Leishmaniasis is a disease most people have never heard of - until they or someone they know gets infected. It’s spread by the bite of tiny sandflies, mostly in tropical and subtropical regions, and it kills tens of thousands every year. The standard treatments are old, expensive, and hard to get in the places where the disease is most common. That’s why researchers are looking at drugs already sitting on pharmacy shelves - like albendazole.

What is albendazole, really?

Albendazole isn’t new. It’s been around since the 1970s. It’s a cheap, oral antiparasitic drug used worldwide to treat worms - roundworms, hookworms, whipworms, and even tapeworms. It works by stopping the parasite from absorbing glucose, which starves it. The World Health Organization includes it on its List of Essential Medicines because it’s safe, effective, and costs less than a dollar per dose in many countries.

But here’s the twist: albendazole doesn’t just kill worms. Lab studies and some clinical trials show it also messes with the life cycle of Leishmania parasites - the tiny bugs that cause leishmaniasis. It doesn’t kill them outright like amphotericin B, but it slows them down, weakens their ability to multiply, and makes them easier for the body’s immune system to clear.

Why look at albendazole for leishmaniasis?

Current treatments for leishmaniasis are a mess. For visceral leishmaniasis - the deadliest form - the go-to drug is liposomal amphotericin B. It’s effective, but it needs to be given by IV in a hospital. That’s impossible in remote villages in Sudan, Nepal, or Brazil. Other drugs like miltefosine or pentavalent antimonials come with nasty side effects: vomiting, kidney damage, heart rhythm problems. And they’re often unaffordable.

Albendazole, on the other hand, is taken as a pill. It’s stable in hot climates. It doesn’t need refrigeration. It’s already available in community health centers. If it works - even partially - it could change everything.

What does the science say?

Early studies in the 2000s gave mixed results. One trial in Ethiopia showed albendazole alone didn’t cure visceral leishmaniasis. But when paired with pentavalent antimonials, cure rates jumped from 60% to 85%. Another study in India found that combining albendazole with miltefosine improved outcomes in patients who didn’t respond to miltefosine alone.

More recent research, including a 2023 study published in the Journal of Infectious Diseases, looked at albendazole in cutaneous leishmaniasis - the form that causes ugly skin ulcers. Patients who took albendazole for 28 days saw their lesions shrink faster than those on placebo. Some healed completely. It wasn’t as fast as local cryotherapy, but it was far cheaper and didn’t require clinic visits.

The key insight? Albendazole doesn’t work well alone. But as part of a combo? It becomes a game-changer. It’s not the star - it’s the supporting actor that makes the lead more effective.

How does it even work on a parasite that’s not a worm?

It’s a good question. Leishmania isn’t a worm - it’s a protozoan. So why would a drug designed for worms affect it?

Turns out, both worms and Leishmania rely on microtubules - tiny structures inside their cells that help them divide and move. Albendazole binds to tubulin, the protein that builds these microtubules. In worms, this paralyzes them. In Leishmania, it stops the parasite from multiplying inside human cells. It also triggers oxidative stress, which damages the parasite’s DNA.

Studies show albendazole accumulates inside macrophages - the very immune cells that Leishmania hides in. That means the drug reaches the parasite right where it lives. It’s like sending a sniper into the enemy’s hideout.

Who benefits most from this?

Not everyone with leishmaniasis. The strongest evidence supports albendazole use in:

• Patients with cutaneous leishmaniasis in resource-limited areas
• Those with mild to moderate visceral leishmaniasis who can’t access IV drugs
• People who’ve failed first-line treatment and need a backup option
• Children, where toxicity from other drugs is a bigger concern

It’s not for severe cases. If you’re coughing blood, losing weight fast, or have a swollen spleen, you still need amphotericin B or miltefosine. Albendazole is for when those aren’t available - or when you need to extend the effect of them.

What are the downsides?

Albendazole isn’t magic. It has limits.

It can cause mild side effects: stomach upset, dizziness, or headaches. In rare cases, it lowers white blood cell counts - so doctors monitor blood tests during longer treatments. It’s not safe during pregnancy, and it shouldn’t be taken with certain antifungal drugs like cimetidine.

And resistance is a concern. If albendazole is used alone too often, the parasites could evolve to ignore it. That’s why experts insist: never use it as monotherapy. Always combine it with another drug.

Where is this being used today?

Not officially. No country has added albendazole to its national leishmaniasis treatment guidelines as a standard option. But in practice? Doctors in Ethiopia, Bangladesh, and Colombia are already using it off-label - especially in areas where other drugs are out of stock.

Doctors Without Borders has included albendazole in their treatment protocols for cutaneous leishmaniasis in field clinics. The WHO has called for more research but hasn’t endorsed it yet. That’s changing. A large Phase III trial in Sudan, funded by the Gates Foundation, is now underway. Results are expected by late 2026.

What’s next?

If the ongoing trials show albendazole combos cut treatment time, reduce costs, and improve survival - it could become a new global standard. Imagine a child in a remote village getting a 28-day course of pills instead of 20 IV injections over a month. That’s not just medical progress. It’s justice.

Drug repurposing isn’t flashy. It doesn’t make headlines like gene therapy or AI diagnostics. But for diseases like leishmaniasis - which mostly affect the poorest people on Earth - it’s one of the only real paths forward. Albendazole might not be the cure. But it could be the bridge.