Antiprotozoal Drugs: Uses, Side Effects and Types

Malaria

Causative agent: Plasmodium (a protozoan)

It has 5 species in human

• Plasmodium falciparum > 50% cases in India
• Plasmodium vivax
• Plasmodium ovale
• Plasmodium malariae
• Plasmodium knowlesi

NVBDCP – National Vector Borne Disease Control Programme

• Dengue
• Malaria: Female Anopheles
• Chikungunya
• Japanese encephalitis
• Lymphatic filariasis
• Kala-azar

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Antimalarial drugs

Fast acting drugs 

Chloroquine group

• Chloroquine
• Primaquine
• Amodiaquine
• Piperaquine

Artemisinin group

• Artesunate
• Artemether
• Arteether
• Arterolane

Intermediate-acting

(Mnemonic: Most Plasmodia Remain Lazy)

• Mefloquine
• Proguanil
• A racemic mixture of Quinine
• Lumefantrine

Slow acting

(Mnemonic: Plasmodia Can Die Slowly)

• Pyrimethamine
• Clindamycin
• Doxycycline
• Sulfadoxine

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Treatment of Malaria

Cure

Clinical Cure

To kill erythrocytic schizogony, which produces clinical symptoms. All species of Plasmodium. If incomplete: Recrudescence of Malaria. Remaining plasmodia divide again. Drugs: All drugs are effective except primaquine in erythrocytic schizogony.

Radical Cure

• To kill hypnozoites
• Only in P. vivax, P. ovale
• If incomplete, aka: Relapse of Malaria
• Wake up from dormant stage
• DOC: Primaquine
• New drug: Tafenoquine

Prophylaxis

Causal Prophylaxis

• To kill Pre-erythrocytic schizogony
• Not possible as the patient is asymptomatic
• Drugs (Mnemonic: PPD)
• Primaquine
• Proguanil
• Doxycycline

Suppressive prophylaxis

Suppressive prophylaxis is also known as traveler's prophylaxis. Given in patients traveling to the country possible malarial infection.

Non-endemic countries: 

• Arab countries
• Drug: Chloroquine
• Start 2 weeks before traveling
• After return, take for 4 weeks 600 mg weekly

Endemic countries:

• Southeast Asia region (chloroquine resistant)
• Drug: Mefloquine (DOC) or doxycycline

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Drugs Acting Against Various Stages

NVBDCP guidelines

P. vivax/Ovale

• Chloroquine + Primaquine
• Chloroquine given for 3 days for Clinical cure.
• Primaquine given for 13 days for Radical cure and as a gametocidal agent.

P. falciparum

• Most common infection in India, But it is chloroquine resistant
• ACT + Primaquine. ACT: Artemisinin-based combination therapy (clinical cure)
  • All Indian states
    • Artesunate + sulfadoxinepyrimethamine
    • Fast acting and slow acting combination
  • Except Northeastern states
    • Artemether + Lumefantrine
• Primaquine: Given as gametocidal as there is no hypnozoite stage in P. falciparum

Mixed infection

• P. vivax/ovale/falciparum
• ACT + Primaquine for 14 days

Other approved regimens for Chloroquine-resistant malaria

• Artesunate + Mefloquine
• Artesunate + Amodiaquine
• Artesunate + Pyronaridine (used in China)
• Arterolane + Piperaquine
• QDC regimen: Quinidine + Doxycline + Clindamycin, Given in Artemisinin allergic individuals

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Antimalarials in G6PD deficiency

• Antimalarials can cause damage and hemolysis of the RBC in G6PD deficiency. Most unsafe drug: (Mnemonic: PPQ)
  • Primaquine
  • Proguanil
  • Quinine
• Safer: Chloroquine
• Safest: Mefloquine

Complicated Malaria (Acute Severe Malaria)

P. falciparum causes complicated malaria

• loss of consciousness
• Life-threatening condition
• Injectable drugs are given in life-threatening conditions and in emergencies

Treatment

• DOC: IV Artesunate
  • Only Artemisinin can be given intravenously
  • Other Artemisinins are given intramuscularly
• 2nd: IM Artemether/Arteether
• 3rd: IV Quinine in 5%Dextrose solution
  • Quinine causes hypoglycemia

Malaria in Pregnancy

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Transfusion-Associated Malaria

In the blood, only erythrocytic schizogony is present, therefore, only clinical cure is given. No role for primaquine, as it is not effective in clinical cure since hypnozoites are absent. Drugs

• Chloroquine
• ACT

Chloroquine

Mechanism of Action

 Plasmodia eats hemozoin. Inside the food vacuole hemoglobin is converted into Hemozoin. Chloroquine inhibits the conversion of hemoglobin to hemozoin. Hemoglobin in increased amounts becomes toxic to plasmodia.

Resistance

• Plasmodium develops a transporter to efflux chloroquine outside the food vacuole
• P CRT (P Chloroquine Resistance f f Transporter)

Uses

• Protozoan infections
• Malaria
• Immunosuppressive action by decreasing immunity of the body
• Inhibits IL-1, 6, TNF alpha production
• Used in the treatment of autoimmune disease and hypersensitivity

Properties

• Oral and IV forms
• The volume of distribution: 15000 liters of plasma
  • VD is proportional to the amount of drug entering the organ
  • Deposits in various organs; therefore, hemodialysis has no role in chloroquine toxicity.

