Ivermectin

How it works

It binds glutamate-gated chloride channels in invertebrate nerve and muscle cells, increasing chloride permeability and causing parasite paralysis and death.

Prescribing in practice

• In areas co-endemic for Loa loa, treatment can precipitate serious or fatal encephalopathy in patients with high microfilarial loads, so screen before treating.
• Onchocerciasis usually requires repeated dosing because the drug kills microfilariae but not adult worms.
• The mammalian central nervous system is normally protected by the blood-brain barrier, but caution applies in conditions that may compromise it.

Monitoring

No routine laboratory monitoring is required; observe for Mazzotti-type reactions when treating microfilarial infections.

Counselling the patient

• Itching, rash, swollen glands or joint aches can occur after treatment as parasites die.
• Further doses may be needed to fully clear the infection.
• Take oral ivermectin as directed and return for any planned repeat treatment.

Evidence & guidelines

Widely used in mass drug administration programmes for onchocerciasis; refer to the SPC and WHO guidance for indication-specific use.