Calcium channel blockers (ex: verapamil) block the influx of calcium that normally drives the release of transmitters into the synapse. They do so by blocking the calcium channels. 

Calcium channel blockers

The active ingredient in Botox, botulinum toxin, binds to specialized receptors in nicotinic cholinergic membranes and is transported into the cell, where it blocks calcium-dependent release of acetylcholine, resulting in muscle paralysis

Botulinum toxin

Amphetamines are a class of psychostimulant drugs that accelerate the transmission of messages between the brain and the body. While some forms are prescribed by doctors to treat conditions like Attention Deficit Hyperactivity Disorder (ADHD), they are also frequently produced and used illicitly, carrying a significant potential for abuse.

Amphetamines

Some drugs are able to alter synaptic transmitter release. This can be done through many ways but include the over stimulation and/or prevention of the release of transmitters. Some are even able to target specific transmitters. 

Bowdoin College

Even with an adequate supply of transmitters in vesicles in the presynaptic terminal, various agents or conditions can prevent the release if transmitters when an action potential reaches the terminal. Examples of this include: 
- The prevention of synaptic transmission 
- Alteration of synaptic transmitter release
- Alteration of transmitter release through modulation of presynaptic activity 

Drugs effects presynaptically on transmitter release

Breedlove, S. & Watson, N. (2017). Behavioral neuroscience, eighth edition. Oxford University Press.

Behavioral Neuroscience 8th Edition

Drugs can work to prevent axons from firing action potentials which prevents synaptic transmission. This can occur in many ways.

Drugs preventing synaptic transmission 

Drugs alteration of synaptic transmitter release

One way drugs can effect presynaptic transmitter release is through modifying the systems that the neuron uses to monitor and regulate its own transmitter release. This includes altering the auto-receptor that monitors how much transmitter has been release presynaptically. 

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