Safety and Preliminary Efficacy of L-arginine in Severe Falciparum Malaria

Safety and Preliminary Efficacy, Pharmacokinetics, Pharmacodynamics of L-arginine in Severe Falciparum Malaria

Background: Mortality from severe malaria remains ~15% despite the use of the most rapidly parasiticidal antimalarial therapy, artesunate. Adjunctive treatments may improve outcome. Our overall goal is to determine if adjunctive treatment with L-arginine is safe and improves outcomes in severe malaria. In studies to date, we have shown that L-arginine is safe in moderately severe malaria, increases nitric oxide production and improves endothelial function. We now propose to extend these studies to patients with severe malaria.

Aims: To determine the safety, preliminary efficacy, pharmacokinetics and pharmacodynamics of L-arginine infusion in severe malaria.

Hypothesis: L-arginine will improve endothelial function, lactate clearance time and tissue oxygen delivery compared to saline with no clinically significant adverse effects.

Methods: Based on previous pharmacokinetic modeling and simulations, we propose a phase 2A randomised controlled trial of L-arginine vs saline in severe malaria, each given over 8 hours. If safety is demonstrated this will be followed by a phase 2B open-label study of 24-hour infusion of L-arginine in severe malaria with safety and preliminary efficacy compared with the 8 hour infusions given in phase 2A.

The primary outcomes will be the improvement in endothelial function and lactate clearance in patients given L-arginine infusion compared with those who received saline. Among the secondary outcomes will be safety and the effect of L-arginine vs saline on tissue oxygen delivery (NIRS).

Data from both phase 2A and 2B will be used to generate a pharmacokinetic/ pharmacodynamic model.

See brief summary

Inclusion Criteria:

1. age 18-60 years
2. informed consent obtained
3. time of commencement of artesunate ≤18 hrs before infusion of L-arginine
4. any level of P. falciparum parasitemia, and one or more of the following criteria: i. acute renal failure (creatinine >265umol/L) ii. hyperbilirubinemia (total bilirubin >50 umol/L) with either renal impairment (creatinine >130umol/L) or parasitemia of >100,000 parasites/uL iii. blackwater fever iv. hyperparasitemia (>10% parasitised red cells) v. cerebral malaria (Glasgow coma score <11) vi. Hypoglycemia vii. Respiratory distress (RR >32)

Exclusion Criteria:

1. pregnancy or lactation
2. diabetes
3. serious pre-existing disease (cardiac, hepatic, kidney)
4. systolic blood pressure <90 mmHg after fluid resuscitation
5. initial iSTAT test showing any of the following values: i. K+ > 5.5 meq/L ii. Cl- > 110 meq/L iii. HCO3- < 15 meq/L
6. known allergy to L-arginine
7. evidence of concurrent bacterial infection
8. concurrent therapy with any of the following medications: iv. spironolactone, v. oral nitrates, vi. phosphodiesterase inhibitor (eg sildenafil [Viagra]) vii. alpha-blocking antihypertensive agents (eg prazosin) viii. L-arginine