Modafinil is a DAT inhibitor. Taking it will reduce the amount of amphetamine getting into neurons, effectively reducing or blocking the effects of the amphetamine because it can’t access the parts of your brain that it uses to operate.
Your ‘friend’ was probably into overdose territory and the Modafinil antagonized the d-amphetamine while also inducing a wakefulness effect.
I really hope your friend realizes how bad this was.
Amphetamine is primarily absorbed through the plasma membranes and not DAT since it’s lipid soluble.
Dopamine does not and thus relies on DAT. By inhibiting DAT (as both amphetamine and Modafinil do), you increase extracellular dopamine.
Next, DAT does not “transport amphetamine around the brain”. It only transports it from the post synaptic cleft into the cell.
Also Modafinil is a much weaker DAT inhibitor than amphetamine itself as far as we know.
Lastly, drugs don’t “antagonize” other drugs. That word is a specific term used for the action on the receptor level.
The dopaminergic effects of Modafinil aren’t well known and are thought to be mild. It’s simply misinformation to claim that modafinil was somehow blocking the effects of amphetamine on the dopamine receptors.
Your ‘friend’ was probably into overdose territory and the Modafinil antagonized the d-amphetamine while also inducing a wakefulness effect.
I really hope your friend realizes how bad this was.