02.15 Antiparasitic Agents

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  1. Antiparasitics- class of medications which treat parasitic diseases like those caused by helminths, amoeba, ectoparasites, parasitic fungi, and protozoa.
  2. Antiparasitic agents and their method of action
    1. Anthelmintics-antiparasitic drugs that rid of parasitic worms (helminths) and other internal parasites from the body by stunning or killing them without causing major damage to host organism.
      1. Not easily treated since the organism is an animal and has more incommon with human cells than viruses, bacteria and fungi.
        1. Some anthelmintics work by inhibiting metabolic processes that are vital to the parasite but absent or not vital in the host
        2. Other anthelmintics are poorly absorbed through the difestive system, which means the parasite is exposed to much higher concentrations of the anthelmintic than the host. Causing starvation or paralysis of the parasite which is usually expelled or digested.
          1. Antimetabolites-drugs that interfere with enzymes necessary for DNA synthesis.
          2. Antimetabolites can also act as chemicals that imitate purines and pyrimidines (nucleotide bases) which prevents nucleotides incorporating into DNA during the S phase/ blocking cell division.


Today we’re going to be talking about Antiparasitic Agents.


In this lesson on antiparasitic Agents we will cover exactly what antiparasitic agents are as well as discuss their method of action and even see a video of them at work! So let’s begin.

Antiparasitics treat parasitic diseases, which impact an estimated 2 billion people This makes these agents pretty darn important and their categories include include those that are Broad Spectrum, AntiProtozoals which attack Protists, Antihelminthic which attack worms, Antiamoebic which target amoebas, and even Antifungals…that are found to have an effect on other parasites.


So antiparasitics not only play a big role in treating billions, but they also have a big challenge in that their aim often times is to basically destroy and animal within an animal. Many of the of the nasty parasites are in the animal kingdom, like tapeworms or hookworms or in the kingdom protista which are more closely related to animals then say a fungus or bacteria. So treating something more closely related can be tricky because you have more biological processes in common.

Anthelmintics are designed to take down the Helminths better known as parasitic worms that are indeed animals. These drugs are designed to either stun or kill the worm without causing major damage to the host organism.


Some anthelmintics work by inhibiting metabolic processes that are vital to the parasite but absent or not vital in the host. Others are poorly absorbed through the GI system, acting on the parasite more than the host. So here is video footage of an anthelmintic called papein acting on a parasitic worm known as H. bakeri. You be able to see here towards the end of the video the worm develops a cyst that eventually erupts and the worm begins to leak its internal contents, which will ultimately kill it.

Other anthelmintics are Antimetabolite drugs that interfere with enzymes necessary for DNA synthesis.  additionally there are Antimetabolites that imitate nucleotide bases can block other nucleotides from incorporating into DNA halting cell division.  Both of these will eventually do away with the parasite in time.

So in review, antiparasitic agents are drugs that destroy organisms that cause disease.  They  can be broad or specific to the type of parasite they attack. Anthelmintics stun or kill parasitic worms and antimetabolites are designed to block cell processes specific to the parasite.

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