Praziquantel, marketed as Biltricide, is an anthelmintic used in humans and animals for the treatment of tapeworms and flukes. Specifically, it is effective against schistosoma, Clonorchis sinensis the fish tape worm Diphyllobothrium latum. Praziquantel works by causing severe spasms and paralysis of the worms' muscles. This paralysis is accompanied - and probably caused - by a rapid Ca 2+ influx inside the schistosome. Morphological alterations are another early effect of praziquantel. These morphological alterations are accompanied by an increased exposure of schistosome antigens at the parasite surface. The worms are then either completely destroyed in the intestine or passed in the stool. An interesting quirk of praziquantel is that it is relatively ineffective against juvenile schistosomes. While initially effective, effectiveness against schistosomes decreases until it reaches a minimum at 3-4 weeks. Effectiveness then increases again until it is once again fully effective at 6-7 weeks. Glutathione S-transferase (GST), an essential detoxification enzyme in parasitic helminths, is a major vaccine target and a drug target against schistosomiasis. Schistosome calcium ion channels are currently the only known target of praziquantel. The antibiotic rifampicin decreases plasma concentrations of praziquantel. Carbamazepine and phenytoin are reported to reduce the bioavailability of praziquantel. Chloroquine reduces the bioavailability of praziquantel. The drug cimetidine heightens praziquantel bioavailability.

Mebendazole, known as Emverm is a (synthetic) broad-spectrum anthelmintic that acts by interfering with carbohydrate metabolism and inhibiting polymerization of microtubules. The loss of the cytoplasmic microtubules leads to impaired uptake of glucose by the larval and adult stages of the susceptible parasites, and depletes their glycogen stores. Degenerative changes in the endoplasmic reticulum, the mitochondria of the germinal layer, and the subsequent release of lysosomes result in decreased production of adenosine triphosphate (ATP), which is the energy required for the survival of the helminth. Due to diminished energy production, the parasite is immobilized and eventually dies. Emverm tablets are used for the treatment of Enterobius vermicularis (pinworm), Trichuris trichiura (whipworm), Ascaris lumbricoides (common roundworm), Ancylostoma duodenale (common hookworm), Necator americanus (American hookworm) in single or mixed infections. All metabolites are devoid of anthelmintic activity. In man, approximately 2% of administered mebendazole is excreted in urine and the remainder in the feces as unchanged drug or a primary metabolite. Preliminary evidence suggests that cimetidine inhibits mebendazole metabolism and may result in an increase in plasma concentrations drug. Mebendazole sometimes causes diarrhea, abdominal pain, and elevated liver enzymes. In rare cases, it has been associated with a dangerously low white blood cell count, low platelet count, and hair loss, with a risk of agranulocytosis in rare cases

Pyrantel is an anthelmintic, which acts as an agonist of nicotinic receptors (AChRs) of nematodes and exerts its therapeutic effects by depolarizing their muscle membranes. It is used to treat a number of parasitic worm infections. This includes ascariasis, hookworm infections, enterobiasis (pinworm infection), trichostrongyliasis and trichinellosis. Common adverse reactions include diarrhea, nausea, vomiting, dizziness, headache and somnolence.

Dexamisole is the dextro-isomer of tetramisole, a broad spectrum anthelmintic. Dexamisole significantly improves mood and psychotonicity. In adrenergically innervated blood vessels dexamisole inhibits neuronal uptake of norepinephrine more than levamisole. Dexamisole antagonized the reserpine-induced hypothermia but was ineffective in the apomorphine-induced hypothermia in mice. It reduced ptosis produced by reserpine in mice but this effect was very weak. The effect of dexamisole on the amphetamine-induced hyperactivity depended upon the animal species. Dexamisole reduced the duration of immobility in the despair test in rats. It did not modify the 5-HTP-induced head twitch reaction in mice but produced stimulation of the hind limb flexor reflex in spinal rats. The latter effect was blocked by phenoxybenzamine but not by cyproheptadine and metergoline. Dexamisole also exerted a sedative and hypothermic effect. The above findings indicate that the pharmacological profile of dexamisole resembles in some respects that of tricyclic antidepressants; they also point out that this drug has a central noradrenergic activity.

