A drug interaction is a drug situation in which the activity of a drug is affected by another substance (usually another drug) when both are administered together. Due to its broad range of effects, Cannabis can cause a variety of interaction effects with many over-the-counter and prescription medications, as well as most recreational drugs. This pamphlet contains a series of generalized guidelines intended toinform about possible side effects that can occur with the various major classes of drugs.
Under no circumstances should any person augment or substitute any prescribed medication with another registered drug or other (alternative, complementary or herbal) treatment without first consulting with a healthcare professional. This pamphlet is intended solely as an introduction to the most common drug interactions and is by no means an exhaustive exploration of the possible dangers inherent in modifying an ongoing pharmaceutical regimen.
Central nervous system (CNS) depressants, sometimes referred to as sedatives and tranquilizers, are substances that slow brain activity. This property makes their use common in the treatment of anxiety and sleep disorders. Most prescription pain medications have depressant effects in addition to their analgesic qualities. Alcohol and illegal recreational drugs such as ketamine and heroin (sometimes known as “downers”) also act as CNS depressants.
Cannabis can increase the effects of these substances in a synergistic (more than additive) manner. This can be both highly desirable and highly dangerous. Lower doses of medications such as morphine can be used in association with cannabis to achieve a comparable amount of pain relief due to magnification of both their effects. This same increase in effect is seen to some extent in all depressants. This can lead to clumsiness, drowsiness, dizziness, nausea, emesis (vomiting) and loss of consciousness. Therefore, great care should be taken with dosage when combining cannabis with any sort of depressant.
Antiepileptic drugs (also known as antispasmodics or anticonvulsants) are a diverse group of pharmaceuticals used in the treatment of epileptic seizures. They are also increasingly being used in the treatment of bipolar disorder, since many seem to act as mood stabilizers, and for treatment of neuropathic pain.
Antiepileptic medications share memory loss related side effects with cannabis. Both in conjunction may increase the severity of these effects, increasing the likelihood of forgetting a timed dose of medication and therefore leading to the possibility of an increased number of seizures occurring.
Unfortunately, little is known about the interactions between many of these medications and cannabis. If the choice is made to introduce cannabis into a pre-existing regimen of antiepileptic drugs (especially combinations of such), great care should be taken to ensure a safe environment in the case of seizure and to make careful note of any changes in the frequency or severity of any seizures experienced.
CNS stimulants are substances that can increase physical activity, mental alertness and attention span. They are used to treat attention-deficit hyperactivity disorder (ADHD) and narcolepsy, and the most commonly used recreational drug in the world -caffeine (coffee)– which is a stimulant. Excessive stimulant use can lead to tachycardia (abnormally fast heartbeat) thus putting at strain on the heart which can be dangerous for individuals with heart conditions. Cannabis can increase these effects when co-administered, which is a potential danger for those with a history of heart disease.
Antipsychotics are a diverse class of psychiatric medications primarily used to manage psychosis, particularly in schizophrenia and bipolar disorder, and are increasingly being used in the management of non-psychotic disorders.
Relevant data in regards to interactions between these medications and cannabis is lacking. Recent evidence suggests that antipsychotic treatment may have effects within the endocannabinoid system (the same system on which cannabis exerts an effect). However the clinical relevance of this is unclear.
While many individuals who suffer from schizophrenia self-medicate with cannabis, the majority of clinical data indicates an increase in the positive symptoms associated with schizophrenia (including delusions, hallucinations and disordered thoughts) in association with cannabis use. For patients with established schizophrenia, cannabis use is clinically associated with increased risk of relapse, and poorer adherence to the antipsychotic treatment.
These are drugs used for the treatment of major depressive disorders and other conditions, including dysthymia, anxiety disorders, obsessive compulsive disorders, eating disorders, chronic pain, neuropathic pain and, in some cases, dysmenorrhoea, snoring, migraines, attention-deficit hyperactivity disorder (ADHD), substance abuse and sleep disorders.
The majority of antidepressants fall within the bounds of four categories: selective serotonin reuptake inhibitors (SSRIs), serotonin-norepinephrine reuptake inhibitors (SNRIs), tricyclic antidepressants (TCAs) and monoamine oxidase inhibitors (MAOIs).
TCAs are of the most concern as they have been shown to cause abnormally fast heart rate known as tachycardia in a significant number of individuals.
There are also rare reports of tachycardia in association with SNRIs, but clinical data is currently lacking.
MAOIs are generally well tolerated in association with cannabis but have been anecdotally reported to increase cannabis’ psychotropic effects.
SSRIs generally do not interact with cannabis in any significant way.
|Special note about psychiatric medications
Psychiatric medications interact with the most sensitive and complex organ in the body: the brain. This means it should come as no surprise that unforeseen interactions can occur between cannabis and these drugs (especially when one has been prescribed a variety of different medications). Whenever adding ANYTHING psychoactive to an ongoing therapeutic regimen, the individual should first consult their healthcare provider.
At MediCanna we are well aware that your mental healthcare professional may be unwilling or unable to provide you with the information needed to make an educated choice about introducing cannabis into your medication regimen. We recommend against making such a move without professional advice. If you should choose to proceed regardless, during the first weeks of cannabis use in conjunction with either an ongoing or newly initiated regimen of psychiatric medications, a close watch should be kept over yourself for any irrational thoughts, inappropriate emotional states, issues with sleeping, and any other un-usual or undesirable side effects.
During this time it can be useful (both for yourself and your healthcare provider) to maintain a daily journal recording the timing of both when you administer your medication and the timing and duration of any possible side effects. Should any significant effects occur, immediately cease medicating with cannabis and consult your healthcare provider.