mirtazapine and weed

Does cannabis interact with antidepressants or lithium?

Cannabis and antidepressants

Cannabis or marijuana can interact with tricyclic antidepressants (TCAs), such as amitriptyline, imipramine and dothiepin.

Both cannabis and TCAs can cause an abnormally fast heartbeat (tachycardia) and high blood pressure (hypertension). There’s also a risk of other side effects, such as confusion, restlessness, mood swings and hallucinations.

There’s a risk that using cannabis while you’re on any of these medicines could lead to problems such as tachycardia, even if you don’t already have a heart condition.

Little research has been done into the interaction of cannabis with other types of antidepressants, such as SSRIs.

Cannabis and lithium

Lithium is used to treat bipolar disorder, a condition where people can switch between depression and extreme excitement and agitation (mania).

There’s little evidence to suggest that people who use cannabis should normally not take lithium, but this hasn’t been properly researched.

Side effects of cannabis

It’s not clear how often cannabis itself can cause anxiety or depression, but research suggests this can happen.

It’s therefore recommended that if you’re anxious or depressed and you use cannabis regularly, you should try giving up and see if that helps.

Tachycardia, dizziness, anxiety, drowsiness, nausea and vomiting, difficulty sleeping and confusion are all possible side effects of cannabis.

These side effects can also be caused by certain antidepressants, so using cannabis at the same time can make them worse.

Getting advice

If you have any concerns about the medicines you’re taking, talk to your GP or pharmacist.

You can also phone NHS 111 or Talk to Frank, a friendly confidential drugs helpline, on 0300 123 6600.

Further information:

  • Antidepressant drugs
  • Can I drink alcohol if I’m taking antidepressants?
  • Depression
  • Medicines information

Page last reviewed: 27 March 2018
Next review due: 27 March 2021

Cannabis or marijuana is usually smoked and typically mixed with tobacco. It can interact with certain types of antidepressants, such as tricyclic antidepressants (TCAs), which share similar side effects.


Medically reviewed by Last updated on Sep 5, 2020.

  • Overview
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  • Professional
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Dosage Forms

Excipient information presented when available (limited, particularly for generics); consult specific product labeling. [DSC] = Discontinued product

Remeron: 15 mg [DSC] [scored]

Remeron: 15 mg [scored; contains corn starch]

Remeron: 30 mg [DSC] [scored]

Remeron: 30 mg [scored; contains corn starch]

Remeron: 45 mg [DSC]

Generic: 7.5 mg, 15 mg, 30 mg, 45 mg

Tablet Disintegrating, Oral:

Remeron SolTab: 15 mg, 30 mg, 45 mg [contains aspartame]

Generic: 15 mg, 30 mg, 45 mg

Brand Names: U.S.

  • Remeron
  • Remeron SolTab

Pharmacologic Category

  • Antidepressant, Alpha-2 Antagonist


Mirtazapine is a tetracyclic antidepressant that works by its central presynaptic alpha2-adrenergic antagonist effects, which results in increased release of norepinephrine and serotonin. It is also a potent antagonist of 5-HT2 and 5-HT3 serotonin receptors and H1 histamine receptors and a moderate peripheral alpha1-adrenergic and muscarinic antagonist; it does not inhibit the reuptake of norepinephrine or serotonin.


Rapid and complete


Extensively hepatic via CYP1A2, 2D6, 3A4 and via demethylation and hydroxylation


Urine (75%) and feces (15%) as metabolites

Onset of Action

Anxiety disorders (panic disorder): Initial effects may be observed within 2 weeks of treatment, with continued improvements through 4 to 6 weeks (WFSBP [Bandelow 2012]); some experts suggest up to 12 weeks of treatment may be necessary for response (BAP [Baldwin 2014]; Katzman 2014; WFSBP [Bandelow 2012]).

Depression: Initial effects may be observed within 1 to 2 weeks of treatment, with continued improvements through 4 to 6 weeks (Papakostas 2006; Posternak 2005; Szegedi 2009).

Time to Peak

Half-Life Elimination

20 to 40 hours; increased with renal or hepatic impairment.

Protein Binding

Special Populations: Renal Function Impairment

Clearance is reduced

30% in patients with moderate (GFR 11 to 39 mL/minute/1.73 m 2 ) and

50% in patients with severe (GFR 2 ) kidney impairment.

Special Populations: Hepatic Function Impairment

Clearance decreased by 33% and half-life and serum concentration increased by 39% and 55%, respectively, following a single dose of mirtazapine in elderly patients with mild or moderate hepatic impairment (Mauri 2014).

Special Populations: Elderly

Clearance is reduced 40% in elderly men and 10% in elderly women.

