The preclinical toxicological evaluation of sumatriptan

1995 ◽  
Vol 14 (12) ◽  
pp. 959-973 ◽  
Author(s):  
K. Owen ◽  
K. Hartley ◽  
ML Tucker ◽  
MM Parkinson ◽  
DJ Tweats ◽  
...  
Keyword(s):  
Plasma Concentrations ◽  
Subcutaneous Administration ◽  
Nitroso Compounds ◽  
Facial Oedema ◽  
Corneal Surface ◽  
Toxicological Evaluation ◽  
The Central Nervous System ◽  
Repeated Dosing ◽  
High Doses ◽  
Oral Doses

1 Sumatriptan is a potent and selective 5-HT1 receptor agonist marketed for the treatment of migraine by both oral and subcutaneous routes. An extensive toxicologi cal programme employing high doses of sumatriptan was carried out in a range of animal species. The stud ies evaluated both the local and systemic tolerance to single and repeated dosing, effects on all stages of repro duction, as well as the genotoxic and oncogenic poten tial of sumatriptan. 2 The administration of relatively high single and repeat ed doses of sumatriptan was well tolerated by both rodents and dogs by the oral, subcutaneous and intra venous routes. Behavioural effects, suggestive of involvement of the central nervous system, were the most obvious result of such doses and were generally more pronounced in dogs than rodents. The reason for this may be related to the higher plasma concentrations of the drug achievable in dogs. Additional observations restricted to dogs, were transient, and included tachy cardia, facial oedema and breaks in the continuity of secretion films on the corneal surface. A tendency for an increase in weight gain was seen for rats, while a slight decrease was usually seen for dogs. The only pathologi cal changes related to treatment with high concentra tions of sumatriptan consisted of local reactions at the site of subcutaneous administration. 3 Sumatriptan is an indole; the structures of this chemical class show varying propensities for nitrosation. However, appropriate testing with sumatriptan failed to identify any mutagenic nitroso compounds. 4 Sumatriptan was neither genotoxic nor oncogenic. 5 Reproductive studies demonstrated that sumatriptan was not teratogenic and had no effect on peri- and post natal development. Some embryotoxicity was observed, but only at maternally toxic doses. A slight decrease in the success of insemination was also noted at high oral doses in rats. 6 Results of the toxicological programme performed in support of migraine therapy with sumatriptan provide good assurance of safety for subcutaneous and oral use.

Temelastine, a New H1-Receptor Antagonist

1986 ◽  
Vol 14 (4) ◽  
pp. 200-204 ◽  
Author(s):  
Fred Alexander ◽  
Robert M Stote ◽  
Nancy Allison ◽  
Robert G Familiar ◽  
Dianne Tatoian ◽  
...  
Keyword(s):  
Receptor Antagonist ◽  
Plasma Concentrations ◽  
Controlled Study ◽  
Blood Levels ◽  
Double Blind Study ◽  
Double Blind ◽  
The Central Nervous System ◽  
H1 Receptor Antagonist ◽  
Oral Doses ◽  
Wheal Size

Temelastine is a selective, competitive histamine H1-receptor antagonist which does not penetrate the central nervous system. The effect of varying doses of temelastine was compared in a randomized, double-blind, controlled study by measuring the inhibition of cutaneous histamine wheals. In twelve subjects single oral doses of 50, 100 and 200 mg of temelastine produced dose-dependent reductions in wheal areas. The inhibition of wheal size was maximal by 2 hr after dosing and was present at 8 hr. At 2 hr the 50, 100, and 200 mg doses reduced the wheal size by 53, 64, and 78%, respectively. Chlorpheniramine, 4 mg, reduced wheal size by 32% at the same period. The ability of temelastine to antagonize the histamine-induced skin reaction over 20 hr was evaluated in a second randomized, double-blind study. Eight subjects participated. Temelastine, 100 mg, produced reductions of 64, 49, 56 and 51% in histamine wheal area at 8, 12, 16 and 20 hr, respectively. Plasma concentrations at these times were 4.04, 2.77, 1.88, and 1.44 μmol/l, respectively. These data suggest that blood levels as low as 1.44 μmol/l may be sufficient to produce an antihistaminic effect, and that daily or twice daily dosing with 100 mg may be adequate to control allergic symptoms.

