ABSTRACT
Induction or inhibition of CYP3A4mediated metabolism by cannabis. It is not yet known whether the effects are dependent on the degree of cannabis consumption
Be aware. Watch for signs of toxicity, especially when cannabis use abruptly changes
CANNABIS ANALGESICS – OPIOIDS – alfentanil, fentanyl, methadone, codeine, dextromethorphan
Unpredictable changes in plasma concentration. Risk of toxicity or therapeutic failure, particularly of drugs with a narrow therapeutic index
Induction or inhibition of CYP3A4mediated metabolism by cannabis. It is not yet known whether the effects are dependent on the degree of cannabis consumption
Be aware. Watch for signs of toxicity, especially when cannabis use abruptly changes
CANNABIS ANTIARRHYTHMICS
CANNABIS AMIODARONE Unpredictable changes in plasma concentration. Risk of toxicity or therapeutic failure, particularly of drugs with a narrow therapeutic index
Induction or inhibition of CYP3A4mediated metabolism by cannabis. It is not yet known whether the effects are dependent on the degree of cannabis consumption
Be aware. Watch for signs of toxicity especially when cannabis use abruptly changes
CANNABIS PROPAFENONE Unpredictable changes in plasma concentration. Risk of toxicity or therapeutic failure, particularly of drugs with a narrow therapeutic index
Induction or inhibition of CYP3A4mediated metabolism by cannabis. It is not yet known whether the effects are dependent on the degree of cannabis consumption
Be aware. Watch for signs of toxicity especially when cannabis use abruptly changes
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DRUGS OF ABUSE CANNABIS
drugs with a narrow therapeutic index
Induction or inhibition of CYP3A4mediated metabolism by cannabis. It is not yet known whether the effects are dependent on the degree of cannabis consumption
Be aware. Watch for signs of toxicity especially when cannabis use abruptly changes
CANNABIS ANTICANCER AND IMMUNOMODULATING DRUGS
CANNABIS CYTOTOXICS – CYCLOPHOSPHAMIDE, DOXORUBICIN, IFOSFAMIDE, LOMUSTINE, VINCA ALKALOIDS
Unpredictable changes in plasma concentration. Risk of toxicity or therapeutic failure, particularly of drugs with a narrow therapeutic index
Induction or inhibition of CYP3A4mediated metabolism by cannabis. It is not yet known whether the effects are dependent on the degree of cannabis consumption
Be aware. Watch for signs of toxicity, especially when cannabis use abruptly changes
CANNABIS HORMONES AND HORMONE ANTAGONISTS – TAMOXIFEN
Unpredictable changes in plasma concentration. Risk of toxicity or therapeutic failure, particularly of drugs with a narrow therapeutic index
Induction or inhibition of CYP3A4mediated metabolism by cannabis. It is not yet known whether the effects are dependent on the degree of cannabis consumption
Be aware. Watch for signs of toxicity, especially when cannabis use abruptly changes
CANNABIS IMMUNOMODULATING DRUGS – CICLOSPORIN, CORTICOSTEROIDS
Unpredictable changes in plasma concentration. Risk of toxicity or therapeutic failure, particularly of drugs with a narrow therapeutic index
Induction or inhibition of CYP3A4mediated metabolism by cannabis. It is not yet known whether the effects are dependent on the degree of cannabis consumption
Be aware. Watch for signs of toxicity, especially when cannabis use abruptly changes
CANNABIS ANTICOAGULANTS – WARFARIN
Unpredictable changes in plasma concentration
1. Induction or inhibition of CYP3A4mediated metabolism by cannabis. It is not yet known whether the effects are dependent on the degree of cannabis consumption 2. Induction of CYP1A2mediated metabolism by any form of smoking. Foods (e.g. broccoli, cabbage, Brussels sprouts, chargrilled meat) also induce this isoenzyme
Be aware. Monitor INR closely, especially when cannabis use abruptly changes
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Mechanism Precautions
lithium
Mechanism uncertain Be aware and measure plasma lithium levels if indicated by clinical observations
CANNABIS FLUOXETINE Report of mania Mechanism uncertain and may not be due to an interaction
Be aware
CANNABIS FLUVOXAMINE ↓ levels, with risk of therapeutic failure
Induction of CYP1A2-mediated metabolism by any form of smoking. Foods (e.g. broccoli, cabbage, Brussels sprouts, chargrilled meat) also induce this isoenzyme
Watch for poor response to fluvoxamine; conversely, watch for toxic effects if a previously heavy cannabis user stops smoking
