Fluorescent diethylcarbamazine analogues: sites of accumulation in Brugia malayi.

New fluorescein and rhodamine B-labeled antifilarial drug DEC analogues for use in drug localization studies with confocal microscopy have been prepared by a high-yield three-step synthesis. The resulting beta-amine-substituted DEC analogue has a single ethyl substituent which is beta-aminated to accommodate the fluorophore of either fluorescein isothiocyananate or rhodamine B. Confocal microscopy is used to show that the drug accumulates in the adult filarial worms in the pharynx, esophagus, and near the nerve ring of all adults, as well as in the uteri and vulva and the testes of the females and males.

Comparative antifilarial efficacy of the N-oxides of diethylcarbamazine and two of its analogues.

The N-oxides of 1-diethyl carbamoyl-4-methyl piperazine (DEC), 3-ethyl-8-methyl, 1,3,8-triazabicyclo (4,4,0) decan-2-one (centperazine) and 1-methyl-4-(pyrrolidin-1-yl-carbonyl) piperazine (CDRI Comp. 72/70) have been evaluated against Limotosoides carinii infection in cotton rats to establish whether conversion of the three antifilarials into N-oxides would lead to exertion of better antifilarial activity. Of the three N-oxides, N-oxide of DEC showed significantly more suppressive effect on circulating microfilariae in comparison to its parent compound. However, adult worms were unaffected. It was observed that basicity of the N-CH3 group did not play major role in exertion of activity of DEC and related compounds. Nevertheless, two other N-oxides were inactive.

Pharmacological analysis of the neuromuscular properties of diethylcarbamazine citrate in vitro.

The actions of diethylcarbamazine citrate (DECC) have been examined on agonist- and electrically-induced contractures and twitches of the isolated chick biventer cervicis and rat phrenic nerve-hemidiaphragm muscle preparations in order to analyse the effects of this commonly-prescribed anthelmintic drug at the neuromuscular junction. DECC (5 x 10(-1)-1.5 mM) produced a concentration-dependent initial augmentation of the indirect electrically-evoked twitches followed by a sustained, longer-lasting secondary depression of the twitches of all the skeletal muscle-nerve preparations examined. The DECC-induced twitch depression was competitively reversed by increasing the bathing fluid calcium ion concentration (Ca2+). DECC (10(-3)-2.5 x 10(-2) M) caused marked augmentation of the contractural responses of innervated chick biventer muscle preparations induced by bath-applied low concentrations of carbachol, acetylcholine or nicotine, and depressed those contractural responses of the muscle elicited by hgh concentrations of the agonists. On their own accord, high concentrations of DECC (10(-1)-2.5 mM) dose-dependently contracted isolated chick biventer cervicis muscle preparations, and demonstrated measurable anticholinesterase activity. It is concluded that DECC has both direct (post-junctional) and indirect (pre-junctional) effects at the neuromuscular junction, and that the neuromuscular blockade produced by this anthelmintic agent is probably post-junctional in origin.

Long-term treatment of onchocerciasis patients from the Liberian rain-forest with low doses of diethylcarbamazine citrate after complete nodulectomy.

60 completely nodulectomized volunteers from the Liberian rain-forest were given an initial treatment with diethylcarbamazine citrate (DEC-C) for one week with gradually increasing doses up to a total of 1.1 g per patient. A long-term treatment followed with 50 mg DEC-C per week for 12 months. Immediately after the initial treatment the mean microfilarial density decreased to 4% to 6% of the pre-treatment level. After one year the microfilarial density had again increased to 12% to 29% of the pre-treatment level. Although the intake of the weekly 50 mg DEC-C was in no case regular, the microfilarial densities could be kept at a low level throughout the trial. However, even with the combined treatment--preceding nodulectomy and long-term trial with DEC-C--it was not possible to get the patients free from microfilariae.

Effects of serum from treated patients on antibody-dependent cell adherence to the infective larvae of Brugia malayi.

Adherence assays were used to demonstrate the in vitro effect of serum-dependent cellular adherence of human buffy coat cells to infective larvae of Brugia malayi in filariasis patients treated with antifilarial drugs. In this study, microfilaraemic patients were treated with either diethylcarbamazine citrate (DEC), mebendazole or levamisole hydrochloride. It was found that DEC and mebendazole decreased the motility of infective larvae due to a direct action of the drugs. Sera of levamisole-treated patients caused increased adherence of human buffy coat cells to infective larvae, leading to a decrease in motility and cuticular damage as confirmed by scanning electron microscopic studies. However, serum of levamisole-treated patients alone could cause a similar lethal effect on infective larvae. Studies with the indirect fluorescent antibody test suggested that IgM was involved in this phenomenon. Complement did not appear to be important.

Efficacy of oral and transepidermal application of diethylcarbamazine citrate in Brugia malayi infected cats.

This experimental study showed that daily oral administration of DEC at levels of 5 to 15 mg/kg/day with food for 3 weeks decreased the level of both developing and adult B. malayi in infected cats. There were no adverse reactions due to the medication. Topical application of 5% DEC in skin cream or in mineral oil appears to be effective in killing developing B. malayi in cats.

