Drug Excretion in Breast Milk

Inclusion criteria 1. Healthy postpartum women 2. 18-50 years of age and their infants 3. Able to provide written informed consent Exclusion criteria 1. Receiving cimetidine within the 3 days prior to each study day. Concomitant administration of cimetidine will confound interpretation of study results. 2. Hypersensitivity to cimetidine Patients with known allergic reactions to cimetidine will be excluded for safety reasons 3. Receiving medication known to interact with cimetidine: OCT, BCRP, CYP3A4, CYP2D6, CYP1A2 and CYP2C9 substrates (e.g. amiodarone, clopidogrel, diazepam, ketoconazole, metformin, nifedipine, phenytoin, procainamide, theophylline,tricyclic antidepressants and warfarin) Patients with drug interactions will be excluded for safety reasons. 4. Receiving BCRP inhibitors/inducers (afatinib, aripipraxole, axitinib, cimetidine, cyclosporine, curcumin/tumeric, delavirdine, efavirenz, elacridar, elvitegravir, etravirine, FTC, 5-fluorouracil, fluvastatin, imatinib, lanzoprazole, lapatinib, lopinavir, maraviroc, nelfinavir, nebicapone, nilotinib, novobiocin, oltipraz, omeprazole, pantoprazole, phenobarbital, promazine, rabeprazole, riboflavin, rifampicin, risperidone, saquinavir, sirolimus, sorafenib, sulfasalazine, sunitinib, tacrolimus, tariquidar, telaprevir, telatinib, teriflunomide, tolcapone, triflunomide, trametinib, trifluoperazine, venlafaxine, zidonuvir), OCT1 inhibitors/inducers (acyclovir, amantadine, amiloride, amitriptyline, bucindolol, carvedilol, chlorpheniramine, chlorpromazine, cimetidine, citalopram, clonidine, clopidogrel, clotrimazole, clozapine, cocaine, corticosterone, cyclosporine, daclatasvir, darunavir, desipramine, dextromethorphan, diltiazem, disopyramide, dronedarone, efavirenz, famotidine, fentanyl, fluvoxamine, formoterol, fuloxetine, griseofulvin, doxazosine, ganciclovir, guanfacine, imipramine, indinavir, isavuconazole, itraconazole, ketoconazole, lamotrigine, lasmiditan, levofloxacin, levomepromazine, lidocaine, maprotiline, methylnicotinamide, morphine, moxifloxacin, nefazodone, nelfinavir, nevirapine, nicotine, nomifensine, ondansetron, oxybutynin, paroxetine, pentamidine, phenoxybenzamine, prazosin, probenecid, procainamide, propafenone, pyrazinamide, quetiapine,quinidine, quinine, reboxetine, remoxidpride, reseripine, rifampicin, ritonavir, salmeterol, saquinavir, tramadol, trimethoprim, trimipramine, verapamil) Inhibitors and inducers of the drug transporters will confound data analysis and interpretation. 5. Kidney disease could confound data analysis and interpretation. Therefore, patients with known kidney disease with documented renal function impairment will be excluded from the study. Current serum creatinine \> 1.2 mg/dL in their medical record will be excluded. 6. Known liver disease Liver disease will confound data analysis and interpretation. Therefore, patients with known significant liver disease will be excluded from the study. Current ALT exceeding 2-times the upper limit of normal in their medical record will be excluded. 7. Inability to fast for 4 hours prior to the study. To limit PK variability across study days, subjects will be requested to fast for 4 hours prior to each study day. 8. Smokers (tobacco or other nicotine containing products Nicotine interacts with OCT1 and will confound data analysis and interpretation