Question

Drugs given to treat malaria are usually given in combination to attack the protozoan at various stages of it's life cycle.List three common drugs used to treat malaria.for each drug,describe it's therapeutic actions,indications,pharmacokinetics,contraindications,proper administration,common adverse reactions,and important drug-drug interactions.

Answer 1

1.Chloroquine

Classification
Therapeutic: antimalarials, antirheumatics (DMARDs)

Indications

Prophylaxis and treatment of acute attacks of malaria. Treatment of extraintestinal amebiasis. Unlabelled uses: Treatment of severe rheumatoid arthritis. Treatment of systemic lupus erythematosus.

Action:

Inhibits protein synthesis in susceptible organisms by inhibiting DNA and RNA polymerase. Therapeutic Effects: Death of plasmodia responsible for causing malaria. Death of amoeba responsible for causing amebiasis. Improvement in inflammation in rheumatoid arthritis and systemic lupus erythematosus.

Pharmacokinetics

Absorption: Well absorbed following oral administration. Distribution: Widely distributed; high tissue concentrations achieved. Crosses the placenta, enters breast milk. Metabolism and Excretion: 30% metabolized by the liver. Metabolite also has antiplasmodial activity; 70% excreted unchanged by the kidneys. Half-life: 3–5 days.

Contraindications and Precautions

Hypersensitivity. Hypersensitivity to other 4-aminoquinolones (hydroxychloroquine). Visual damage caused by chloroquine or other 4-aminoquinolones.

Lactation: Potential for serious adverse reactions in nursing infants .

Use Cautiously in: Liver disease. Alcoholism. Patients receiving hepatotoxic drugs. Porphyria (may exacerbate condition). Psoriasis. G6PD deficiency. Bone marrow depression. Hearing impairment. Epilepsy. Obstetric: Although safety not established, has been used. Pediatric: Extremely sensitive to chloroquine effects. Geriatric: May be predisposed to adverse effects).

Route and Dosage

Doses below expressed as chloroquine base: 1 mg of chloroquine base = 1.67 mg chloroquine phosphate or 1.25 mg chloroquine hydrochloride

• Suppression/Prophylaxis of Malaria
  • Oral (Children): 5 mg/kg once weekly, starting 2 wk prior to entering endemic areas and for 8 wk afterward (not to exceed 300 mg/day).If suppressive therapy is not initiated prior to entering endemic area, initial dose should be 5 mg/kg followed by another 5 mg/kg dose 6 hr later, followed by the usual dosage regimen
• Treatment of Acute Attack of Malaria
  • Oral (Children): 10 mg/kg initially (not to exceed 600 mg), then 5 mg/kg at 6 hr, 24 hr, and 48 hr after initial dose (not to exceed 300 mg/day)

Adverse Reactions and Side Effects

CNS: seizures, delirium, depression, headache, personality changes, psychosis. EENT: hearing impairment, retinopathy, tinnitus, visual disturbances. CV: cardiomyopathy, ECG changes (T-wave abnormalities, QRS prolongation), hypotension. GI: abdominal cramps, anorexia, diarrhea, nausea, vomiting. Derm: alopecia, dermatoses, photosensitivity, pigmentary changes, pruritus, skin eruptions. Hemat: agranulocytosis, aplastic anemia, leukopenia, thrombocytopenia. Neuro: neuromyopathy, peripheral neuritis, weakness.

Interactions

Drug-Drug: Antacids may decrease absorption . Blood levels may be increased by cimetidine,fluconazole,ketoconazole,clarithromycin,erythromycin,fluoxetine,nefazodone,paroxetine,protease inhibitors,quinidine,ritonavir, and verapamil. May decrease absorption of ampicillin (separate administration of these agents by at least 2 hr). May increase blood levels of cyclosporine,fluoxetine,lidocaine,mirtazapine,nefazodone,paroxetine,risperidone,ritonavir,thioridazine,tricyclic antidepressants, and venlafaxine. Blood levels may be decreased by carbamazepine,nevirapine,phenobarbital,phenytoin, and rifampin. May increase the risk of hepatotoxicity when administered with other hepatotoxic agents. Urinary acidifiers may increase renal excretion and decrease effectiveness. Drug-Food: Foods that acidify urine (see Appendix (Food Sources For Specific Nutrients)) may increase excretion and decrease effectiveness.

2.Primaquine phosphate:

Actions:
Disrupts the parasitic mitochondria, thereby interrupting metabolic processes requiring energy. Spectrum of activity includes preerythrocytic and exoerythrocytic forms of Plasmodium falciparum, P. malariae, P. ovale, and P. vivax. Nifurtimox (Lampit), an investigational drug available from the CDC, is preferred for intracellular parasites.

Indications
Primaquine phosphate is indicated for the radical cure (prevention of relapse) of vivax malaria.

