Tratamento farmacológico e intervencionista do sistema nervoso simpático / Pharmacological and interventional treatment of sympathetic system

o sistema nervoso autônomo contribui diretamente para uma série de atividades biológicas e está envolvido em inúmeras doenças. A hiperatividade simpática é um dos vários mecanismos envolvidos na patogênese da hipertensão arterial sistêmica (HAS) primária. A transmissão da informação nervosa através de sinapses é mediada por agentes químicos específicos conhecidos como neurotransmissores, representados pela acetilcolina e pelas catecolaminas. O bloqueio dos receptores pré e pós-sinapse permite que a ação de fárrnacos alcance sua plenitude no controle dos portadores de hiperati vidade simpática. Um percentual significativo de hipertensos são resistentes ao tratamento farrnacológico. A denervação simpática renal surgiu como estratégia terapêutica adjunta no controle de hipertensos resistentes ao tratamento clínico. Nos últimos cinco anos, diversos estudos demonstraram resultados consistentes na redução da pressão arterial. Diversas outras condições clínicas associam-se à hiperatividade do sistema adrenérgico, tais como a insuficiência cardíaca, o diabetes mellitus, a doença renal crônica, a síndrome da apneia e hipopneia obstrutiva do sono e as arritmias cardíacas. Nestes contextos, a redução da atividade simpática renal também mostrou-se ser benéfica em estudos clínicos iniciais. Uma variedade de dispositivos dedicados foram e estão sendo desenvolvidos com o objetivo de ampliar a segurança e a eficácia do método, além de facilitar o procedimento. Estudos multicêntricos, prospectivos, randomizados e controlados em andamento investigam desfechos como mortalidade cardiovascular, infarto agudo do miocárdio e acidente vascular cerebral em longo prazo.

The autonomic nervous system contributes directly to a number of biological activities and is involved in numerous diseases. Sympathetic hyperactivity is one of several mechanisms involved in the pathogenesis of primary hypertension. The transmission through the nerve synapses is mediated by specific chemical agents known as neurotransmitters represented by the acetylcholine and catecholarnine. Blockade of specific pre-and post-synapse receptors allows the treatment of patients with sympathetic hyperactivity. A large proportion of hypertensive patients are resistant to pharmacological treatment. Renal sympathetic denervation emerged as adjunctive therapeutic strategy in controlling hypertension resistant to medical treatrnent. ln the last five years, several studies have shown consistent results in lowering blood pressure. Several other clinica! conditions are associated with hyperactivity of the adrenergic system such as heart failure, diabetes mellitus, chronic kidney disease, obstructive sleep apnea, polycystic ovary syndrome and cardiac arrhythrnias. ln these contexts, the reduction in renal sympathetic activity also proved to be beneficial in initial clinical studies. A substantial variety of dedicated devices have been developed in order to reduce variability between operators, reduce renal artery manipulation, improve vessel contact, reduce radiation exposure and procedure time, and therefore improving safety and efficacy. Mu!ticenter, prospective, randomized, controlled trials are ongoing to investigate long term outcomes such as cardiovascular mortality, acute myocardial infarction and stroke.

Pharmacokinetics and pharmacodynamics of guanfacine extended release in adolescents aged 13-17 years with attention-deficit/hyperactivity disorder.

The safety and efficacy of guanfacine extended release (up to 4 mg/day) for attention-deficit/hyperactivity disorder (ADHD) in children and adolescents aged 6-17 years is well documented. Data suggest that weight-adjusted doses of guanfacine extended release >0.08 mg/kg but ≤0.12 mg/kg, if tolerated, may provide additional clinical benefits. For many adolescents, such dosing would exceed 4 mg/day, the highest approved dose. This open-label multicenter study evaluated the safety, tolerability, and steady-state pharmacokinetics of guanfacine extended release at escalated forced doses ≤9 mg/day in adolescents (N = 31) aged 13-17 years with ADHD. Following doses of approximately 0.12 mg/kg, the highest weight group (>70-90 kg) exhibited lower mean clearance at steady-state than the lowest weight group (≥30-50 kg). Consistent with its known antihypertensive effects, guanfacine extended release was associated with dose-dependent decreases in blood pressure (BP) and heart rate (HR). The physiologic response of increased BP upon standing was blunted in a dose-related manner while the physiologic response of increased HR upon standing was not substantively affected. The most common treatment-emergent adverse events were somnolence, dizziness, and sinus bradycardia. These results, and those from prior studies, support further examination of the efficacy and safety of higher weight-adjusted doses of guanfacine extended release for ADHD.