scholarly journals Pharmacokinetic Profiles of Gabapentin after Oral and Subcutaneous Administration in Black-tailed Prairie Dogs (Cynomys ludovicianus)

2020 ◽  
Vol 59 (3) ◽  
pp. 305-309
Author(s):  
Patrick O Mills ◽  
Cassandra O Tansey ◽  
Sarah C Genzer ◽  
Matthew R Mauldin ◽  
Rex A Howard ◽  
...  
Keyword(s):  
Peak Plasma ◽  
Plasma Concentrations ◽  
Subcutaneous Administration ◽  
Effective Concentration ◽  
Cynomys Ludovicianus ◽  
Prairie Dogs ◽  
Noncompartmental Analysis ◽  
Chronic Neuropathic Pain ◽  
Half Maximal Effective Concentration ◽  
Oral Doses

In veterinary and human medicine, gabapentin (a chemical analog of γ-aminobutyric acid) is commonly prescribed to treat postoperative and chronic neuropathic pain. This study explored the pharmacokinetics of oral and subcutaneous administration of gabapentin at high (80 mg/kg) and low (30 mg/kg) doses as a potential analgesic in black-tailed prairie dogs (Cynomys ludovicianus; n = 24). The doses (30 and 80 mg/kg) and half maximal effective concentration (1.4 to 16.7 ng/mL) for this study were extrapolated from pharmacokinetic efficacy studies in rats, rabbits, and cats. Gabapentin in plasma was measured by using an immunoassay, and data were evaluated using noncompartmental analysis. The peak plasma concentrations (mean ±1 SD) were 42.6 ±14.8 and 115.5 ±15.2 ng/mL, respectively, after 30 and 80 mg/kg SC and 14.5 ±3.5 and 20.7 ±6.1 ng/mL after the low and high oral dosages, respectively. All peak plasma concentrations of gabapentin occurred within 5 h of administration. Disappearance half-lives for the low and high oral doses were 7.4 ± 6.0 h and 5.0 ± 0.8 h, respectively. The results of this study demonstrate that oral administration of gabapentin at low (30 mg/kg) doses likely would achieve and maintain plasma concentrations at half maximum effective concentration for 12 h, making it a viable option for an every 12-h treatment.

Effects of Two Different Doses of Hirudin on APTT, Determined with Eight Different Reagents

1995 ◽  
Vol 73 (02) ◽  
pp. 219-222 ◽  
Author(s):  
Manuel Monreal ◽  
Luis Monreal ◽  
Rafael Ruiz de Gopegui ◽  
Yvonne Espada ◽  
Ana Maria Angles ◽  
...  
Keyword(s):  
Ex Vivo ◽  
Anticoagulant Activity ◽  
Subcutaneous Administration ◽  
In Vitro Study ◽  
Ex Vivo Model ◽  
Suitable Candidate ◽  
Significant Prolongation ◽  
High Doses ◽  
Different Doses

SummaryThe APTT has been considered the most suitable candidate to monitor the anticoagulant activity of hirudin. However, its use is hampered by problems of standardization, which make the results heavily dependent on the responsiveness of the reagent used. Our aim was to investigate if this different responsiveness of different reagents when added in vitro is to be confirmed in an ex vivo study.Two different doses of r-hirudin (CGP 39393), 0.3 mg/kg and 1 mg/kg, were administered subcutaneously to 20 New Zealand male rabbits, and the differences in prolongation of APTT 2 and 12 h later were compared, using 8 widely used commercial reagents. All groups exhibited a significant prolongation of APTT 2 h after sc administration of hirudin, both at low and high doses. But this prolongation persisted 12 h later only when the PTTa reagent (Boehringer Mannheim) was used. In general, hirudin prolonged the APTT most with the silica- based reagents.In a further study, we compared the same APTT reagents in an in vitro study in which normal pooled plasma was mixed with increasing amount of hirudin. We failed to confirm a higher sensitivity for silica- containing reagents. Thus, we conclude that subcutaneous administration of hirudin prolongs the APTT most with the silica-based reagents, but this effect is exclusive for the ex vivo model.

