Table 3

 Factors which may influence adverse effects with recreational drugs

*In my practice, the most common single neurological adverse effect of drug addiction is head trauma (for example, from baseball bats or gunshot wounds).
AVM, arteriovenous malformation.
Directly due to drug
• A high dose–sometimes because of an unusual source
• The speed of entry–especially intravenous or when smoked
• Individual sensitivity
• Chronic/repeated use–for example, cocaine, leads to longer half life
• Interaction with other compounds in the drugs
• Interaction with other drugs, including alcohol
• Interaction with pre-existing pathologies–hypertension, AVM, aneurysm, right to left cardiac shunt
Indirectly due to drug
• Secondary effects of coma or fits–especially if aspiration occurs
• Infection risks–easy portal of entry for pathogens
–impairment of the immune system
–exposures to pathogens such as HIV
• Accompanying lifestyle changes–alcoholism