Praziquantel Therapy

Praziquantel is a pharmacological active substance that is used for the therapy of parasite infestation. The active ingredient was developed in the 1970s and has been the drug of choice for worm diseases ever since.

What is Praziquantel Therapy?

Praziquantel is a so-called antihelminthic, anti-worm agent. As such, it is used with success in infestations with flukes, flatworms, tapeworms and leeches. Since its development, the agent has quickly established itself not only in human medicine, but also in veterinary medicine.

The active ingredient was developed in the 1970s in cooperation between the two major pharmaceutical groups Bayer and Merck. After a lead time of over ten years, Praziquantel came onto the market in the early 1980s. Chemically speaking, praziquantel is a quinoline derivative.

It works locally on the mucous membranes and also has a systemic effect. It is therefore well suited for oral therapy in humans and animals in the event of parasite infestation. The duration of intake and type of application always depend on the degree and type of parasite infestation. The active ingredient is effective against a large number of parasites in humans and animals. Often only a single dose is required to kill all parasites in the gastrointestinal tract quickly and reliably.

Function, effect & goals

In veterinary medicine, praziquantel is used prophylactically as a wormer treatment for dogs and cats. If a parasite infestation is already present, these will be killed within hours of the administration of the agent. Due to the affinity of praziquantel to the mucous membrane, the active ingredient protects against re-infestation to a limited extent.

In addition to oral administration in the form of tablets with a defined active ingredient content, transdermal application systems have also been developed, but these are used exclusively in veterinary medicine. For prophylaxis or treatment of worm infestation, praziquantel dissolved in water is dripped onto the skin of cats or dogs. The active ingredient is absorbed through the skin and enters the bloodstream. However, since only part of the substance is absorbed through the skin, oral application is the standard therapy and means of choice for worm infestation in the gastrointestinal tract. The aim of praziquantel therapy is the complete killing and elimination of parasites at every stage of development.

The mechanism of action of praziquantel has also been scientifically proven. The quinoline praziquantel attaches to the mucous membrane surface of parasites and opens their calcium channels. The muscles then overcontract very quickly, leading to spastic paralysis of worms or leeches, which leads to the death of the parasite. However, that's not the only mechanism of action.

Because praziquantel also attacks the intact skin of the parasite and permanently disrupts its metabolism. This enables the pest to be better recognized and attacked by the host's immune system. In the event of an internal worm infestation, the killed parasites are simply excreted with the stool. If the active ingredient gets into the blood, it is distributed in all organs and organ systems. The effectiveness is fully retained, which is why praziquantel is also well suited for therapy in the case of extraintestinal worm infestation, for example in the brain. In order to kill parasites safely, a certain dose per kilogram of body weight must be achieved.

10-25 mg of praziquantel as a single dose per kilogram of body weight are sufficient to kill worms in the gastrointestinal tract. In the case of systemic infestation, higher doses, which as a rule also have to be given several times, must be selected. Systemic praziquantel therapy in humans must always be carried out under strict medical supervision. In the western industrial nations, the infestation with parasites in humans has decreased considerably in the last decades. Praziquantel therefore plays a bigger role in veterinary medicine.

However, worm diseases are still widespread in developing countries. Praziquantel is used here with great success, for example against the dangerous worm disease schistosomiasis. The active ingredient is also approved in pediatrics from a body weight of at least 20 kg.

Risks, side effects & dangers

Side effects and intolerance reactions may occur during praziquantel therapy. Adverse effects are often due to overdosing. Vomiting, nausea and abdominal pain, but also weakness, wheals on the skin or itching can be signs of an overdose or hypersensitivity to the treatment.

In these cases, praziquantel should be discontinued immediately and replaced with a similarly acting antihelminthic. Patients treated with the active ingredient also report muscle pain, loss of appetite, dizziness and tiredness. Since the praziquantel therapy is only given as a single dose in many cases and is very short, these side effects usually disappear quickly. It is known that some drugs for epilepsy and malaria can significantly reduce the active substance content of praziquantel. These drug groups should therefore not be taken at the same time.

In addition, praziquantel is incompatible with the antibiotic rifampicin, which can lead to unexpected chemical interactions. Both substances should also under no circumstances be taken together. During pregnancy and breastfeeding, praziquantel may only be used in justified exceptional medical cases. The active ingredient passes into breast milk and can harm the unborn child. Patients with previous illnesses such as cardiac arrhythmias or with impaired kidney or liver function must either not take praziquantel at all or only after the express instructions of the doctor.

The pharmacological agent cimetidine leads to an accumulation of praziquantel in the blood. If both substances are taken at the same time, the praziquantel concentration in the blood can rise sharply, and its half-life is also increased, since cimetidine makes it difficult for the liver to break down praziquantel.