PRECAUTIONS
Blood Monitoring
Since anemia, methemoglobinemia, and leukopenia have been observed following administration of large doses of primaquine, the adult dosage of 1 tablet (= 15 mg base) daily for fourteen days should not be exceeded. In G6PD normal patients it is also advisable to perform routine blood examinations (particularly blood cell counts and hemoglobin determinations) during therapy.
If primaquine phosphate is prescribed for an individual who has shown a previous idiosyncratic reaction to primaquine phosphate as manifested by hemolytic anemia, methemoglobinemia, or leukopenia; an individual with a family or personal history of hemolytic anemia or nicotinamide adenine dinucleotide (NADH) methemoglobin reductase deficiency, the person should be observed closely. In all patients, the drug should be discontinued immediately if marked darkening of the urine or sudden decrease in hemoglobin concentration or leukocyte count occurs.
Potential Prolongation Of QT Interval
Due to potential for QT interval prolongation, monitor ECG when using primaquine in patients with cardiac disease, long QT syndrome, a history of ventricular arrhythmias, uncorrected hypokalemia and/or hypomagnesemia, or bradycardia (<50 bpm), and during concomitant administration with QT interval prolonging agents (see DRUG INTERACTIONS, ADVERSE REACTIONS, and OVERDOSE).
Carcinogenesis, Mutagenesis, Impairment Of Fertility
No carcinogenicity studies have been conducted with Primaquine. No fertility studies have been conducted with Primaquine. Primaquine is reported in the literature to be a weak genotoxic agent which elicits both gene mutations1, chromosomal damage and DNA strand breaks2. The publications reported positive results in the in vitro reverse gene mutation assays using bacteria (Ames test)3 4 and in the in vivo studies using rodents (mouse bone marrow cell sister chromatid exchange, mouse bone marrow cell chromosome abnormality, and rat DNA strand-breaks in multiple organs) 2 5. The genotoxicity data obtained in vitro and in rodent models are suggestive of a human risk for genotoxicity with primaquine administration (see WARNINGS, Usage In Pregnancy).
Geriatric Use
Clinical studies of primaquine did not include sufficient numbers of subjects aged 65 and over to
determine whether they respond differently from younger subjects. Other reported clinical
experience has not identified differences in responses between the elderly and younger patients.
In general, dose selection for an elderly patient should be cautious, usually starting at the low end
of the dosing range, reflecting the greater frequency of decreased hepatic, renal, or cardiac
function, and of concomitant disease or other drug therapy.
REFERENCES
1. Shubber EK, Jacobson-Kram D, Williams JR. Comparison of the Ames assay and the induction of sister chromatid exchanges: results with ten pharmaceuticals and five selected agents. Cell Biol Toxicol.1986; 2:379-99.
2. Chatterjee T, Muhkopadhyay A, Khan KA, Giri AK. Comparative mutagenic and genotoxic effects of three antimalarial drugs, chloroquine, primaquine and amodiaquine. Mutagenesis. 1998; 13:619-24.
3. Marss TC. Bright JE, Morris BC. Methemoglobinogenic potential of primaquine and its
mutagenicity in the Ames test. Toxicol Lett. 1987; 36:281-7.
4. Ono T, Norimatsu M, Yoshimura H. Mutagenic evaluation of primaquine, pentaquine and
pamaquine in the Salmonella/mammalian microsome assay. Mutat Res. 1994;325:7-10.
5. Giovanella F, Ferreira GK, de Prá1 SDT, Carvalho-SilvaM, GomesLM, Scaini G, Gonçalves RC4, Michels M, Galant LS, Longaretti LM, Dajori AL, AndradeVM, Dal-Pizzol F, Streck EL, de Souza RP. Effects of primaquine and chloroquine on oxidative stress parameters in rats. Anais da Academia Brasileira de Ciências (Annals of the Brazilian Academy of Sciences). 2015; 87: 1487-1496.