether mAb S5 was also effective in the setting of DLA-identical littermate transplants. To this purpose, the TBI dose was lowered to 450 cGy, a dose after which 70% of such grafts failed. Four dogs were treated with antibody S5, 0.2 mg/kg on days −7 though −2 (per previously published protocol), given 450 cGy TBI followed by marrow grafts from their DLA-identical littermates. All four dogs rejected their grafts; two of these died from marrow aplasia, and two survived with endogenous marrow recovery. This result was not statistically significantly different from that in 17, historical (n = 5) and concurrent (n = 12), control dogs where 11 of 17 animals rejected. Even if ten experimental animals were transplanted and all six remaining dogs engrafted, the results still would not have been significantly different from control. This result is in contrast to the successful engraftment promoted by pretreatment with antibody S5 of DLA-nonidentical unrelated dogs, consistent with the notion that different host cells are involved in graft rejection in the two disparate histocompatibility settings.     

The angiotensin II type 1-receptor blocker candesartan increases cerebral blood flow, reduces infarct size, and improves neurologic outcome after transient cerebral ischemia in rats.

The goal of the present study was to test the impact of administration time of the angiotensin II type 1-receptor blocker candesartan on cerebral blood flow (CBF), infarct size, and neuroscore in transient cerebral ischemia. Therefore, 1-hour middle cerebral artery occlusion (MCAO) was followed by reperfusion. Rats received 0.5-mg/kg candesartan intravenously 2 hours before MCAO (pretreatment), 24 hours after MCAO, every 24 hours after MCAO, or 2 hours before and every 24 hours after MCAO. Infarct size (mm3) and a neuroscore at day 7 were compared with controls. CBF was quantified by radiolabeled microspheres and laser-Doppler flowmetry. Compared with controls (95 +/- 8), infarct size in candesartan-treated groups was smaller (59 +/- 5, 68 +/- 10, 28 +/- 3, and 15 +/- 3, respectively; P<0.05). Although there was no difference in neuroscore between pretreatment and controls (1.55 +/- 0.18, 1.80 +/- 0.13), other treatment regimens resulted in improved neuroscores (1.33 +/- 0.16, 1.11 +/- 0.11, 0.73 +/- 0.15; P<0.05). CBF in pretreated animals at 0.5 hours after MCAO was significantly higher than in controls (0.58 +/- 0.09 mL x g(-1) x min(-1) and 44% +/- 7% of baseline compared with 0.49 +/- 0.06 mL x g(-1) x min(-1) and 37% +/- 6%, microspheres and laser-Doppler flowmetry; P<0.05). Thus, candesartan reduces infarct size even if administered only during reperfusion. Apart from pretreatment, other treatment regimens result in significantly improved neuroscores. In the acute phase of cerebral ischemia, candesartan increases CBF.     

Lack of stereoselectivity in the inotropic and phosphodiesterase inhibitory effects of saterinone enantiomers

The enantiomers of the positive inotropic and a1-adrenoceptor blocking agent saterinone (+/-)-1,2-dihydro-5-[4-[2-hydroxy-3- [4-(2-methoxyphenyl)-1-piperazinyl]propoxy] phenyl]-6-methyl-2-oxo-3-pyridine-carbonitrile, BDF 8634) have been investigated with in vitro and in vivo models in laboratory animals. In the guinea pig papillary muscle, saterinone enantiomers had equipotent inotropic activity and were also as potent as racemic saterinone; the (R)-enantiomer, however, exhibited a greater efficacy than the related compounds. Saterinone and its enantiomers were equipotent in the inhibition of phosphodiesterase PDE III activity in the guinea pig myocardium. The equipotent inotropic effects were also observed after parenteral and enteral administration in cats. In receptor binding studies, (S)-saterinone was 10-fold more potent than (R)-saterinone by inhibiting [3H]-prazosin binding to specific alpha 1-adrenoceptor sites in rat brain cortex membranes. However, in the isolated thoracic aorta of the rabbit, (S)-saterinone was only 3-fold more potent than (R)-saterinone at preventing the pressor effects of phenylephrine. When the enantiomers were tested in vivo against the pressor effects of phenylephrine in the pithed rat, (S)-saterinone was only 2-fold more potent than (R)-saterinone in its alpha 1-adrenoceptor blocking potency. Thus the enantiomers of saterinone do not display enantio-selectivity in their inotropic and PDE III inhibitory effects in vitro, nor in their cardiotonic effects in vivo. There is a slight enantio-selectivity at alpha 1-adrenoceptors in receptor binding studies, but this is reduced to biologically irrelevant magnitude in functional studies in vitro and in vivo.     

Prevalence of traumatic injuries to the permanent incisors in candidates for orthodontic treatment

Abstract  – The dental records made on presentation of 1367 consecutive patients (731 females and 636 males) for orthodontic treatment at a private orthodontic practice between 1998 and 2002 were examined for data relating to trauma to the permanent incisors. The results showed that 10.3% of these patients had suffered from dental trauma before the onset of orthodontic treatment. The highest prevalence of dental trauma was determined in the 11–15 years age group, corresponding to the dental developmental stage of the late mixed dentition. The most frequently affected teeth were the maxillary central incisors (79.6%), and the most common types of trauma were fracture of enamel–dentin without pulpal involvement (42.7%) and fracture of enamel (33.8%). Compared to patients with normal overjet and adequate lip coverage, the frequency of dental trauma was significantly higher in patients with increased overjet and adequate lip coverage ( P  = 0.028) or with increased overjet and inadequate lip coverage ( P  = 0.003). The results of the present study indicate that a significant percentage of candidates for orthodontic treatment, and especially those with increased overjet and inadequate lip coverage, suffer trauma to their permanent incisors before the onset of orthodontic treatment. It might also be concluded that preventive orthodontic treatment of such patients should be initiated and completed before the age of 11, i.e. in the early to middle mixed dentition.     

Lipid-drug conjugate nanoparticles of the hydrophilic drug diminazene-cytotoxicity testing and mouse serum adsorption.

Sleeping sickness is a widely distributed disease in great parts of Africa. It is caused by Trypanosoma brucei gambiense and rhodiense, transmitted by the Tse-Tse fly. After a hemolymphatic stage, the parasites enter the central nervous system where they cannot be reached by hydrophilic drugs. To potentially deliver the hydrophilic antitrypanosomal drug diminazene diaceturate to the brain of infected mice, the drug was formulated as lipid-drug conjugate (LDC) nanoparticles (NP) by combination with stearic- (SA) and oleic acid (OA). To estimate the in vivo compatibility, the particles were incubated with human granulocytes. Because as potential delivery mechanism the absorption of specific serum proteins (ApoE, Apo AI and Apo AIV) was found to be responsible for the delivery of nanoparticles to the brain, demonstrated using PBCA nanoparticles coated with polysorbate 80 (LDL uptake mechanism) the nanoparticles were incubated with mouse serum and the adsorption pattern was determined using the 2-D PAGE technique. As a result of this study, the cytotoxic potential was shown to decrease when diminazene is part of the particle matrix compared to pure fatty acid nanoparticles and the mouse serum protein adsorption pattern differs from the samples studied earlier in human serum. Especially, the fact concerning Apo-E that could be detected when the particles were incubated in human serum is absent after the mouse serum incubation, potentially, is a critical point for the delivery via the LDL-uptake mechanism but the data demonstrate that LDC nanoparticles, with 33% (wt/wt) drug loading capacity possess the potential to act as a delivery system for hydrophilic drugs like diminazene diaceturate and that further studies have to demonstrate the usability as a brain delivery system.