Nematicides – Antihelmintic Drugs

00:00 So let's move on to the antihelminthic agents.

00:04 We'll start of with the nematodes.

00:06 So the nematicidal agents start off with albendazole.

00:11 It's probably first in alphabet but it's also first in choices.

00:15 It's a very, very good agent.

00:17 It inhibits microtubule assembly which is essential for the structural stability of the organism.

00:24 It kills the ova or eggs in ascariasis and these other agents.

00:30 It is also going to kill the larva in ascariasis and cysticercosis which is also called the pork tapeworm.

00:39 It is larvicidal in hookworm.

00:41 And it is also larvicidal in hydatid disease.

00:44 So we use this agent in a number of different types of infections that are listed there.

00:51 In terms of toxicity from this agent, because the agent is used for such a short duration or time, toxicity is really quite rare.

01:00 Sometimes we'll see a reversible drop in white cell count.

01:03 And sometimes we'll see a short time rise in liver enzymes with prolonged used.

01:08 But the times that we actually use this for prolonged usages is really quite rare.

01:13 So becomes mostly a non issue.

01:18 Diethylcarbamazine is quite an interesting drug.

01:23 We actually use it to immobilize the microfilariae by an unknown mechanism.

01:30 And it is used in eye worm.

01:31 So this is actually an image of an eye worm.

01:34 So you can actually see them in the square, in the iris of a patient.

01:41 It looks like a white line that actually moves around.

01:43 It's actually quite a horrific thing to see if you've ever seen it live.

01:48 Toxicity to this medication, reactions to proteins of dying filariae include fever, rash and ocular damage.

01:55 So it's not so much the drug itself that's causing the toxic reaction.

02:00 It's a fact that when these filariae are dying, those break down proteins are causing all kinds of reaction.

02:07 And that's where you get run into trouble.

02:11 Ivermectin is another well known agent.

02:15 It's a nematicidal.

02:17 This is cutaneous larva migrans and you will see this in your practice at some point or another.

02:23 These are worms that are actually under the skin.

02:25 It's one dose, so ivermectin is one dose.

02:29 It intensifies the GABA neurotransmission in the nematodes.

02:33 And the nematodes become spastic and immobilize.

02:36 And they can't feed.

02:38 They can't do anything and they die.

02:39 We use it in cutaneous larva migrans, strongylodiasis and filariasis.

02:49 Toxicity to ivermectin is quite rare.

02:52 Remember that the actual toxicity to the drug is almost non-existent because it's just a single dose.

02:58 Where you get the toxicity is from the dying worms.

03:01 And so the agents that are being released from the dying worms includes fever.

03:06 The side effects include fever, rash and ocular damage if it's in the eye.

03:11 Now this disgusting picture is an infection of ascariasis.

03:19 This was removed from a 4 year old child who ended up having a bowel obstruction.

03:23 And they couldn't figure out why.

03:25 And the found out that his valve was full of these worms.

03:27 So mebendazole is the treatment for this.

03:31 It's absorbed minimally.

03:34 So less than 10 percent of this agent can be absorbed from the bowel.

03:37 It inhibits microtubule synthesis.

03:40 And it also inhibits the glucose uptake in the nematodes so they die very quickly.

03:45 It is the primary drug for ascariasis, pinworm and whipworm.

03:49 And it is the backup drug for visceral or tissue larva migrans.

03:58 Thiabendazole is another nematicidal agent.

04:00 It's a structural cogener of mebendazole.

04:03 In terms of how it is working, it's absorb systemically and it has much more systemic side effects then the other agents.

04:13 It works through inhibiting microtubule synthesis and glucose uptake in nematodes.

04:18 It's an alternative for systemic infections things like strongyloides or trichinosis which are the adult worms.

04:25 In terms of toxicity GI irritation is quite common.

04:28 You can also get intrahepatic cholestasis, liver failure.

04:33 And in terms of neurological symptoms you can sometimes get headache, dizziness and drowsiness.

04:38 A drop in white count leukopenia is common.

04:42 Hematuria is something that we have to be aware of and can occur.

04:46 And allergic reactions not just to the dying organisms but also to the drug itself are also present.

04:52 You can also get a Stevens Johnson syndrome which can be fatal.

04:57 We're not entirely sure if this is due to the drug itself or if it's due to the dying organisms, we haven't quite figured that one out yet.

05:05 And any rate be quite aware that this is a potential problem with this agent.