Sunday 12 June 2011

ANTIHELMINTHIC DRUGS


ANTIHELMINTHIC DRUGS
Overview
-     helminths are eukaryotic hermaphroditic parasitic worms that replicate sexually, either by heterologous fertilization (“sequential hermaphrodites”) or by autologous fertilization (“synchronous hermaphrodites”)
-     they may exist in 3 common forms


FORM         DESCRIPTION
EGG            - the inactive, fetal form of the helminth
- only occurs in some species of helminths (other species of helminths give birth to live larvae, see below)


LARVA      - the immature, non-reproductive form of the helminth


ADULT       - the mature, reproductive form of the helminth




DRUGS USED AGAINST NEMATODES


Overview
-     “roundworms”
-     species include

SPECIES                                                    DESCRIPTION ASCARIS LUMBRICOIDES


ANCYCLOSTOMA DUODENALE NECATOR AMERICANUS ENTEROBIUS VERMICULARIS STRONGYLOIDES STERCORALIS TRICHURIS TRICHIURA TRICHINELLA SPIRALIS WUCHERERIA BANCROFTI
BRUGIA MALAYI

   
                                 ONCHOCERCA VOLVULUS




Relevant Drugs
-     7 types


DRUG NAME                             DESCRIPTION PYRANTEL                                                     General information
- an irreversible nicotinic receptor agonist
(“depolarizing neuromuscular blocking agent”,)
- irreversibly binds to nicotinic receptors at the neuromuscular junction, thus causing spastic paralysis of the helminths
- administered orally


Medical uses
- first-line treatment of ascaris lubricoides, ancyclostoma duodenale, necator americanus and/or enterobius vermicularis infection


Side effects
- vertigo
- nausea, vomiting and/or diarrhea


LEVAMISOLE                           General information
- same as pyrantel (see above)
- may cross the blood-brain barrier


Medical uses
- second-line treatment of ascaris lumbricoides, ancyclostoma duodenale, necator americanus and/or strongyloides stercoralis infection


Side effects
- vertigo
- nausea, vomiting and/or diarrhea
- mazzotti reaction (hypersensitivity reaction leading to fever, headache , skin rashes, myalgias and/or arthralgias caused by dying helminths)


MEBENDAZOLE                       General information
- a microtubule inhibitor
- binds to depolymerized tubulin, thus inhibiting the polymerization of tubulin into microtubules and following inhibition of microtubule-dependent glucose


uptake by the helminths
- administered orally


Medical uses
- first-line treatment of tricuris trichiura and/or trichinella spiralis infection
- second-line treatment of ascaris lubricoides, ancyclostoma duodenale, necator americanus, enterobius vermicularis and/or strongyloides stercoralis infection
- first-line treatment of echinococcus granulosus and/or ecchinococcus multilocularis infection (cestodes, see below)


Side effects
- nausea, vomiting and/or diarrhea
- epigastric pain


THIABENDAZOLE                   General information
- same as mebendazole


Medical uses
- first-line treatment of strongyloides stercoralis infection
- also used in the treatment of scabies due to sarcoptes scabiei infection


Side effects
- vertigo
- nausea, vomiting and/or diarrhea
- epigastric pain
- mazzotti reaction (see above)


DIETHYLCARBAMAZINE     General information
- inhibits the metabolism of arachidonic acid within the helminths, thus rendering the helminths susceptible to the host’s immune defense system
- administered orally


Medical uses
- first-line treatment of wuchereria bancrofti, brugia malayi and/or onchocera volvulus infection


Side effects
- headache

                                                                  - nausea, vomiting and/or diarrhea
- mazzotti reaction (see above)


IVERMECTIN                            General information
- a GABA agonist
- binds to presynaptic GABA receptors of the cholinergic neurons responsible for neuromuscular transmission, thus leading to hyperpolarization of the cholinergic neurons and following flaccid paralysis of the helminths
- administered orally


Medical uses
- first-line treatment of onchocera volvulus infection


Side effects
- mazzotti reaction (see above)


PIPERAZINE                              General information
- same as ivermectin (see above)


Medical uses
- second-line treatment of enterobius vermicularis infection


Side effects
- vertigo
- paresthesia
- motor disturbances
- bronchospasms
- nausea, vomiting and/or diarrhea




DRUGS USED AGAINST TREMATODES


Overview
-     “flukes”
-     species include

SPECIES                                               DESCRIPTION SCHISTOSOMA HEMATOBIUM


SCHISTOSOMA JAPONICUM

 

        SCHISTOSOMA MANSONI





Relevant Drugs
-     2 types


DRUG NAME            DESCRIPTION PRAZIQUANTEL                                     General information
- increases the permeability of the muscle cells to calcium, thus
leading to depolarization of the muscle cells and following spastic paralysis of the helminths
- administered orally


Medical uses
- first-line treatment of schistosoma hematobium, schistosoma japonicum and/or schistosoma mansoni infection
- first-line treatment of hymenolepis nana infection (cestodes, see below)
- second-line treatment of taenia solium, taenia sagginata and/or diphyllobothrium latum infection (cestodes, see below)


Side effects
- vertigo
- nausea, vomiting and/or diarrhea
- mazzotti reaction (see above)


OXAMNIQUINE       General information
- interposes between adjacent base pairs in the DNA, thus causing an inability of DNA polymerase to move along the DNA during replication of helminthic cells
- administered orally


Medical uses
- second-line treatment of schistosoma hematobium, schistosoma japonicum and/or schistosoma mansoni infection


Side effects
- headache
- vertigo
- dysphoria
- convulsions
- nausea, vomiting and/or diarrhea
- mazzotti reaction (see above)


DRUGS USED AGAINST CESTODES


Overview
-     “tapeworms”
-     species include

SPECIES                                                          DESCRIPTION ECHINOCOCCUS GRANULOSUS


ECHINOCOCCUS MULTILOCULARIS TAENIA SOLIUM
TAENIA SAGGINATA DIPHYLLOBOTHRIUM LATUM HYMENOLEPIS NANA



Relevant Drugs
-     3 types


DRUG NAME             DESCRIPTION MEBENDAZOLE      General information
- a drug used against nematodes (see above)


PRAZIQUANTEL      General information
- a drug used against trematodes (see above)


NICLOSAMIDE         General information
- uncouples oxidative phosphorylation in the helminths
- administered orally


Medical uses
- first-line treatment of taenia solium, taenia sagginata and/or diphyllobothrium latum infection
- second-line treatment of hymenolepis nana infection



                                                          Side effects


                                                          - nausea and/or vomiting


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