Published: 14th November, 2025
Cannabis has medicinal value. It can be used as a medicine. It is not a medicine by default.
New Zealand has established a legacy of good regulatory policy. In 2010, Sativex®, an oromucosal spray containing THC
and CBD, classified as a Class B1 Controlled Drug, became the first approved medicinal cannabis product,1 following the
development of regulatory policy and clinical guidance. The Misuse of Drugs (Medicinal Cannabis) Regulations 2019 brought into
effect domestic production, minimum quality standards,2 and simplified prescribing and dispensing of unapproved
medicinal cannabis products in 2020.3 The supply of medicinal cannabis products has since increased markedly. The
developments in New Zealand represent a common thread in the global context. A scientific review by the World Health Organization
resulted in the UN Commission on Narcotic Drugs formally recognising the medical value of cannabis in 2020.4
The pharmacological basis of cannabis as a medicine
The pharmacological basis of the action of cannabis is well-established. The body’s endocannabinoid system is a lipid-based
cell-signalling network that modulates physiological homeostasis – regulating neurotransmission, immune activity and metabolic
processes. Endocannabinoids are lipid-based retrograde neurotransmitters that exhibit biological activities like those of
plant-derived cannabinoids. The pharmacological effects of cannabinoids are mediated through specific cannabinoid receptors. Two
types of cannabinoid receptors—CB1 and CB2—have been identified; both belong to the G-protein-coupled receptor
superfamily.5, 6
The cannabis plant (Cannabis sativa L.) produces pharmacologically active cannabinoids, principally
delta-9-tetrahydrocannabinol (THC) and cannabidiol (CBD). These phyto-cannabinoids are substrates for the cytochrome P450 enzyme
family—particularly CYP3A4, CYP2C9 and CYP2C19—which also means that there is potential for clinically significant medicine
interactions, especially in a polypharmacy context.
Therapeutic use of cannabis and clinical evidence
Medicinal cannabis is not a panacea. It is prescribed in general practice, and in pain, oncology and palliative care settings,
to manage the symptoms of various chronic conditions, often as an adjunct treatment in patients who may not have responded
adequately to other medicines.
The clinical evidence base is incomplete but is improving steadily. The most consistent and high-quality data support the use
of THC and THC:CBD formulations in addressing the affective dimensions of pain, improving appetite and sleep quality, and
treating moderate to severe spasticity in patients with multiple sclerosis. High-dose CBD has demonstrated efficacy in
reducing seizure frequency in treatment-resistant epilepsies, particularly in paediatric populations. For other proposed
indications, the evidence remains low quality or inconclusive.
While medicinal cannabis generally exhibits a favourable safety profile, transient physiological, psychological and
neurological adverse effects, such as dizziness, anxiety and cognitive impairment, are common with higher doses of products
containing THC. Treatment discontinuation is frequently linked to excessive dosing of either THC or CBD, which can amplify
adverse effects and compromise tolerability.
For further information, see
Fleisch, Woodbridge & Burgess, 2025,
sections: Current Situation, Pharmacology and Prescribing.
Translating clinical research to clinical practice
Although clinical trials involving standardised medicinal cannabis products have significantly advanced our understanding of
their safety and therapeutic potential, translating these findings into routine clinical practice remains a persistent
challenge.
The commercial landscape is currently characterised by substantial variability in dosage formats, formulations and product
specifications. This heterogeneity undermines consistency in prescribing and compromises patient outcomes. The lack of product
standardisation also limits the feasibility of robust post-market surveillance, impeding our efforts to monitor safety and
real-world effectiveness.
As a result, pharmacovigilance systems for cannabis-based treatments remain fragmented or non-functioning. Evaluation outside
of controlled trials is inconsistent, further obstructing the development of evidence-informed prescribing protocols.
The status in our region
As of October, 2025, approximately 61 medicinal cannabis products have been verified as meeting New Zealand’s minimum quality
standard under the
Medicinal Cannabis Scheme.2 While these products may be delivering clinical benefit, persistent
challenges continue to undermine the integrity of the Medicinal Cannabis Scheme. N.B. A verified product (i.e. meeting the
minimum quality standard) is not the same as an approved medicine; non-verified medicinal cannabis products are also still
able to be accessed in New Zealand.