Pharmacokinetics
Absorption: Well absorbed from GI tract.
Distribution: Distributed widely into liver, lungs, heart, brain, skeletal muscle, and other tissues.
Metabolism: Carboxylated rapidly in liver.
Excretion: Only small amount of drug excreted unchanged in urine. Plasma half-life is 4 to 10 hours

Contraindications
Contraindicated in patients with systemic diseases in which granulocytopenia may develop (such as lupus erythematosus or rheumatoid arthritis) and in those taking bone marrow suppressants and potentially hemolytic drugs.
Use cautiously in patients with previous idiosyncratic reaction (manifested by hemolytic anemia, methemoglobinemia, or leukopenia) and in those with family or personal history of favism, erythrocytic G6PD deficiency, or nicotinamide adenine dinucleotide (NADH) methemoglobin reductase deficiency.

Proper administration
Primaquine phosphate should be administered concurrently in order to eradicate the exoerythrocytic parasites in a dosage of 1 tablet (equivalent to 15 mg base) daily for 14 days.

Common adverse reactions
Gastrointestinal: nausea, vomiting, epigastric distress, and abdominal cramps.
Hematologic: leukopenia, hemolytic anemia in glucose-6-phosphate dehydrogenase (G-6-PD) deficient individuals, and methemoglobinemia in nicotinamide adenine dinucleotide (NADH) methemoglobin reductase deficient individuals.
Cardiac: Cardiac Arrhythmia and QT interval prolongation
Nervous System: Dizziness.
Skin and Soft Tissue: Rash, pruritus.

Important drug-drug interactions.
Caution while using with cardiac drugs
Drugs causing QT interval prolongation may have increased effect with Primaquine
Aluminum salts, magnesium: Decreases GI absorption.
Quinacrine: Potentiates toxic effects of primaquine.

3. Mefloquine HCl:

Actions:

Mefloquine is an antimalarial agent which works as ablood schizonticide. Mefloquine is active against the erythrocytic stages of Plasmodium species. However, the drug has no effect against the exoerythrocytic (hepatic) stages of the parasite. Mefloquine is effective against malaria parasites resistant to chloroquine.

Indications:
indicated for the treatment of mild to moderate acute malaria caused by mefloquine-susceptible strains of P. falciparum (both chloroquine-susceptible and resistant strains) or by Plasmodium vivax.

Pharmacokinetics:
The presence of food significantly enhances the rate and extent of absorption, leading to about a 40% increase in bioavailability.
It is extensively distributed to tissue.
Mefloquine is extensively metabolized in the liver by the cytochrome P450 system.
Mefloquine is excreted mainly in the bile and feces.

Contra indications:
It is contraindicated in patients with a known hypersensitivity to Mefloquine or related compounds (e.g., quinine and quinidine) or to any of the excipients contained in the formulation.
Mefloquine is contraindicated in patients with active depression, a recent history of depression, generalized anxiety disorder, psychosis, schizophrenia or other major psychiatric disorders, or with a history of convulsions.

Proper administration:
adults:
Five tablets (1250 mg) mefloquine hydrochloride to be given as a single oral dose. The drug should not be taken on an empty stomach and should be administered with at least 8 oz (240 mL) of water.
children:
20 to 25 mg/kg body weight. Splitting the total therapeutic dose into 2 doses taken 6 to 8 hours apart.

Common adverse reactions:
Dizziness, myalgia, nausea, fever, headache, vomiting, chills, diarrhea, skin rash, abdominal pain, fatigue, loss of appetite, and tinnitus.
Those side effects occurring in less than 1% included bradycardia, hair loss, emotional problems, pruritus, asthenia, transient emotional disturbances and telogen effluvium (loss of resting hair) and Seizures

Cardiovascular Disorders: circulatory disturbances (hypotension, hypertension, flushing, syncope), chest pain, tachycardia or palpitation, bradycardia, irregular pulse, extrasystoles, A-V block, and other transient cardiac conduction alterations
Skin Disorders: rash, exanthema, erythema, urticaria, pruritus, edema, hair loss, erythema multiforme, and Stevens-Johnson syndrome
Musculoskeletal Disorders: muscle weakness, muscle cramps, myalgia, and arthralgia
Respiratory Disorders: dyspnea, pneumonitis of possible allergic etiology
Other Symptoms: visual disturbances, vestibular disorders including tinnitus and hearing impairment, asthenia, malaise, fatigue, fever, sweating, chills, dyspepsia and loss of appetite

Important drug-drug interactions.
Because of the danger of a potentially fatal prolongation of the QTc interval, halofantrine must not be given simultaneously with Mefloquine.
Drugs prolonging QT interval must be avoided with this.
Anti seizure medications may have decreased effect if used along with this