Niclosamide is an antihelminth used against tapeworm infections. It may act by the uncoupling of the electron transport chain to ATP synthase. The disturbance of this crucial metabolic pathway prevents creation of adenosine tri-phosphate (ATP), an essential molecule that supplies energy for metabolism. Niclosamide works by killing tapeworms on contact. Adult worms (but not ova) are rapidly killed, presumably due to uncoupling of oxidative phosphorylation or stimulation of ATPase activity. The killed worms are then passed in the stool or sometimes destroyed in the intestine. Niclosamide may work as a molluscicide by binding to and damaging DNA. Niclosamide is used for the treatment of tapeworm and intestinal fluke infections: Taenia saginata (Beef Tapeworm), Taenia solium (Pork Tapeworm), Diphyllobothrium latum (Fish Tapeworm), Fasciolopsis buski (large intestinal fluke). Niclosamide is also used as a molluscicide in the control of schistosomiasis. Niclosamide was marketed under the trade name Niclocide, now discontinued.

Tetramisole is a racemic mixture of levamisole and its enantiomer dexamisole, which is a specific inhibitor of tissue non-specific alkaline phosphatase (TNAP). This drug is used in veterinary to treat of ascariasis and other worm infections e.g hook-"ms. And also is used as an immunostimulant (in that case it is used for longer periods of time).

Famphur is an insecticide and antihelmenthic. Famphur is approved in cattle as a pour-on (NADA 34-697; 21 CFR 524.900) and as medicated feed (NADA 34-266; 21 CFR 558.254). It is a component of the FDA-approved TRAMISOL X-TRA Combination Paste, used for the treatment of cattle infected with the following parasites: Stomach worms (Haemonchus, Trichostrongylus, Ostertagia), intestinal worms (Trichostrongylus, Cooperia, Nematodirus, Bunostomum, Oesophagostomum), lungworms (Dictyocaulus), cattle grubs (Hypoderma), biting lice (Bovicola), and sucking lice (Linognathus, Solenoptes). Famphur is a cholinesterase-inhibiting drug.

Dexamisole is the dextro-isomer of tetramisole, a broad spectrum anthelmintic. Dexamisole significantly improves mood and psychotonicity. In adrenergically innervated blood vessels dexamisole inhibits neuronal uptake of norepinephrine more than levamisole. Dexamisole antagonized the reserpine-induced hypothermia but was ineffective in the apomorphine-induced hypothermia in mice. It reduced ptosis produced by reserpine in mice but this effect was very weak. The effect of dexamisole on the amphetamine-induced hyperactivity depended upon the animal species. Dexamisole reduced the duration of immobility in the despair test in rats. It did not modify the 5-HTP-induced head twitch reaction in mice but produced stimulation of the hind limb flexor reflex in spinal rats. The latter effect was blocked by phenoxybenzamine but not by cyproheptadine and metergoline. Dexamisole also exerted a sedative and hypothermic effect. The above findings indicate that the pharmacological profile of dexamisole resembles in some respects that of tricyclic antidepressants; they also point out that this drug has a central noradrenergic activity.

Levamisole (the trade name Ergamisol), an anthelminthic drug with immunological properties. It also has antitumor activity when administered with 5-fluorouracil in patients with Duke's C colorectal carcinoma; however, this use was discontinued. The mechanism of the antitumor effect is unknown but has been postulated to be related to levamisole's immunomodulatory properties. Levamisole can stimulate antibody formation to various antigens, enhance T-cell responses by stimulating T-cell activation and proliferation, potentiate monocyte and macrophage functions including phagocytosis, chemotaxis and increases motility, adherence, and chemotaxis. Levamisole inhibits alkaline phosphatase and possesses cholinergic activity. The mechanism of action of levamisole as an antiparasitic agent, for example, to treat ascariasis, relates to its agonistic activity to L-subtype nicotinic acetylcholine receptors in nematode muscles. In addition, levamisole was studied for preventing relapses of the steroid-sensitive idiopathic nephrotic syndrome (SSINS). It was shown, that alone or in combination with steroids, the drug can prolong the time to relapse and prevented recurrence during one year of treatment. However, these studies also were also discontinued.

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.