Key concerns here are mirrored in Australia.7 These include the proliferation of dosage forms and administration
devices, non-standard medicine nomenclature (some with very inappropriate names), manufacturing quality changes between production
batches and inconsistent availability of products at the agreed quality standard. It is also important to note that a paucity of
clinical data for most products continues to hamper evidence-informed decision-making. Other potential issues include safety
concerns with high-potency THC products, particularly in vulnerable patient groups such as young people, frail elderly people and
people with mental illness. There are also concerns some prescriber communities have biases on prescribing specific products, have
an incentive or are pressured, to prescribe, and may prescribe outside the current clinical evidence base.
Indeed, in New Zealand, while the emergence of specialised cannabis clinics has expanded patient access, it has
also raised concerns about the privatisation of prescribing, the erosion of integrated care and patient co-management, and
financial conflicts of interests blurring clinical judgement.8 Researchers Rychert and Wilkins note that the
programme has resulted in a rapid increase in the supply of medicinal cannabis products, reduced prices and an expanded range
of products, in particular THC-dominant products. From 1 May, 2023, to 30 April, 2024, a total of 164,979 product units of
medicinal cannabis were prescribed in New Zealand:9, 10
- 55.6% were CBD or balanced THC:CBD products
- 45.4% were THC products (75,121 units), specifically:
- 17.7% THC-dominant flower administered by vaporisation (29,318 units)
- 21.6% THC-dominant flower administered as tea (35,757 units)
- 6.1% THC-dominant oral solutions or sprays (10,046 units)
Prescribing high-dose THC products to males aged 18 – 45 years poses a potential public health risk, given the elevated
prevalence of cannabis use disorder in this demographic. This group is already recognised as having a heightened susceptibility
to substance dependence, raising concerns about long-term safety and treatment appropriateness.11, 12
Certain dosage forms, such as cannabis ‘teas’, are particularly problematic. These formulations exhibit poor and variable
bioavailability, are often derived from lower-grade dried flower, and may be administered via inhalation, compounding potential
harm. Their inconsistent pharmacokinetics undermine therapeutic predictability and complicate clinical monitoring.
Pharmacists face persistent operational challenges in managing cannabis flower products.13 These include high-volume
Class C1 Controlled Drug storage requirements, compounded by non-standard medicine naming conventions and variable dosage formats.
Such variability impairs effective batch tracking and compromises the integrity of pharmacovigilance systems.
In New Zealand, the Section 29 pathway provides a legal mechanism for accessing unapproved medicinal cannabis products on a
named-patient basis. However, the widespread use of large volumes of unapproved products across a broad patient population raises
safety concerns, as these products have not undergone Medsafe’s full assessment for safety, efficacy and quality. Section 29 of
the Medicines Act 1981 is intended for case-by-case, practitioner-led access—not for general distribution. In this context,
adherence to the minimum quality standard, labelling and advertising requirements is paramount to safeguard patient safety and
clinical integrity.
Primary care has a pivotal role in initial patient assessment for suitability of medicinal cannabis products, ongoing management
and co-management with other specialists where appropriate. Therefore, a sound understanding of medicinal cannabis as a treatment
option is increasingly important in both care settings.
Assessing patient suitability: Initial evaluation and prescribing considerations
Patients may hold strong views on medicinal cannabis—some will arrive well-informed, while others may be unfamiliar with its
therapeutic use. Prescribers must be equipped to engage in meaningful conversation to assess whether unapproved medicinal
cannabis or an approved cannabis medicine is appropriate for the condition and the patient.
If medicinal cannabis is deemed suitable, clinicians must discuss risks, benefits and uncertainties openly with patients,
obtain informed consent and set expectations around treatment goals, duration and review.
For further information, see:
The
RNZCGP position statement on medicinal cannabis prescribing, and the patient suitability flow chart proposed by
Fleisch, Woodbridge &
Burgess, 2025.
Managing uncertainty
Prescribing and dispensing medicinal cannabis is multifaceted. The clinical trial evidence base is incomplete, particularly
for first-line use. Variability in product cannabinoid content, dosage form and bioavailability adds further complexity.
Almost all products are unapproved and are often controlled drugs containing THC. Many require administration devices (e.g.
vaporisers, syringes, sprays, droppers) and have tailored dosing schedules.
Medicinal cannabis is generally well tolerated, with dose-dependent adverse effects. However, medicine interactions may occur,
and some patients have contraindications to treatment (e.g. cardiovascular conditions, pregnancy, psychosis). Adverse effects
with high doses of CBD can result in worsened symptom control, sleepiness, abnormal liver function and diarrhoea. High doses
of THC may result in physiological, psychological and neurological symptoms such as tachycardia, anxiety, psychomotor
impairment or sedation.