Modeling Studies of the Dynamic Control of Hepatic Glucose Balance

1975 ◽  
Vol 97 (3) ◽  
pp. 266-275
Author(s):  
R. N. Bergman ◽  
M. El Refai
Keyword(s):  
Central Nervous System ◽  
Dynamic Control ◽  
Plasma Concentrations ◽  
Glycogen Metabolism ◽  
Hepatic Glycogen ◽  
Simulation Studies ◽  
Biochemical Effects ◽  
Hepatic Glucose ◽  
Large Fluctuations ◽  
The Central Nervous System

The survival of mammals is dependent upon a relatively constant, adequate supply of glucose to the central nervous system, despite large fluctuations in the amount of food available. When food is abundant, the liver stores ingested carbohydrate as glycogen, and during fasts, the stored glycogen is released at a precisely regulated rate to maintain the blood glucose level. The rates of storage and release of carbohydrate by the liver are determined by the plasma concentrations of several bloodborne signals; most important are the concentrations of glucose, and the hormones insulin and glucagon. To understand the complex control relationships of these three signals as they affect the liver, their individual dynamic influences have been determined experimentally, and they have been integrated by means of a computer simulation of the pathways of hepatic glycogen metabolism. The simulation studies have led to specific hypotheses about the biochemical effects of glucose and insulin on the liver. The simulation studies have also led to the conclusion that glucose exerts a rapid moment-to-moment influence of glucose on the rate of uptake of glucose by the liver. Insulin, however, by exerting a slower influence on the sensitivity of the liver to glucose, is very effective in “optimizing” the amount of glycogen which the liver stores food during food intake. Thus, integrated experimental and simulation studies can lead to a view of a physiological regulating system which does not emerge from either approach used alone.

scholarly journals Vitamin C—Sources, Physiological Role, Kinetics, Deficiency, Use, Toxicity, and Determination

Nutrients ◽  
2021 ◽  
Vol 13 (2) ◽  
pp. 615
Author(s):  
Martin Doseděl ◽  
Eduard Jirkovský ◽  
Kateřina Macáková ◽  
Lenka Krčmová ◽  
Lenka Javorská ◽  
...  
Keyword(s):  
Ascorbic Acid ◽  
Vitamin C ◽  
Iron Absorption ◽  
Plasma Concentrations ◽  
Physiological Role ◽  
Renal Stones ◽  
Anti Oxidant ◽  
High Doses ◽  
Epigenetic Processes

Vitamin C (L-ascorbic acid) has been known as an antioxidant for most people. However, its physiological role is much larger and encompasses very different processes ranging from facilitation of iron absorption through involvement in hormones and carnitine synthesis for important roles in epigenetic processes. Contrarily, high doses act as a pro-oxidant than an anti-oxidant. This may also be the reason why plasma levels are meticulously regulated on the level of absorption and excretion in the kidney. Interestingly, most cells contain vitamin C in millimolar concentrations, which is much higher than its plasma concentrations, and compared to other vitamins. The role of vitamin C is well demonstrated by miscellaneous symptoms of its absence—scurvy. The only clinically well-documented indication for vitamin C is scurvy. The effects of vitamin C administration on cancer, cardiovascular diseases, and infections are rather minor or even debatable in the general population. Vitamin C is relatively safe, but caution should be given to the administration of high doses, which can cause overt side effects in some susceptible patients (e.g., oxalate renal stones). Lastly, analytical methods for its determination with advantages and pitfalls are also discussed in this review.