Special Populations: Gender

Women have a longer elimination half-life (37 hours) than men (26 hours).

Use: Labeled Indications

Major depressive disorder (unipolar): Treatment of unipolar major depressive disorder (MDD)

Off Label Uses

Headache, chronic tension-type, prophylaxis

Data from a limited number of patients studied suggest that mirtazapine may be beneficial for the prophylaxis of chronic tension-type headache [Bendtsen 2004] .

Based on the EFNS guideline on the treatment of tension-type headache, mirtazapine is probably effective and a second-line option for the prophylaxis of chronic tension-type headache.

Panic disorder

Data from a limited number of patients studied suggest that mirtazapine may be beneficial for the treatment of panic disorder [Boshuisen 2001] , [Carli 2002] , [Montanes-Rada 2005] , [Ribeiro 2001] , [Sarchiapone 2003] .


Hypersensitivity to mirtazapine or any component of the formulation; use of monoamine oxidase inhibitors (MAOIs) including linezolid or methylene blue IV (concurrently or within 14 days of stopping an MAOI).

Dosing: Adult

Headache, chronic tension-type, prophylaxis (alternative agent) (off-label use): Oral: Initial: 15 mg once daily at bedtime; may increase after 1 week to 30 mg/day based on response and tolerability (Bendtsen 2004)

Major depressive disorder (unipolar): Oral: Initial: 15 mg once daily at bedtime; increase dose in 15 mg increments at intervals no less than every 1 to 2 weeks based on response and tolerability. Maximum dose: 45 mg/day (product labeling); however, doses up to 60 mg/day have been used in clinical trials (VA/DoD 2016; Watanabe 2011).

Panic disorder (alternative agent) (off-label use):

Note: As monotherapy or adjunctive therapy in patients nonresponsive to SSRIs.

Oral: Initial: 15 mg once daily at bedtime; may increase in increments of 15 mg at intervals of no less than 1 week based on response and tolerability, up to a usual maximum of 45 mg once daily (product labeling). Average doses in clinical trials were

30 mg/day; doses up to 60 mg/day have been evaluated (Boshuisen 2001; Montañés-Rada 2005; Ribeiro 2001).

Discontinuation of therapy: When discontinuing antidepressant treatment that has lasted for >3 weeks, gradually taper the dose (eg, over 2 to 4 weeks) to minimize withdrawal symptoms and detect reemerging symptoms (APA 2010; WFSBP [Bauer 2015]). Reasons for a slower taper (eg, over 4 weeks) include use of a drug with a half-life 6 months) may benefit from tapering over >3 months (WFSBP [Bauer 2015]). Evidence supporting ideal taper rates is limited (Shelton 2001; WFSBP [Bauer 2015]).

Switching antidepressants: Evidence for ideal antidepressant switching strategies is limited; strategies include cross-titration (gradually discontinuing the first antidepressant while at the same time gradually increasing the new antidepressant) and direct switch (abruptly discontinuing the first antidepressant and then starting the new antidepressant at an equivalent dose or lower dose and increasing it gradually). Cross-titration (eg, over 1 to 4 weeks depending upon sensitivity to discontinuation symptoms and adverse effects) is standard for most switches, but is contraindicated when switching to or from an MAOI. A direct switch may be an appropriate approach when switching to another agent in the same or similar class (eg, when switching between two SSRIs), when the antidepressant to be discontinued has been used for 10%:

Gastrointestinal: Constipation (13%), increased appetite (17%), xerostomia (25%)

Nervous system: Drowsiness (54%)

Cardiovascular: Edema (1%), hypertension, peripheral edema (2%), vasodilation

Dermatologic: Pruritus, skin rash

Endocrine & metabolic: Increased serum triglycerides (6%), increased thirst

Gastrointestinal: Abdominal pain, anorexia, vomiting

Genitourinary: Urinary frequency (2%), urinary tract infection

Hepatic: Increased serum alanine aminotransferase (≥3 times ULN: 2%)

Nervous system: Abnormal dreams (4%), abnormality in thinking (3%), agitation, amnesia, anxiety, apathy, confusion (2%), dizziness (7%), hypoesthesia, malaise, myasthenia, paresthesia, twitching, vertigo

Neuromuscular & skeletal: Arthralgia, asthenia (8%), back pain (2%), hyperkinetic muscle activity, hypokinesia, myalgia (2%), tremor (2%)

Respiratory: Dyspnea (1%), flu-like symptoms (5%)

Frequency not defined: Cardiovascular: Orthostatic hypotension

Professional guide for Mirtazapine. Includes: pharmacology, pharmacokinetics, contraindications, interactions and adverse reactions.