CANNABIS SERTRALINE, VENLAFAXINE
Unpredictable changes in plasma concentration. Risk of toxicity or therapeutic failure, particularly of drugs with a narrow therapeutic index
Induction or inhibition of CYP3A4mediated metabolism by cannabis. It is not yet known whether the effects are dependent on the degree of cannabis consumption
Be aware. Watch for signs of toxicity, especially when cannabis use abruptly changes
CANNABIS AMITRIPTYLINE, CLOMIPRAMINE, DESIPRAMINE, IMIPRAMINE, NORTRIPTYLINE
≠ risk of tachycardia. Heart rate may ≠ to 100-160 beats per minute, with some records of 300 beats per minute resistant to verapamil therapy
Additive antimuscarinic effect Ask patients about cannabis use if they present with otherwise unexplained tachycardias while taking these drugs
CANNABIS TCAs Unpredictable changes in plasma concentration. Risk of toxicity or therapeutic failure, particularly of drugs with a narrow therapeutic index
Induction or inhibition of CYP3A4mediated metabolism by cannabis. It is not yet known whether the effects are dependent on the degree of cannabis consumption
Be aware. Watch for signs of TCA toxicity, especially when cannabis use abruptly changes
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Induction of CYP1A2-mediated metabolism by any form of smoking. Foods (e.g. broccoli, cabbage, Brussels sprouts, chargrilled meat) also induce this isoenzyme
Watch for poor response to mirtazapine; conversely, watch for toxic effects if a previously heavy cannabis user stops smoking
CANNABIS ANTIEMETICS – ONDANSETRON
↓ levels, with risk of therapeutic failure
Induction of CYP1A2-mediated metabolism by any form of smoking. Foods (e.g. broccoli, cabbage, Brussels sprouts, chargrilled meat) also induce this isoenzyme
Watch for poor response to ondansetron; conversely, watch for toxic effects if a previously heavy cannabis user stops smoking
CANNABIS ANTIHISTAMINES – BROMPHENIRAMINE, CHLORPHENIRAMINE
≠ risk of tachycardia. Heart rate may ≠ to 100-160 beats per minute, with some records of 300 beats per minute resistant to verapamil therapy
Additive antimuscarinic effect Ask patients about cannabis use if they present with otherwise unexplained tachycardias while taking these drugs
CANNABIS ANTIMUSCARINICS – ATROPINE, FLAVOXATE, HYOSCINE, OXYBUTYNIN, TOLTERODINE
≠ risk of tachycardia. Heart rate may ≠ to 100-160 beats per minute, with some records of 300 beats per minute resistant to verapamil therapy
Additive antimuscarinic effect Ask patients about cannabis use if they present with otherwise unexplained tachycardias while taking these drugs
CANNABIS ANTIOBESITY DRUGS – RIMONABANT
↓ most effects of cannabis that are due to its activity at central cannabinoid receptor
Rimonabant is a selective antagonist at central cannabinoid receptors, and thus the effects of either drug may be ↓
Be aware
CANNABIS ANTIPARKINSON’S DRUGS – PROCYCLIDINE, TRIHEXYPHENIDYL (BENZHEXOL)
≠ risk of tachycardia. Heart rate may ≠ to 100-160 beats per minute, with some records of 300 beats per minute resistant to verapamil therapy
Additive antimuscarinic effect Ask patients about cannabis use if they present with otherwise unexplained tachycardias while taking these drugs
DRUGS OF ABUSE CANNABIS
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Mechanism Precautions
HALOPERIDOL
clozapine may be halved), with the risk of therapeutic failure
Induction of CYP1A2-mediated metabolism by any form of smoking. Foods (e.g. broccoli, cabbage, Brussels sprouts, chargrilled meat) also induce this isoenzyme
Watch for poor response to these antipsychotics; conversely, watch for toxic effects of these antipsychotics if a previously heavy cannabis user stops smoking
CANNABIS ANTIVIRALS – PROTEASE INHIBITORS – indinavir, nelfinavir, nevirapine, ritonavir, saquinavir
Cannabis may cause ↓ plasma concentrations of protease inhibitors, particularly indinavir and nelfinavir
Cannabis may cause inhibition or induction of CYP3A4 isoenzymes, which metabolize these protease inhibitors
Be aware. Regular monitoring of viral indicators is necessary
CANNABIS ANXIOLYTICS AND HYPNOTICS – BZDs – alprazolam, diazepam, midazolam, triazolam
Unpredictable changes in plasma concentration. Risk of toxicity or therapeutic failure, particularly of drugs with a narrow therapeutic index