Some Aspects of the Psychopharmacological Activity of Maprotiline (Ludiomil®): Effects of Single and Repeated Treatments

1978 ◽  
Vol 6 (6) ◽  
pp. 421-429 ◽  
Author(s):  
A Delini-Stula ◽  
E Radeke ◽  
A Vassout
Keyword(s):  
Nervous System ◽  
Chronic Treatment ◽  
Conditioned Fear ◽  
Conditioned Avoidance ◽  
Repeated Treatment ◽  
Antidepressant Effects ◽  
The Central Nervous System ◽  
Pre Treatment ◽  
High Doses ◽  
Psychopharmacological Activity

Three different aspects of the psychopharmacological activity of the antidepressant maprotiline were investigated: its influence on serotoninergic functions the effects produced by chronic treatment its central nervous depressant and anxiolytic properties. Study of the effects of maprotiline on 5-HTP-induced head-twitch in mice pre-treated with pargyline or on hyperpyrexia in rats provided no evidence that the drug interferes with serotonin-mediated functions in the central nervous system even after quite high doses. These findings corroborate the results of extensive neurobiochemical investigations, which failed to demonstrate any influence of maprotiline on the metabolism of serotonin. Chronic studies showed that classical effects of maprotiline such as antagonism against reserpine-induced ptosis or tetrabenazine-induced catalepsy do not change in their intensity after daily administration of the drugs in a dose of 30 mg/kg p.o.for 11 days. A new component of the action of the compound, not detectable after one single dose, seems to appear, however, after repeated treatment (8 days). This effect is manifested in the restoration of conditioned avoidance behaviour after its suppression by pre-treatment with reserpine. The same effect is produced by imipramine. It is suggested that this restorative effect may be due to an additional activation of the dopaminergic nervous system and may have a bearing on the appearance of clinical antidepressant effects. Maprotiline was found to potentiate central nervous depressant effects of drugs like chlorpromazine, phenobarbitone and propranolol. This affords further confirmation that, in addition to its antidepressant qualities, it possesses sedative actions. An anxiolytic component was also demonstrated in rats in which maprotiline suppressed the conditioned, fear-induced rise in body-temperature.

Modification of Insulin Resistance

1956 ◽  
Vol 102 (428) ◽  
pp. 576-588 ◽  
Author(s):  
Edward Marley
Keyword(s):  
Deep Coma ◽  
Insulin Dosage ◽  
Insulin Resistant ◽  
Significant Difference ◽  
High Insulin ◽  
Insulin Coma ◽  
The Central Nervous System ◽  
Resistance To Insulin ◽  
High Doses ◽  
Special Instance

Sakel (1938a) drew attention to the difficulty of establishing satisfactory comas in a minority of patients attending for Deep Insulin therapy. This phenomenon has since been confirmed by other workers including Tillim (1938) whose patient received 500 units of insulin without the production of deep coma, by Hall (1940) who reported an instance in which 1,000 units of insulin was equally unsuccessful, by Reznikoff and Scott (1942) who described how neither 120 nor 1,000 units of insulin when injected intravenously produced any significant difference in hypoglycaemia in insulin resistant patients, and more recently by Fogarty (1953) whose case required 5,000 units of insulin for the production even of sopor. Other recorded examples of resistance to massive doses of insulin include those of Bantinget al.(1938) and Tennent (1944).Various explanations of this perverse response to insulin have been formulated, including that of Jones (1939) who proposed that resistance to insulin was both a problem of true insulin insensitivity and also of an anomalous response of the central nervous system to hypoglycaemia. Medunaet al.(1942) preferred to ascribe it to anti-insulin factors in the blood, but a more interesting interpretation derived from Freudenberg (1952) who suggested that if the effects of high insulin dosage employed in insulin coma treatment were regarded as a special instance of a stress response, then the fluctuations and differences in response could be equated in terms of the General Adaptation Syndrome of Selye. High doses were thus an index of an effective “alarm stage” characterized by a discharge from plentiful adrenocortical reserves.

