This thesis focuses on bioanalytical method development and validation of antileishmanial drugs amphotericin B, miltefosine, and paromomycin in human plasma and human skin tissue followed by clinical target site pharmacokinetic outcomes induced by these developed bioanalytical methods. Chapter 1 provides an overview of bioanalytical quantification methods of the most relevant antileishmanial used in human pharmacokinetic studies and clinical trials. It covers (liposomal) amphotericin B, miltefosine, paromomycin, pentamidine and pentavalent antimonials and summarizes sample preparation, calibration model, separation, and detection methods in various human matrices from identified published method validations and included future perspectives in the development of antileishmanial bioanalysis. Chapter 2 presents the development and validation of a modern bioanalytical method for the quantification of paromomycin in human plasma using ion-pair ultra-high performance liquid chromatography tandem mass spectrometry. It was the first bioanalytical assay that employed a stable isotope labelled internal standard in the quantification of paromomycin. The relevance of developing a sensitive method for the quantification of paromomycin in human plasma is discussed, furthermore its supporting role in clinical pharmacokinetic studies in patients suffering from visceral leishmaniasis in Kenya. Chapter 3 discusses and presents target-site bioanalytical methods for the quantification of antileishmanial drugs in human skin tissue. Chapter 3.1 provides an overview of existing skin tissue sample pre-treatment and homogenization techniques for quantification of pharmaceutical compounds. It discusses the advantages and disadvantages of certain homogenization techniques relative to the accuracy and recovery from skin tissue of the bioanalytical method. In chapter 3.2 the development and validation of a bioanalytical method for the quantification of miltefosine in human skin tissue is presented. It describes a detailed development of a homogenization method employing enzymatic digestion by collagenase A for human skin tissue sample processing. Furthermore, its clinical applicability to target-site pharmacokinetic studies in post-kala azar dermal leishmaniasis patients in Bangladesh is demonstrated. Chapter 3.3 focuses on the development and validation of a bioanalytical method for the quantification of amphotericin B in human skin tissue with a clinical application in post-kala azar dermal leishmaniasis patients in India. Finally, chapter 3.4 provides the development and validation of a bioanalytical method for the quantification of paromomycin in human skin tissue and a clinical application in a pharmacokinetic study in post-kala-azar dermal leishmaniasis patients in Sudan. Chapter 4 explores the pharmacokinetic outcomes of target-site pharmacokinetic studies employing human skin tissue data. Chapter 4.1 evaluates miltefosine pharmacokinetic and pharmacodynamic outcomes and presents the first skin tissue model characterizing the distribution of miltefosine from blood-based matrices to skin tissue from patients suffering from post-kala azar dermal leishmaniasis in India and Bangladesh. Chapter 4.2 presents a pharmacokinetic model for liposomal amphotericin B in both human plasma and skin tissue, exploring the target-site exposure and distribution of this antileishmanial drug based on clinical pharmacokinetic data of patients suffering from post-kala azar dermal leishmaniasis in India and Bangladesh. Chapter 5 summarizes and concludes the thesis and furthermore presents the authors’ views on future perspectives for the development of bioanalytical methods for antileishmanial drugs.