Emily Anthes discusses memory dampening here, including some helpful information about ongoing, large scale trials of propranolol to treat PTSD in those who already have it. Here's an excerpt (footnote omitted):
Perhaps, researchers hypothesized, propranolol could weaken emotional memories if PTSD patients took the drug after they conjured up the details of a painful experience. By blocking the effects of norepinephrine and epinephrine upon recall, propranolol might dampen down activity in the amygdala and disrupt reconsolidation.
Initial tests of this idea have been promising. In these experiments, patients with PTSD are typically given propranolol either shortly before or after describing their traumas in detail. In a 2011 report on three trials, researchers reported that after six propranolol-recall treatment sessions, patients showed a significant decrease in PTSD symptoms. Larger clinical trials are now underway, including Aikins’s study, in which female veterans with PTSD will receive either propranolol or a placebo after thinking about their wartime experiences. Four weeks later, Aikins will measure the veterans’ physiological responsiveness and their PTSD symptoms, looking for signs of improvement.