McKenna's Pharmacology for Nursing, 2e

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C H A P T E R 1 3  Anthelmintic agents

Therapeutic actions and indications Anthelmintic agents are indicated for the treatment of infections by certain susceptible worms and are very specific in the worms that they affect; they are not inter- changeable for treating various worm infections. See Table 13.2 for usual indications for each of these agents. Anthelmintics interfere with metabolic processes in particular worms, as described previously. Figure 13.2 shows sites of actions for these drugs. Pharmacokinetics Mebendazole is available in the form of a chewable tablet, and a typical 3-day course can be repeated in experience. Swallow the tablets whole and avoid holding them in your mouth for any length of time because a very unpleasant taste may occur. • Common effects of this drug include • Nausea, vomiting and loss of appetite: Take the drug with food, and eat small, frequent meals. • Dizziness and drowsiness: If this occurs, avoid driving a car or operating dangerous machinery. Change positions slowly to avoid falling or injury.

3 weeks if needed. Very little of the mebendazole is absorbed systemically, so adverse effects are few. The drug is not metabolised in the body, and most of it is excreted unchanged in the faeces. A small amount may be excreted in the urine. Albendazole is poorly absorbed from the gastroin- testinal (GI) tract, reaching peak plasma levels in about 5 hours. It is metabolised in the liver and primarily excreted in urine. Ivermectin is readily absorbed from the GI tract and reaches peak plasma levels in 4 hours. It is completely metabolised in the liver with a half-life of 16 hours; excretion is through the faeces. • Report any of the following conditions to your healthcare provider: fever, chills, rash, headache, weakness or tremors. • Take all of the drug that has been prescribed. Never use this drug to self-treat any other infection or give it to any other person. • Tell any doctor, nurse or other healthcare provider that you are taking this drug. • Keep this drug and all medications out of the reach of children.

Cilia with microtubules

Golgi apparatus

Peroxisomes

Cell membrane

Lysosomes

Centrioles

Nucleus: Nuclear membrane Nuclear pore Nucleolus

Pyrantel causes paralysis and cell death

Microtubules Albendazole blocks tubule formation

FIGURE 13.2  General structure of a cell, showing the sites of action of the anthelmintic agents. Mebendazole interferes with the ability to use glucose, leading to an inability to reproduce and cell death. Albendazole blocks tubule formation, resulting in cell death. Ivermectin blocks calcium channels, leading to nerve and muscle paralysis and cell death. Pyrantel is a neuromuscular polarising agent that causes paralysis and cell death. Praziquantel increases membrane permeability, leading to a loss of intracellular calcium and muscular paralysis; it may also result in disintegration of the integument

Smooth endoplasmic reticulum Polyribosomes

Mitochondria Mebendazole prevents cell use of glucose

Ivermectin blocks calcium channels, leading to nerve and muscle paralysis and cell death

Rough endoplasmic reticulum

Praziquantel increases membrane permeability, causing cell death