Anti-Protozoals Flashcards
(49 cards)
What is Trypanosomiasis?
Human African trypanosomiasis (sleeping sickness) is a widespread tropical disease that can be fatal if not treated. It is spread by the bite of an infected tsetse fly.
What are the causative microorganisms in Trypanosomiasis?
Trypanosoma brucei and Trypanosoma rhodensiense.
What are the symptoms of Trypanosomiasis in the early stages of infection?
When a person is infected the bite erupts into a red sore and within a few weeks the person can experience fever, swollen lymph glands, aching muscles and joints, headaches and irritability.
What are the symptoms of Trypanosomiasis in the late stages of infection?
. In advanced stages, the disease attacks the central nervous system (crosses the BBB), causing changes in personality, alteration of the biological clock, confusion, slurred speech, seizures, and difficulty walking and talking. If not treated, the person will die.
Why do the drugs used to treat protozoal infections have side effect profiles that are much worse than other drugs for other illnesses?
Because the countries where these illnesses are most prevalent are some of the poorest countries in the world so there isn’t the market pull to develop new drugs with more acceptable side effect profiles.
What agents are used to treat Trypanosomiasis?
Pentamidine, Berenil, Eflornithine, Tryparsamide, Melarsoprol.
Describe the drugs used to treat the first stage of Trypanosomiasis (before the infection crosses the BBB).
The drugs used here are of lower toxicity and are easier to administer.
Describe the drug used to treat the second stage of Trypanosomiasis (after the infection crosses the BBB).
Second stage drugs have to cross the BBB to reach the parasite, these drugs are toxic and hard to administer.
What are the side effects of pentamidine used to treat Trypanosomiasis?
Liver and kidney dysfunction, hypertension, hypotension, hypoglycaemia, hypokalemia, leukopenia, thrombocytopenia, anaemia, allergic reactions.
How well tolerated is pentamidine?
Very well, despite its awful side effect profile.
How does pentamidine work against Trypanosomiasis infections?
It is thought the drug interferes with nuclear metabolism leading to inhibition of the synthesis of DNA, RNA, phospholipids, and proteins.
Why is suramin used parenterally in the treatment of Trypanosomiasis?
Because it is a polar drug and has poor bioavailability.
What undesirable effects does suramin have?
Allergic reactions and undesirable effects in the urinary tract.
How does suramin work to treat Trypanosomiasis?
It has trypanocidal activity due to the inhibition of enzymes involved in the oxidation of NADH which functions as a co-enzyme in many cellular processes such as respiration and glycolysis.
In what stage of Trypanosomiasis treatment is melarsoprol used?
Both stage one and stage two.
What heavy metal element is found in a molecule of melarsoprol?
Arsenic.
What side effects does melarsoprol exhibit?
Cutaneous reactions, polyneuropathy, diarrhoea, fever, reactive encephalopathy.
Eflornithine is a new treatment that only works in which strain of trypanosomiasis?
T. gambiense.
How does eflornithine work to treat Trypanosomiasis infections?
It is an irreversible inhibitor of the enzyme ornithine decarboxylase, a key enzyme in the conversion of ornithine to polyamines. Polyamines are essential for the synthesis of nucleic acids.
What is required of a patient for eflornithine to work to its full potential? Why might this not be possible?
An intact immune system. This might not be possible because this disease presents in countries where people have poor healthcare and many comorbidities.
Eflornithine is known to inhibit the human equivalent of the enzyme ornithine decarboxylase, why isn’t this a problem clinically?
Because the human enzyme half-life is less than that of the parasite’s so affected enzymes don’t remain in the system for long enough to have a clinically relevant effect.
What are the symptoms of leishmaniasis infection? What is the vector for the infection?
Cutaneous (sores) and visceral (liver and spleen) symptoms. The vector for this infection is the sand fly.
What drugs are used to treat leishmaniasis?
Amphotericin B, Sodium Stibogluconate.
How does amphotericin B work to treat leishmaniasis?
It is thought it works by creating complexes with cell membranes and creating pores, altering ion balance and leading to cell lysis and death.
