Abstract: The invention provides means to determine the predisposition of individuals to adverse drug reactions (ADRs). The methods are based on genotyping or parallelized enzyme and protein profiling or both. Parallelized enzyme activity profiling can be used for drug screening and development. As examples of the invention we show the prediction of adverse drug reactions of pulmonary hypertension patients by identifying genes and alleles linked to known ADRs and liver enzyme reaction profiling with ADR correlation.