Piperazine, a six membered nitrogen containing heterocycle, is of great significance to the rational design of drugs. This moiety can be found in a plethora of well-known drugs with various therapeutic uses, such as antipsychotic, antihistamine, antianginal, antidepressant, anticancer, antiviral, cardio protectors, anti-inflammatory, and imaging agents. Slight modification to the substitution pattern on the piperazine nucleus facilitates a recognizable difference in the medicinal potential of the resultant molecules. Piperazine has been used as an antihelmintic drug. Piperazine works by paralyzing the worms. They are then passed in the stool.

The discovery of pamaquine, developed by replacing one of the methyl groups of methylene blue by a dialkylaminoalkyl chain, was a landmark in the design of drugs for malaria. It is closely related to primaquine. The administration of pamaquine during the incubation period delayed but did not prevent primary attacks of a New Guinea strain of Plasmodium vivax malaria. Hemolytic anemia after administration of the antimalarial drug pamaquine was reported in patients with Glucose-6-phosphate dehydrogenase (G6PD) deficiency. Pamaquine itself could not be used clinically due to high toxicity.

Cinchonine is cinchona bark alkaloid, which was used to treat malaria. Cinchonine is more efficient than quinine in increasing the intracellular accumulation and restoring the cytotoxicity of doxorubicin, mitoxantrone and vincristine on well-characterized multidrug resistance (MDR) cell lines. In the phase I of clinical trial was investigated the properties of cinchonine combined with the CHVP (cyclophosphamide, doxorubicin, vinblastine, methylprednisolone) regimen in relapsed and refractory lymphoproliferative syndromes.

Stibophen (Fuadin), an organic trivalent antimony compound, has been used for many years in the treatment of schistosomiasis. Stibophen is used as treatment of schistosomiasis by intramuscular injection. Stibophen is known to act by selectively inhibiting worm PFK.

Ammonium dihydrogen arsenate is an inorganic compound that has been considered a potential electro-optic material and has been explored by a number of investigators for modulation purposes. Ammonium arsenate is a cancerogenic substance.

Cinchonine is cinchona bark alkaloid, which was used to treat malaria. Cinchonine is more efficient than quinine in increasing the intracellular accumulation and restoring the cytotoxicity of doxorubicin, mitoxantrone and vincristine on well-characterized multidrug resistance (MDR) cell lines. In the phase I of clinical trial was investigated the properties of cinchonine combined with the CHVP (cyclophosphamide, doxorubicin, vinblastine, methylprednisolone) regimen in relapsed and refractory lymphoproliferative syndromes.

Emetine is a principal alkaloid of ipecac, isolated from the ground roots of Uragoga ipecacuanha. Early use of emetine was in the form of oral administration of the extract of ipecac root, or ipecacuanha. This extract contains several, including cephaeline, and others. The identification of emetine as a more potent agent improved the treatment of amoebiasis. While the use of emetine still caused nausea, it was more effective than the crude extract of ipecac root. Additionally, emetine could be administered hypodermically which still produced nausea, but not to the degree experienced in oral administration. Emetine dihydrochloride hydrate is used in the laboratory to block protein synthesis in eukaryotic cells. It does this by binding to the 40S subunit of the ribosome. Emetine induces hypotension by blocking adrenoreceptors. Also, emetine was identified as a specific inhibitor of HIF-2α protein stability and transcriptional activity. Heavy or over usage of emetine can carry the risk of developing proximal myopathy and/or cardiomyopathy.

Dymanthine (Thelmesan) is an Anthelmintic, it is prepared as the hydrochloride and has some activity against hookworm infection, ascariasis, trichuriasis and hymenolepiasis. The drug appears to be safe, well tolerated and to cause few side effects (nausea, vomiting, headache, diarrhea, giddiness).

Monensin is an antibiotic produced as a byproduct of fermentation by Streptomyces cinnamonensis and belongs to a family of drugs known as polyether antibiotics or ionophores. The drug was approved by FDA for the prevention of coccidiosis in turkeys, chickens, quail, cattle, goats, calves (Coban, Rumensin). The exact mechanism of monesin action is unknown, however there are several hypotesis, which includes the inhibition of K+ transport, the inhibition of the transport of carbohydrates across the host cell membrane, the interruption host cell invasion by sporozoites, etc.

Morantel (1,4,5,6-tetrahydro-1-methyl-2-[2-(3-methyl-2-thienyl)ethenyl pyrimidine) is a tetrahydro-pyrimidine anthelmintic, differing from the related analogue pyrantel by the presence of a methyl group on the thiophene ring. Morantel tartrate, manufactured by Pfizer, Inc., was approved in the United States for use in cattle in 1981, and entered the market in early 1982. Three formulations have been approved in the United States: RUMATEL® Medicated Premix-88; RUMATEL Cattle Wormer Bolus, and PARATECT FLEX™ Diffuser, a sustained release bolus. It is intended to treat roundworms and tapeworms. Morantel is administered in lactating and non lactating cattle as morantel tartrate as a slow-release bolus (11.8 g morantel base per animal) or as a single oral dose of 6 to 7.5 mg morantel base/kg bw and in pigs at a single dose equivalent to 7.5 mg base/kg bw. In sheep, the citrate salt is administered at a single dose equivalent to 5 to 6 mg morantel base/kg bw. Morantel acts as a potent agonist at the acetylcholine receptors on the muscle cells of nematodes. Activation of the acetylcholine receptors induces a prolonged, spastic paralysis of the worms and expulsion from the host. It also been reported to block neurotransmission in vertebrates, to possess nicotine-like properties and to mimic acetylcholine at receptors in autonomic ganglia, adrenal medullae and respiratory tissues. Morantel and its salts are not used in human medicines.