Parasites Explained: Ivermectin, Mebendazole, & More 

By: Physicians Preference RX

When you hear the word parasites, you might imagine something out of a survival show. But parasites don’t just exist in remote jungles or on reality TV—they’re part of everyday life. Kids can pick them up at school, pet owners can be exposed through their animals, and travelers may bring them home after a trip abroad. Even in the U.S., parasites remain a quiet but common concern. 

Thankfully, trusted medications like ivermectin and mebendazole have been used for parasitic infections and prevention for decades. And when your provider prescribes them, Physicians Preference Pharmacy can prepare customized versions that are accurate, safe, and made to fit your exact needs. 

Parasites in Everyday Life 

Parasites are living organisms that survive at the expense of their host. In humans, they usually appear as: 

• Worms (helminths): pinworms that spread among children, hookworms from soil, or roundworms from pets. 
• Protozoa: microscopic parasites that can cause stomach issues, often after travel. 
• Ectoparasites: lice and mites that live on the skin. 

Parasites can show up in the most ordinary situations. A child who suddenly can’t stop scratching at night, a traveler returning with diarrhea or stomach cramps, a pet that brings germs inside after a romp in the yard, or even a gardener exposed to microscopic organisms in the soil—all are everyday examples of how parasites sneak into our lives. 

Why Parasites Matter More Than You Think 

Pinworms infect millions of Americans each year, most often children in daycare or schools¹. Globally, nearly one billion people are affected by soil-transmitted worms like hookworms². Even though parasites aren’t always dangerous, they can cause enough discomfort to affect your energy, focus, or sleep. 

Recognizing the possibility of parasites helps people seek the right care sooner, and that often means talking with a provider about prescription medications. 

Ivermectin: A Trusted Option 

From Soil Discovery to Global Use 

Ivermectin’s story began in the 1970s, when scientists discovered it in soil samples. Today, it’s considered one of the most important antiparasitic medications worldwide. The World Health Organization even includes it on the list of “essential medicines” because of its long-standing safety record³. 

When Providers Prescribe It 

• FDA-approved: river blindness, strongyloidiasis, and head lice. 
• Commonly prescribed off label: scabies, whipworms, and mites that live in hair follicles. 

Why Custom Dosing Helps 

Commercial ivermectin usually comes in small 3 mg tablets. Because dosing is weight-based, many people need to swallow several at once. Physicians Preference Pharmacy compounds ivermectin into capsules in 3-mg increments that match your prescribed dose exactly—meaning one capsule, not a handful. 

For skin concerns, ivermectin can also be compounded into topical creams that you simply rub on the affected area. 

Safety Snapshot 

Most people tolerate ivermectin well. Mild dizziness or stomach upset may occur, and creams may cause slight redness or itching⁴. At Physicians Preference Pharmacy, compounded versions avoid unnecessary fillers, making them cleaner and easier to tolerate. 

Mebendazole: A Reliable Classic 

How It Works 

Mebendazole starves parasites of their fuel. By blocking their ability to absorb glucose, it forces worms to die off naturally and leave the body⁵. 

When It’s Used 

• FDA-approved: pinworms, roundworms, hookworms, and whipworms. 
• Other uses: echinococcosis, trichinellosis, and toxocariasis⁶. 

Why Compounding Matters 

Commercial mebendazole has become difficult to access in recent years. That’s why Physicians Preference Pharmacy compounds it in custom strengths—100 mg, 200 mg, and 250 mg—so providers and patients have reliable options when it’s prescribed. Unfortunately, some people turn to fenbendazole, an animal medication not intended for human use. By offering compounded mebendazole, we provide a safe, human-grade prescription option that meets strict quality standards and supports patients under their provider’s care. 

Our Gold Standard 

Most pharmacies allow a ±10% margin for potency and weight. At Physicians Preference Pharmacy, we hold ourselves to ±3%. That means your prescription is consistently accurate, every time. 

Why Custom Prescriptions Make a Difference 

Real life rarely fits into “one size fits all.” Consider: 

• A child who struggles to swallow pills may need a liquid version. 
• An adult with allergies may need a filler-free formulation. 
• Someone prescribed a higher dose may prefer one capsule instead of ten small tablets. 

That’s where Physicians Preference Pharmacy comes in. We work with your provider to create medication that truly fits your needs—not just what’s available on the shelf. 

Don’t Rely on Animal Medications 

It may sound surprising, but some people try to use veterinary ivermectin or mebendazole when human versions aren’t accessible. This is dangerous. Animal medications may contain contaminants, unknown fillers, or completely inaccurate strengths. 

By contrast, Physicians Preference Pharmacy compounds prescriptions using certified human-grade ingredients and tests them for potency and safety. 

What to Expect: Safety and Side Effects 

Both ivermectin and mebendazole are generally well tolerated. Possible effects include: 

• Ivermectin: mild nausea, dizziness, or temporary skin irritation with creams. 
• Mebendazole: occasional stomach upset or rash. 

When parasites die, the body may react with short-term fatigue, rash, or digestive changes, similar to a Herxheimer reaction or a detox reaction.  These effects often pass quickly, but it’s important to discuss them with your provider. 

Why Choose Physicians Preference Pharmacy 

Physicians Preference Pharmacy is PCAB-accredited, which means we meet strict national standards. But we don’t stop there. We’ve set even higher internal benchmarks: 

• Outside potency testing every week. 
• ±3% standard for potency and weight (vs. the industry’s ±10%). 
• Certified ingredient sourcing only. 
• Transparent records for every batch we prepare. 

For over 20 years, patients and providers have trusted us to deliver safe, consistent compounded prescriptions. 

Key Takeaways 

• Parasites aren’t limited to distant places—they affect everyday life. 
• Ivermectin and mebendazole are trusted, long-standing medications. 
• Physicians Preference Pharmacy provides customized strengths and allergen-free options that fit individual needs. 
• Our strict ±3% quality standard ensures consistent accuracy in every prescription. 

If you have questions about ivermectin, mebendazole, or any of our compounded prescriptions, our pharmacists are here to help. You can reach Physicians Preference Pharmacy at 281-828-9088 to speak directly with a member of our team. It would be our pleasure to answer your questions and work with your provider to ensure your prescription is filled safely and accurately. 

References 

1. Centers for Disease Control and Prevention. Parasites – Enterobiasis (also known as Pinworm Infection). CDC, 2022. www.cdc.gov/parasites/pinworm. Accessed 24 Sept. 2025. 
2. World Health Organization. Soil-Transmitted Helminth Infections. WHO, 2023. www.who.int/news-room/fact-sheets/detail/soil-transmitted-helminth-infections. Accessed 24 Sept. 2025. 
3. Crump, Andrew, and Ōmura, Satoshi. “Ivermectin, ‘Wonder Drug’ from Japan: The Human Use Perspective.” Proceedings of the Japan Academy, Series B, vol. 87, no. 2, 2011, pp. 13–28. doi:10.2183/pjab.87.13. 
4. Chaccour, Carlos, et al. “Review of the Safety of Ivermectin.” American Journal of Tropical Medicine and Hygiene, vol. 102, no. 3, 2020, pp. 1–9. doi:10.4269/ajtmh.19-0994. 
5. Dayan, A. D. “Albendazole, Mebendazole and Other Carbamate Anthelmintics: Pharmacology and Therapeutic Use.” Drugs, vol. 50, no. 3, 1995, pp. 353–370. doi:10.2165/00003495-199550030-00003. 
6. Facts and Comparisons. Mebendazole Drug Monograph. Wolters Kluwer Clinical Drug Information, 2024.