Uses of Chloroquine

• Malaria (Protozoa)
• Amebiasis (Amebic liver abscess)
• Leprosy reaction
• Atopic dermatitis
• Rheumatoid arthritis
• Infectious mononucleosis
• Autoimmune hemolytic anemia
• Giardiasis (Protozoa)
• DLE or SLE
• Photosensitivity on skin (Polymorphous light eruption)

Side effects of Chloroquine

• Skin: Hyperpigmentation
• Muscle: Myopathy
• CNS: Neuropsychiatric symptoms—Seizures, Psychosis
• Eye: Various ocular side effects affecting the lens, cornea and retina
• Ear: Ototoxicity (tinnitus and deafness)
• Heart: QT prolongation

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Artemisinin group

Obtained from Chinese herb called Artemisia annua , by Tu Youyou (Nobel prize)

Drugs:

• Artesunate
• Arterolane
• Artemether
• Arteether
• Di hydro Artesunate

ROA

• All are given orally except Artesunate which can be used IV (used in complicated malaria)
• Artesunate, Artemether, Arthether: IM
• Artesunate: rectally in children, and shock

Side effects

• Common: Nausea and vomiting
• Severe: Allergy (Hypersensitivity), Substitute with Quinine

Quinine

• Racemic mixture of L & D form of Quinine
• D form quinine is also known as Quinidine
  • Also used as Class IA antiarrhythmic drug
  • Blocks sodium and potassium channels in the heart
• Metabolized by CYP2D6

Side effects

• Most commonly diarrhea
• Hypoglycemia
  • Causes insulin release by blocking potassium channel on the pancreas
  • Always given with dextrose
• QT prolongation
  • Blocks potassium channel on heart
• Hypotension
  • Blocks alpha receptor
• Ototoxicity
  • aka: Cinchonism

Primaquine

• Effective in all stages of malaria except erythrocytic schizogony
• It is not effective in clinical cure

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Amebiasis

Causative agent Entamoeba histolytica

Luminal Amebicidal Drugs

Kills ameba cysts in the lumen

• DOC: Paromomycin
• Diloxanide furoate
• Quiniodochlor
• Iodoquinol

Tissue Amebicidal Drugs

• DOC: Metronidazole or its congeners
  • Used in Amebic dysentery and Amebic liver abscess
  • Chloroquine is an add-on drug for liver abscess
• Emetine

Trypanosoma

West African Type

Drug of choice 

• Early stage: Pentamidine
• Late stage: Eflornithine + Nifurtimox

New drug

• Fexinidazole: Effective in early, late stages

East African Type

Drug of choice 

• Early stage: Suramin
• Late stage: Pentamidine

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Pneumocystis jirovecii 

Opportunistic infection in HIV-positive individuals infecting the lungs and producing cavities. If CD4 count <200/mm³ the prophylaxis is started

Drugs

• DOC for treatment and prevention: Cotrimoxazole
  • TMP (Trimethoprim)/SMX(Sulfamethoxazole)
    • 80/200 mg daily or 160/200 mg thrice a week
  • Side effects of cotrimoxazole
    • Sulfa allergy
• Pentamidine aerosols
• Clindamycin + Primaquine (anti-malarial drug)
• Atovaquone (anti malarial drug) + Dapsone (leprosy drug)
• New drug: Trimetrexate
  • Similar to Methotrexate
  • Inhibit DHFR enzyme

Kala-azar (Visceral leishmaniasis)

Drugs according to NVBDCP guidelines for Kala-Azar

• L – AMB
  • Liposomal Amphotericin-B
  • DOC for Kala Azar
  • Most preferred
  • Give IV 10 mg/kg single dose
• Miltefosine (oral drug) + Paromomycin (injectable) Combination for 30 days
• Sodium stibogluconate: Least preferred, 20 mg/kg for 30 days

Trichomonas Vaginalis

• Female with abnormal yellow-green vaginal discharge. An unpleasant fishy smell. Strawberry cervix with punctate hemorrhage

• Metronidazole 2 g for 5-7 days
• Tinidazole
• Treat partner also single dose

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Giardiasis 

• Causes diarrhea in HIV-positive individuals
• DOC: Metronidazole/Tinidazole
• In pregnancy, DOC: Paromomycin
• Nitazoxanide is used in Immunocompetent patients

Toxoplasma Gondii

• Drug of choice: Sulfadiazine + Pyrimethamine
  • Antifolate drugs
  • Add folinic acid
• In sulfa-allergic patients, replace Sulfadiazine with clindamycin
• In pregnancy, it crosses the placenta and causes congenital defects.
  • Amniocentesis
    • IgM/IgG antibodies in amniotic fluid against toxoplasma gondii

- Positive: non treatable

- Negative: can prevent placental transmission with Spiramycin

Some Other Protozoans

Babesiosis

• Malaria like illness
• Mild: Atovaquone + Azithromycin
• Severe: Quinine + Clindamycin

Balantidium coli

• Amebiasis like infection
• DOC: Tetracycline

Cyclospora & Isospora

• Diarrhea in HIV-positive individuals
• DOC: Cotrimoxazole

Naegleria

• Amebic meningoencephalitis
• DOC: Amphotericin – B

Microsporidia

• Diarrhea in HIV – positive individuals
• DOC: Albendazole
• Topical ulcer: Keratitis
  • Drug of choice: Topical Fumagillin
• Severe sepsis, Inflammation, and allergy
  • Drug of choice: Thalidomide

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