scholarly journals Activity of Amoxicillin-Clavulanate against Penicillin-Resistant Streptococcus pneumoniae in an Experimental Respiratory Infection Model in Rats

1998 ◽  
Vol 42 (4) ◽  
pp. 813-817 ◽  
Author(s):  
Gillian M. Smith ◽  
Brian Slocombe ◽  
Karen H. Abbott ◽  
Linda W. Mizen
Keyword(s):  
Streptococcus Pneumoniae ◽  
Infection Model ◽  
Time Curve ◽  
Penicillin Binding Proteins ◽  
Amoxicillin Clavulanate ◽  
Potassium Clavulanate ◽  
Differential Binding ◽  
High Doses ◽  
Oral Doses

ABSTRACT High doses of amoxicillin, equivalent to those produced by 500- and 750-mg oral doses in humans (area under the plasma concentration-time curve), were effective against a penicillin-resistant strain ofStreptococcus pneumoniae in an experimental respiratory tract infection in immunocompromised rats; this superior activity confirms the results of previous studies. An unexpected enhancement of amoxicillin’s antibacterial activity in vivo against penicillin-resistant and -susceptible S. pneumoniaestrains was observed when subtherapeutic doses of amoxicillin were coadministered with the β-lactamase inhibitor potassium clavulanate. The reason for this enhancement was unclear since these organisms do not produce β-lactamase. The differential binding of clavulanic acid and amoxicillin to penicillin-binding proteins may have contributed to the observed effects.

scholarly journals Plasma and tissue clindamycin antimicrobial activity after parenteral administration to cats under surgical conditions

2017 ◽  
Vol 7 (1) ◽  
Author(s):  
Sabrina Passini ◽  
Laura Montoya ◽  
Martín Lupi ◽  
Paula Lorenzini ◽  
María Fabiana Landoni ◽  
...  
Keyword(s):  
Peak Plasma ◽  
Subcutaneous Tissue ◽  
Plasma Concentrations ◽  
Subcutaneous Administration ◽  
Dose Interval ◽  
Tissue Concentrations ◽  
Administration Routes ◽  
Infection Treatment ◽  
Plasma Concentration Ratio ◽  
Surgical Conditions

Clindamycin plasma and tissue disposition in cats under surgical conditions after a single intravenous (IV), intramuscular (IM) and subcutaneous (SC) administration at a dose rate of 10 mg/kg were studied. After intravenous, intramuscular and subcutaneous administration, peak plasma concentrations were 10.93±3.78 μg/mL (Cp(0)), 5.93±1.18 μg/mL (Cmax)) and 6.30±0.88 μg/mL (Cmax)), respectively. Eight hours after clindamycin IV, IM and SC administration plasma concentrations declined to 2.01±0.61 μg/mL, 2.96±0.43 μg/mL and 3.36±0.97 μg/mL, respectively. Sixty to 90 minutes after clindamycin administration, tissue concentrations ranged from a minimum in subcutaneous tissue of 4.90 μg/g (IV), 3.06 μg/g (IM) and, 3.13 μg/g (SC) to a maximum in uterus of 13.41 μg/g (IV), 14.07 μg/g (IM) and, 14.44 μg/g (SC). The lowest tissue/plasma concentration ratio for the three administration routes was observed in subcutaneous tissue, while the highest was observed at genital level (ovary for IV and IM and uterus for SC). Estimated efficacy predictor (AUC/MIC), considering MIC breakpoint for bacteria isolated from animals, indicates that clindamycin administered IV, IM or SC at the studied dose is appropriated for perioperative prophylactic protocols and that given with a dose interval of 12 hours would be effective for susceptible infection treatment in cats.

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