Guanfacine

For an informed discussion with your doctor or pharmacist. This information collection is not a clinically validated interaction checker. Missing data do not establish safety. Do not change or stop prescribed medicines on the basis of this information. The findings apply to the specific conditions studied; laboratory and animal studies cannot be directly extrapolated to humans.

Active substance: Guanfacine

Examples of brand names: Intuniv [EU/DE]

ATC code: C02AC02

Main use (for orientation): ADHD; hypertension

Documented research summary

Controlled guanfacine–THC study 28641496: certain attention/memory effects, but no protection concerning subjective effects/heart rate. Guanfacine withdrawal study 29659126, n=15, reduces withdrawal irritability/sleep disturbance, not cannabis self-administration. No pharmacokinetic evidence.

Uncertainties and limitations

PMC6191371 full text inaccessible; abstract-based. Do not extrapolate acute/short studies to long-term combination safety. Documented individual title/abstract assessment with selected relevant full texts; not an exhaustive worldwide systematic review or independent human specialist approval. Missing data do not establish safety. All 28 cannabinoids are within the search scope, not 28 clinically investigated pairs per drug.

Separately recorded findings

2 separately recorded findings. Each statement applies to its documented study context.

THC – clinically investigated

Finding ID: B0489

Type of result: Context-specific finding

Observation: Guanfacine improved spatial-memory/omission endpoints; subjective THC effects and heart rate did not change correspondingly.

Mechanism: α2A agonism modifies selected cognitive THC effects.

Study type: Controlled human THC challenge, pharmacodynamics

Context studied: Guanfacine 3 mg for six days versus placebo before THC 20 mg; original abstract.

Clinical interpretation: Human endpoint directly studied under narrowly defined study conditions; long-term safety and generalisability not established.

Limitations and uncertainties: Small experimental acute context, not general protection against cannabis effects or clinical ADHD combination safety.

Original sources for this finding: Guanfacine Attenuates Adverse Effects of Dronabinol (THC) on Working Memory in Adolescent-Onset Heavy Cannabis Users: A Pilot Study. [VF_P_28641496]

Cannabis; standardised smoking/abstinence phases – insufficient evidence

Finding ID: B0490

Type of result: Withdrawal model, not an isolated acute pair assessment

Observation: Guanfacine reduced irritability and sleep problems during cannabis abstinence, not cannabis self-administration.

Mechanism: α2A agonism influences withdrawal symptoms.

Study type: Small controlled human laboratory model

Context studied: 15 people, two nine-day phases; immediate-release guanfacine 2 mg in the evening, with use, abstinence and relapse phases.

Clinical interpretation: No isolated investigation of the pair; clinical relevance as a medicine–cannabinoid interaction cannot be determined.

Limitations and uncertainties: Do not present withdrawal symptoms as a general simultaneous cannabis–guanfacine interaction or an efficacy promise.

Original sources for this finding: Guanfacine decreases symptoms of cannabis withdrawal in daily cannabis smokers. [VF_P_29659126]

References and access status

[VF_L_D0430] GUANFACINE EXTENDED-RELEASE (GUANFACINE) TABLET, EXTENDED RELEASE [REMEDYREPACK INC.]

Original source / bibliographic reference

Authors: Marketing authorisation holder; official product information via DailyMed

Year: 2026

Source type: Official medicine information; relevant identity, PK, PD and DDI sections read individually

Source access – 23 October 2026: Source destination was accessible when checked.

Bibliographic attribution or source identity cross-checked.

[VF_P_28641496] Guanfacine Attenuates Adverse Effects of Dronabinol (THC) on Working Memory in Adolescent-Onset Heavy Cannabis Users: A Pilot Study.

Original source / bibliographic reference

Authors: Mathai DS, Holst M, Rodgman C, Haile CN, Keller J, Hussain MZ, Kosten TR, Newton TF, Verrico CD.

Year: 2018

Source type: Scientific publication; precise study type and suitability described in the finding or individual review

DOI: 10.1176/appi.neuropsych.16120328

PMID: 28641496

Source access – 23 October 2026: Direct retrieval could not be fully verified; availability remains unresolved.

Bibliographic attribution or source identity cross-checked.

DOI – publisher access (access restrictions may apply)

[VF_P_29659126] Guanfacine decreases symptoms of cannabis withdrawal in daily cannabis smokers.

Original source / bibliographic reference

Authors: Haney M, Cooper ZD, Bedi G, Herrmann E, Comer SD, Reed SC, Foltin RW, Levin FR.

Year: 2019

Source type: Scientific publication; precise study type and suitability described in the finding or individual review

DOI: 10.1111/adb.12621

PMID: 29659126

Source access – 23 October 2026: Direct retrieval could not be fully verified; availability remains unresolved.

Bibliographic attribution or source identity cross-checked.

DOI – publisher access (access restrictions may apply)

PubMed Central – full-text access according to the literature database – Archive attribution confirmed by Europe PMC metadata. Direct retrieval was not fully verified here; access may require a browser check.

Europe PMC – full-text access according to the literature database – Listed as freely available HTML full text in the official Europe PMC metadata. Direct retrieval was not fully verified here.

Research as of 23 October 2026. Not all original full texts could be reviewed in full. Source accessibility and the strength of scientific evidence must be assessed separately. An accessible link does not establish medical approval; a bibliographic record with an abstract does not replace the original full text.

Drug search and explanation of the evidence · Guide: cannabinoids and medicines · Author and responsibility