Prescribing unapproved medicines or prescribing medicines off-label carries an inherent risk.14 Medical practitioners
must obtain informed consent, discuss available evidence and safety considerations and assume full responsibility for prescribing
decisions. Pharmacists, in addition to fulfilling documentation and dispensing requirements, should counsel patients on the
unapproved status of the medicine and associated risks.
The involvement of a specialist in pain medicine, oncology or palliative care is essential for managing complex cases; they can
evaluate the suitability of cannabis-based treatment in the context of concurrent medicines and the broader management plans.
Patients need to clearly understand the onset time and duration of effect, and potential adverse effects (e.g. anxiety, sedation,
impaired cognition) associated with different doses and dosage forms of medicinal cannabis. Advise patients of absolute
contraindications and precautions when using THC-containing products.
Prescribing considerations – safety, efficacy and risk mitigation
Medicinal cannabis is often a second or third-line treatment and used as an adjunct. Many patients will be co-prescribed other
medicines, therefore consider the potential for interactions and how they will be identified and managed.
Exercise caution when co-prescribing medicines:
- That interact with CYP450 enzymes (e.g. CYP3A4, CYP2C9, CYP2C19)
- With sedative effects, as THC may impair response time, co-ordination and concentration. N.B. Use with alcohol should
also be avoided.
- That affect cardiovascular function, as THC can cause a transient rise in blood pressure and heart rate
Familiarise yourself with dosage forms, dosing protocols, and titration schedules:15
- Preferentially select standardised formulations, such as oromucosal sprays, formulated oral solutions or vaporisation
capsules, over irregular preparations like loose-leaf teas, which exhibit poor bioavailability and unpredictable
pharmacokinetics
- Prioritise products with a lower-THC content (< 20% w/w or v/v), unless higher concentrations are clinically justified
and supported by titration protocols and monitoring plans
- Remain vigilant for product-associated side effects, potential adverse reactions and device-related risks (e.g. vaporiser
malfunction, mucosal irritation, dosing errors)
Pay particular attention to the following patient groups:
- Patients with cardiovascular risk factors, hepatic or renal impairment or a history of psychosis or depression—these
conditions may amplify susceptibility to adverse effects, particularly with THC-containing products
- Frail and elderly patients, who are more vulnerable to side effects such as orthostatic hypotension, sedation and
cognitive impairment
- Paediatric patients (aged < 18 years)—avoid prescribing unless clinically justified and under specialist
supervision, given developmental neurotoxicity concerns and limited safety data
- Young adult males (aged 18 – 45 years)—especially those requesting high-THC products or reporting prior substance use.
Monitor closely for signs of misuse, diversion, dose escalation or emerging dependence.
Choice of administration
Consider what dosage form would be most practical and effective for the patient. The dosage form directly affects bioavailability
and therefore the actual dose delivered. While there is no evidence that a pulmonary dose is better than an oromucosal dose, the
former offers the advantage of a more rapid onset of action and shorter active period.
Table 1. Administration method considerations. Adapted from Fleisch, Woodbridge & Burgess, 2025.15
|
Pulmonary (vapour inhalation)
|
Oromucosal (sublingual & buccal)
|
|
Onset of clinical effects
|
5 – 10 minutes
|
30 – 90 minutes
|
|
Duration
|
1 – 3 hours
|
6 – 8 hours
|
|
Positives
|
Rapid onset of action, advantageous for acute or episodic symptoms, easy to titrate to an optimal dosage
Vaporiser medical devices minimise harms from inhalation
|
Fast absorption and onset of action, long duration of action
Various dose forms – droppers, sprays, wafers
|
|
Negatives
|
Upfront expense and knowledge of the device
|
Part of the dose may be swallowed, absorbed and metabolised
A high level of dexterity is required for some devices (e.g. droppers)
|
Starting dose
As with any medicine, medicinal cannabis should be prescribed at the lowest possible dose that achieves the desired clinical
effect with minimal adverse effects. A conservative dosing protocol is recommended if there are any concerns about tolerance,
adverse effects or medicine interactions.
Key considerations:
- Pharmacological effects are dose-dependent and subject to interpatient variability
- Systemic absorption varies in timing and intensity depending on the route of administration
Table 2 provides approximate pharmacokinetic properties for THC-containing products, by route of administration. The medicine
data sheet or New Zealand Formulary (for an approved product) or product information should be consulted for product-specific
prescribing information.
