Impact of Pregnancy on the Pharmacokinetics and Metabolism of Nicotinamide in Humans.

In preeclampsia models, nicotinamide (NAM) has protective effects in preeclampsia and is being evaluated as a therapeutic nutraceutical in clinical studies. NAM undergoes extensive hepatic metabolism by NAM N-methyltransferase to methylnicotinamide (MNA), which is subsequently metabolized to methyl-2-pyridone-5-carboxamide (M2PY) by aldehyde oxidase. However, the pharmacokinetics (PK) of NAM and its major metabolites has never been studied in pregnant individuals. Blood samples were collected before and 1, 2, 4, 8, and 24 hr after single 1g oral NAM dose in healthy pregnant (gestational age 24-33 weeks) and nonpregnant female volunteers (n=6/group). Pooled urine was collected from 0-8 hr. NAM, MNA and M2PY area under the concentration-time curve (AUC) data were analyzed by noncompartmental analysis. No difference in the plasma AUC 0→24 of NAM (median [25%-75%]: 463 [436-576] vs 510 [423, 725] μM*hr, p=0.430) and its intermediate metabolite MNA (89.1 [60.4, 124.4] vs 83.8 [62.7, 93.7] μM*hr, p=0.515) was observed in pregnant and nonpregnant volunteers, respectively; however, the terminal metabolite M2PY AUC 0→24 was significantly lower in pregnant individuals (218 [188, 254] vs 597 [460, 653] μM*hr, p<0.001). NAM renal clearance (CL R ) (p=0.184), MNA CL R (p=0.180), and total metabolite formation clearance (CL form ) (p=0.405) did not differ across groups; however, M2PY CL R was significantly higher in pregnant individuals (10.5 [9.3-11.3] vs 7.5 [6.4-8.5] L/hr, p=0.002). These findings demonstrate that the PK of NAM and systemic exposure to its intermediate metabolite MNA are not significantly altered during pregnancy, and systemic exposure to NAM's major metabolite M2PY was reduced during pregnancy due to increased renal elimination.