Effect of diethylcarbamazine citrate on Brugia malayi infections in cats following daily, weekly, or monthly administration.

Cats with patent infections of Brugia malayi were treated by intraperitoneal injection of diethylcarbamazine citrate (DEC) for 6 consecutive days, weekly for 6 consecutive weeks or monthly for 3 months. Each cat received a total of 100 mg DEC per kg. At necropsy 7 months after infection, no living worms were recovered from any of eight cats treated weekly and only one of nine cats treated daily had a single living Brugia. Five of nine cats treated monthly and six of eight untreated controls had one or more living worms. Cats treated weekly showed a larger decline in microfilariae than those of the other treated groups. The mean microfilariae level of untreated controls increased 2-fold. At necropsy, gross appearance of regional lymphatics in daily and weekly treated cats resembled those of uninfected controls more closely than those in cats treated monthly or untreated. Differences in degree of histological changes between groups of infected cats were not apparent. Weekly administration of DEC appeared to be the most effective regimen; monthly treatment was less effective.

The effects of diethylcarbamazine citrate, antihistamines and corticosteroid derivatives on skin reactivity to Onchocerca supernatants.

A single dose of promethazine or of betamethazone, either alone or compounded with dexchloropheniramine, was found to inhibit skin wheal formation in onchocerciasis patients challenged with Onchocerca supernatants. The mean wheal diameter developing 24 hours after drug administration ranged between 40-60% less than the original pre-treatment diameter but this effect had been abolished or was significantly less by 48 hours. Diethycarbamazinecitrate had only a 20% inhibitory effect on the wheal diameter of the skin reaction. It is concluded that antihistamines and corticosteroid derivates may interfere with the immunodiagnostic skin test for onchocerciasis based on skin reactivity to Onchocerca supernatants, unless measures are taken to ensure that these drugs are not consumed within the 48 hours preceding the skin test.

Myocardial depressant effects of diethylcarbamazine citrate in vitro.

The effects of diethylcarbamazine citrate (DECC) have been examined in isolated, electrically driven left atria of guinea-pigs. This anthelmintic drug (DECC, 10(-9) -10(-4) M) produced a sustained, concentration-dependent depression of atrial contractile tension that was reversible by replacing the incubation fluid with DECC-free physiological solution. The negative inotropic response induced by DECC was antagonized in a competitive manner by increasing the calcium ion (Ca2+) concentration of the bathing fluid. On the contrary, the myocardial depressant effects of DECC were antagonized in a non-competitive manner by noradrenaline (NA). The present findings suggest a direct negative inotropic effect of DECC and indicate that this anthelmintic drug interferes with the empirical function of Ca2+ in the events leading to mechanical activity of the isolated atrial myocardium.

Studies on the chemoprophylaxis of subperiodic Brugia malayi infection in the leaf monkey (Presbytis melalophos) with diethylcarbamazine citrate.

The chemoprophylactic use of diethylcarbamazine citrate at total oral doses of 15--180 mg/kg body weight was tested against subperiodic Brugia malayi infection in the leaf monkey (Presbytis melalophos). A total dose of 45 mg/kg body weight given over 9 days killed all developing infective larvae. Similarly, a total dose of 35 mg/kg body weight given over 7 days killed all fourth stage larvae. The minimum effective dose that prevents infection would be 5 mg/kg body weight daily for 7 days every month.

Aqueous humor and serum IgE antibody in experimental ocular Onchocerca infection of guinea pigs.

Infection of inbred Strain 2 guinea pigs by subcutaneous or intradermal injection of fresh or cryopreserved living Onchocerca lienalis microfilariae, followed by a challenge intracorneal infection of microfilariae, resulted in serum and aqueous IgE antibody and in significant corneal inflammation. Systemic or intraocular infections given separately were not sufficient to elicit IgE antibody or ocular inflammation. When intravenous transfer of pooled spleen cell suspensions from systemically infected donors to normal syngeneic recipients was substituted for the course of systemic infections, a subsequent intracorneal challenge of cell transfer recipients with microfilariae produced serum and aqueous IgE antibody. Administration of diethylcarbamazine citrate to infected animals following the intracorneal challenge resulted in increased serum IgE antibody and in increased corneal inflammation.

Equine immunology 3: immunopharmacology--anti-inflammatory and antihypersensitivity drugs.

This article reviews anti-inflammatory and antihypersensitivity drugs under these 4 headings: Functional or physiological antagonists; Selective pharmacological inhibitors; Broad spectrum anti-inflammatory drugs; Miscellaneous inhibitors. The compounds considered include sympathomimetic amines, anticholinergic drugs, antihistamine drugs, tryptamine antagonists and dopamine antagonists, glucocorticosteroids and non-steroidal anti-inflammatory drugs, disodium cromoglycate and diethylcarbamazine citrate. The relationship of the pharmacological actions of these compounds is considered in the context of clinical conditions. The potential for immunomodulatory pharmacology is discussed using levamisole as an example.