In general, patients seem to tolerate medicinal cannabis well but patients should be fully aware of the possible adverse effects. Typical side effects last a short time, are mostly benign, and resolve as tolerance builds. They mainly occur after the intake of high doses, or when medicinal cannabis is used in combination with other substances like alcohol or particular medications.
A review of the effects of the medicinal use of cannabinoids indicated that the most frequent categories of adverse effects relate to respiratory, gastrointestinal, and nervous system disruptions. The common acute side effects of high doses of cannabis occur quickly after consumption, including:
- Dry mouth
- Redness of the eyes
- Heightened appetite
- Mild euphoria
- Reduction of alertness of the user, especially in the few hours directly after consumption.
- Increased heart rate
- Lowering of blood pressure and dizziness
In general, all side effects will slowly decrease and then disappear within a few hours. This depends upon the dose taken and mode of administration.
When cannabis of unknown, often illegal, origin is used, there is always a chance the product is contaminated with pesticides, growth enhancers, heavy metals or microbes. These contaminants are very damaging to the health of a patient. Medicinal cannabis is quality controlled by an external, internationally certified laboratory. The results of the analysis of every batch are presented in a Certificate of Analysis (CoA). This level of quality assurance shows their products to be free of harmful contaminants. Moreover, using standardized medicinal cannabis products is critical to ensuring the same dose is taken each time. This reduces the risk of overdosing and consequently that of unwanted side effects.
Just like any other medicine, medicinal cannabis is certainly not without risks. The most important risk factors are
- Heart disease
- Pregnancy and lactation
- Liver disease
- Driving and operating machinery