Botulinum toxin type D blocks autonomic cholinergic synapses in humans: discussion of a potential therapeutic use

Based on epidemiological data it was believed that botulinumtoxin type D (BT-D) may not block human cholinergic synapses. We wanted to investigate BT-D's effect on the autonomic cholinergic synapse in humans. For this, we compared in four volunteers intraindividually the hypohidrotic effect of intradermal BT-D and BT-A in Minor's iodine starch sweat test. Altogether, we studied BT-D in doses of 4, 8, 16 and 32MU and BT-A in doses of 2, 4, 8 and 16MU at weekly intervals throughout a period of 13 weeks. All BT doses were diluted in 0.2 ml 0.9% NaCl/H₂O. Overall 704 data points were collected. Combined over all four subjects and all four doses BT-D's hypohidrotic effect intensity was half of BT-A's. BT-D's effect peaked around 5 weeks, BT-A's around 7 weeks. BT-D's effect duration was around 12 weeks, of BT-A's was around 14 weeks. For both BT types the hypohidrotic effect was dose dependent. BT-D, when injected intradermally, can block autonomic cholinergic synapses in humans. Compared to BT-A, BT-D's effect intensity was half and its effect duration was some 2 weeks shorter. With its weaker and shorter effect BT-D does not seem to promise therapeutic effects superior to BT-A.