You have asked about "chemical changes of consciousness'' or drugs, and if these may ever be utilized in Krishna's service. To change consciousness, therefore the Spiritual Master is there. Do not do anything whimsically, like taking these drugs, that will ruin everything. Because you are imperfect you require help from the Perfect, and anything material like drugs is imperfect, so do not be distracted by contemplating in this way.
Letter to Visvambhara, 14 December, 1972