Induction or inhibition of CYP3A4mediated metabolism by cannabis. It is not yet known whether the effects are dependent on the degree of cannabis consumption
Be aware. Watch for signs of toxicity, especially when cannabis use abruptly changes
CANNABIS BETA-BLOCKERS – PROPRANOLOL
↓ levels, with risk of therapeutic failure
Induction of CYP1A2-mediated metabolism by any form of smoking. Foods (e.g. broccoli, cabbage, Brussels sprouts, chargrilled meat) also induce this isoenzyme
Watch for poor response to propanolol; conversely, watch for toxic effects if a previously heavy cannabis user stops smoking
CANNABIS BRONCHODILATORS – THEOPHYLLINE
↓ theophylline levels, with risk of therapeutic failure (theophylline has a narrow therapeutic range)
Induction of CYP1A2-mediated metabolism by any form of smoking. Foods (e.g. broccoli, cabbage, Brussels sprouts, chargrilled meat) also induce this isoenzyme. Although cannabis is considered to cause bronchodilatation, regular smoking leads to poorer respiratory function
Watch for poor response to theophylline; consider monitoring theophylline levels if a previously heavy cannabis user stops smoking, because of the risk of toxic effects
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DRUGS OF ABUSE CANNABIS
NISOLDIPINE
therapeutic failure, particularly of drugs with a narrow therapeutic index
Induction or inhibition of CYP3A4mediated metabolism by cannabis. It is not yet known whether the effects are dependent on the degree of cannabis consumption
Be aware. Watch for signs of toxicity, especially when cannabis use abruptly changes
CANNABIS VERAPAMIL Unpredictable changes in plasma concentration. Risk of toxicity or therapeutic failure, particularly of drugs with a narrow therapeutic index
1. Induction of CYP1A2-mediated metabolism by any form of smoking. Foods (e.g. broccoli, cabbage, Brussels sprouts, chargrilled meat) also induce this isoenzyme 2. Induction or inhibition of CYP3A4-mediated metabolism by cannabis. It is not yet known whether the effects are dependent on the degree of cannabis consumption
Watch for poor response to verapamil; conversely, watch for toxic effects if a previously heavy cannabis user stops smoking
CANNABIS DRUG DEPENDENCE THERAPIES
CANNABIS BUPROPION Unpredictable changes in plasma concentration. Risk of toxicity or therapeutic failure, particularly of drugs with a narrow therapeutic index
Induction or inhibition of CYP3A4mediated metabolism by cannabis. It is not yet known whether the effects are dependent on the degree of cannabis consumption
Be aware. Watch for signs of toxicity, especially when cannabis use abruptly changes
CANNABIS DISULFIRAM Risk of hypomania Mechanism uncertain and may be due to the presence of adulterants
Be aware
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Mechanism Precautions
cocaine, leading to enhanced subjective effects of cocaine (e.g. euphoria), and ≠ heart rate and other cardiac effects such as ischaemia
Attributed to cannabis-induced vasodilatation of the nasal mucosa, which leads to ≠ absorption of cocaine
Be aware. May be the cause of ischaemic cardiac pain in young adults
CANNABIS ECHINACEA AND OTHER IMMUNOSTIMULANTS
May ↓ immunostimulant effects The cannabinoid receptor is considered to mediate immunosuppressant effects and is currently being investigated in the development of novel immunosuppressants
Be aware
CANNABIS OESTROGENS – ETHINYLESTRADIOL
Unpredictable changes in plasma concentration. Risk of toxicity or therapeutic failure, particularly of drugs with a narrow therapeutic index
Induction or inhibition of CYP3A4mediated metabolism by cannabis. It is not yet known whether the effects are dependent on the degree of cannabis consumption
Be aware. Watch for signs of toxicity, especially when cannabis use abruptly changes
CANNABIS PHOSPHODIESTERASE TYPE 5 INHIBITORS – SILDENAFIL
Report of myocardial infarction Both drugs have been independently linked to myocardial infarction. However, the exact mechanism is uncertain
Be aware
CANNABIS PROGESTOGENS Unpredictable changes in plasma concentration. Risk of toxicity or therapeutic failure, particularly of drugs with a narrow therapeutic index
Induction or inhibition of CYP3A4mediated metabolism by cannabis. It is not yet known whether the effects are dependent on the degree of cannabis consumption
Be aware. Watch for signs of toxicity, especially when cannabis use abruptly changes
