Background: The complexity of a medication regimen is related to the multiple characteristics of the prescribed regimen and can negatively influence the health outcomes of patients. Objective: To propose cut-off points in the complexity of pharmacotherapy to distinguish between patients with low and high complexities seen in a primary health care (PHC) setting to enable prioritization of patient management. Methods: This is a cross-sectional study, which included 517 adult and elderly patients, analyzing different cut-off points to define the strata of low and high pharmacotherapy complexities based on percentiles of the population evaluated. Data collection began with the solicitation of prescriptions, followed by a questionnaire that was administered by an interviewer. The complexity of a medication regimen was estimated from the Medication Regimen Complexity Index (MRCI). High complexity pharmacotherapy scores were analyzed from patient profiles, the use of health services, and pharmacotherapy. The criteria for subject inclusion in the sample population were as follows: inhabitant of the area covered by the municipality, 18 years or older, and being prescribed at least one drug during the collection period. Exclusion criteria at the time of collection were the use of any medication whose prescription was not available. All medications were accessed through the Primary Healthcare Service (PHS). Results: The median total pharmacotherapy complexity score was 8.5. High MRCI scores were correlated with age, medications taken with in the Brazilian PHS, having at least one potential drug-related problem, receiving up to eight years of schooling, number of medications and polypharmacy (five or more medicines), number of medical conditions, number of medical appointments, and number of cardiovascular diseases and endocrine metabolic diseases. We suggest different complexity tracks according to age (e.g., adult or elderly) that consider the pharmacotherapy and population coverage characteristics as high complexity limits. For the elderly patients, the tracks were as follows: MRCI≥25.4, MRCI≥20.9, MRCI≥17.5, MRCI≥15.7, MRCI≥14.0, and MRCI≥13.0. For adult patients, the limits of high complexity were MRCI≥25.1; MRCI ≥ 23.8; MRCI≥21.0; MRCI≥17.0; MRCI≥16.5; and MRCI≥15.5. Conclusion: The medication regimen complexity is associated with the patient's illness profile and problems with the use of drugs; therefore, the proposed scores can be useful in prioritizing patients for clinical care by pharmacists and other health professionals. © 2015, Grupo de Investigacion en Atencion Farmaceutica. All rights reserved.