Table 2. Pharmacokinetics of THC, by route of administration.
|
Route
|
Dose
|
Cmax
|
Onset
|
Duration
|
|
Inhalation vapour
|
Up to 20 mg
|
80 ng/mL16
|
5 – 10 minutes
|
1 – 3 hours
|
|
Oromucosal spray
|
5 – 15 mg
|
THC: 2 – 4 ng/mL17
11-OH-THC: 1.8 – 5.2 ng/mL
|
30 – 90 minutes
90 – 180 minutes
|
6 – 8 hours
|
N.B. Oromucosal administration results in the partial hepatic metabolism of THC and moderate 11-OH-THC formation.
The half-life of THC is 24 – 36 hours and is 12 – 24 hours for 11-OH-THC. Vaporisation devices may yield ≤ 50% of available cannabinoids
depending on device, temperature and inhalation technique.18, 19
Dose titration
Provide clear guidance to the patient on the starting dose and titration process, including how dosage adjustments will be made.
A titration period is essential to establish a personalised therapeutic dosage. Depending on the indication, start with evenly spaced
doses throughout the day, adjusted according to individual response and tolerability. Gradually increase the dose until the optimal
daily dose is reached—defined as the greatest therapeutic benefit with minimal side effects.
Principles for titration:
- Start low, go slow: dosing time and frequency depend upon the indication. Initiate with multiple small doses,
rather than a single large dose, to cumulatively reach the target dose for a therapeutic effect. Maintain a low total daily
dose during the initial phase.
- Allow time for response: maintain the same low dose and total daily dosage for several days and monitor clinical
response before adjusting
- Incremental increases: cautiously increase the dose, as required, allowing time between adjustments to assess
efficacy and tolerability
- Optimal daily dose: slow, incremental increases allow patients to reach an optimal daily dose. The treatment
protocol can then be monitored.
Monitoring
Schedule clinical reviews frequently during the early phase of treatment to assess tolerability, therapeutic response and adherence.
Identify and respond to red flags such as rapid dose escalation beyond expected titration curves, repeated early refill requests
or signs of misuse or diversion.
Collaborate with pharmacists to reinforce patient understanding of dosing protocols and administration techniques and device operation.
Pharmacists should ensure consistency between prescribing instructions and dispensing labels, and address patient uncertainty at the
point of supply.
Advise patients to pause upward titration immediately if adverse effects emerge, and to report this promptly to their clinician or
pharmacist. Report all adverse medicine events and device malfunctions to
CARM and Medsafe,
respectively. This supports continuous improvement of product quality and clinical guidance.
Cessation
The treatment plan should include agreed treatment goals and how therapeutic effect will be measured. Establish a clear plan to discontinue
or modify treatment if it proves ineffective, causes intolerable side effects or if misuse or dependence is identified. Confirm a protocol
for the return of unwanted or unused medicines, and, where applicable, the administration device.
The future of the medicinal use of cannabis depends on addressing key clinical and regulatory challenges. There is a pathway forward.
The following are actionable steps to address these issues.
Promoting the rational use of medicinal cannabis is paramount20—these are mainly unapproved products with
limited or no clinical data associated with them.
Education is necessary. It is key to rational medicine use. The uptake of clinical education contributes to reducing
variability in prescribing, dispensing and administration. The Clinical Primer on Cannabis text offers a robust foundation for safe
and effective prescribing, dispensing and administration. It is a RNZCGP-endorsed resource and is freely available at:
clinicalprimercannabis.com. The
bpacnz article on the
medicinal cannabis scheme framework provides a useful précis for health
professionals to understand the programme. A separate guide for
pharmacists is also available.
A comprehensive appraisal of available formulations, dosage formats and associated devices is needed, regularly updated
to reflect emerging clinical evidence, and made available via a central reference point. This will allow New Zealand prescribers and
pharmacists to familiarise themselves with suitable dosage forms, dosing protocols and titration schedules.
Timely and consistent enforcement of medicinal cannabis regulations is essential to reduce ambiguity and mitigate
current risks. Priority areas include dosage form standardisation, medicine nomenclature, product labelling and the regulation of
therapeutic claims. Greater uniformity across these domains will enhance the capacity of post-market surveillance systems to monitor
prescribing practices, product quality and patient safety. Such regulatory coherence is critical to sustaining the integrity and
long-term effectiveness of the Medicinal Cannabis Scheme.
