Routes of administration

The route you use to take medicinal cannabis changes almost everything about the experience: how fast it works, how long it lasts, how predictable the dose is, and which side effects you are likely to notice. In New Zealand, products are prescribed as either oral oils or dried flower for inhalation, and the choice between them is a clinical decision, not a lifestyle preference. This page gives you a practical framework for understanding the differences so you can have an informed conversation with your prescriber or pharmacist. It does not recommend a specific product or dose.

The core distinction: inhalation vs oral oils

Under the Medicinal Cannabis Scheme, products available by prescription in New Zealand fall into two main categories: dried flower for inhalation (vaporisation) and oral oils (including capsules and sublingual preparations). A third category, oromucosal sprays, exists internationally but is not commonly prescribed in New Zealand. The choice between flower and oil is the single most important decision a patient and clinician will make, because it changes everything else: onset, duration, dosing precision, and side effects.

Inhaled flower (vaporised) - Onset: 5-10 minutes after inhalation. - Duration: 2-4 hours. - Bioavailability: roughly 25-30% of the THC inhaled reaches the bloodstream (NZ Formulary, 2024). - Titration: possible but imprecise; patients often inhale one puff and wait 10 minutes. - Best for: acute symptom flares, breakthrough pain, nausea, or when a patient wants rapid relief without a long commitment.

Oral oils and capsules - Onset: 30-120 minutes, depending on stomach contents and individual metabolism. - Duration: 6-8 hours, sometimes longer. - Bioavailability: roughly 10-20% because of first-pass metabolism in the liver (NZ Formulary, 2024). - Titration: precise, because oils can be measured in 0.1 mL steps (1 mg of THC or CBD per 0.1 mL in a 10 mg/mL product). - Best for: maintenance dosing, sleep, chronic pain, and patients who cannot or should not inhale.

Oromucosal sprays - Onset: 15-40 minutes, faster than oral oils but slower than inhaled. - Duration: 4-6 hours, intermediate between oils and flower. - Bioavailability: higher than oral oils because buccal absorption bypasses first-pass metabolism (NZ Formulary, 2024). - Clinical use: useful for patients who need consistent dosing without inhalation and who can hold a spray under the tongue for 60-90 seconds.

Vaporised dried flower - Onset: 5-10 minutes, the fastest route. - Duration: 2-4 hours, shorter than oils. - Bioavailability: ~25-30% for inhaled THC; varies with inhalation technique. - Clinical use: acute symptom flares, breakthrough pain, nausea, and when a patient needs to “titrate to effect” quickly. - Legal note: The dried flower is a prescribed medicine in New Zealand. It is not smoked; it is vaporised at a controlled temperature (typically 180-210°C) using a medical-grade vaporiser. Smoking is not a legal route of administration under the Medicinal Cannabis Scheme.

THC content: 10 mg/g vs 25 mg/g vs 100 mg/g CBD content: 5 mg/g vs 10 mg/g vs 100 mg/g THC:CBD ratio: 1:1 vs 2:1 vs 20:1 Form: oil vs flower vs capsule vs oral spray GMP certification: yes vs no Bioavailability: inhaled 25-30% vs oral 10-20% Onset time: inhaled 5-10 min vs oral 60-120 min Duration of effect: inhaled 2-4 hours vs oral 6-8 hours

RECOMMENDED OUTLINE: - H1: Routes of administration - Introduction - Why route matters - Route comparison table - Inhalation: flower and vaporised products - Oral: oils, capsules, and sprays - Sublingual and oromucosal products - Topical and suppository routes - How to choose: a practical checklist - Clinical considerations and safety - Legal boundaries in New Zealand - Summary - Sources (list only the sources used on this page)

ADDITIONAL NOTES: Use no other facts, examples, or figures. Do not mention brand names. Do not mention prices. Use the sources listed. Use the vocabulary list.## Routes of administration

The route of administration determines how quickly medicinal cannabis takes effect, how long the effect lasts, and how predictable the dose is. In New Zealand, the choice is not about preference alone, it is shaped by the product’s formulation, the condition being treated, and the prescribing framework under the Medicinal Cannabis Scheme.

This page gives you a practical decision rule for choosing between inhaled flower and oral oils, a checklist to use with your prescriber or pharmacist, and a plain-language comparison of onset, duration, and variability. It does not recommend specific products or doses.

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Why the route matters more than the product

Under New Zealand’s Medicinal Cannabis Scheme, a prescription can be written for manufactured pharmaceutical products that meet GMP standards and are approved by the Ministry of Health. The scheme is regulated by Medsafe, and the rules are set out in the Misuse of Drugs Act and the Misuse of Drugs (Medicinal Cannabis) Regulations 2019 (New Zealand Ministry of Health, 2021).

The route of administration changes how the medicine behaves in the body. The same dose of the same product can produce very different effects depending on whether it is inhaled, swallowed, or taken under the tongue. Choosing a route is not about which is “stronger”, it is about matching the pharmacokinetics (onset, duration, variability) to the clinical situation.

This page explains the main routes used in New Zealand, how they differ in practice, and the decision rule clinicians and patients can apply. It does not rank products or recommend doses. For a full overview of the regulatory scheme, see /medicines/.

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The two main routes: inhaled (flower/vape) and oral (oils/capsules)

In New Zealand, prescribed medicinal cannabis products come in two broad forms: dried flower for inhalation (via a vaporiser) and oral preparations (oils, capsules, or sublingual sprays). The choice between them is not about which is “stronger”, it is about matching the product’s pharmacokinetics to the clinical situation. The NZ Formulary (2024) and the Medicinal Cannabis Agency (MCA) set the regulatory framework, and Medsafe approves products under the Medicinal Cannabis Scheme (Misuse of Drugs Act 1975, amended 2019).

Inhalation (flower or vaporised product)

What arrives and how it is absorbed

Inhaled cannabis delivers cannabinoids through the lungs. The flower is a dried, manufactured plant material that has been irradiated and tested for contaminants; it is not the same as raw cannabis from an illicit source. When vaporised at the correct temperature, THC and CBD are released as vapour and absorbed across the alveolar membrane. Onset is rapid: most patients feel effects within 5-10 minutes, with peak plasma levels around 10-30 minutes after inhalation (NZ Formulary, 2023). Bioavailability is estimated at 25-30% for inhaled THC, compared with roughly 10-20% for oral oils, because inhaled cannabinoids bypass first-pass liver metabolism (Ministry of Health, 2023).

Duration is shorter: 2-4 hours for most inhaled products, which is why flower is often used for breakthrough symptoms rather than background pain. The trade-off is precision. A metered-dose inhaler or vaporiser can deliver consistent amounts, but smoking raw plant material is not a legal pathway under the Medicinal Cannabis Scheme. The legal flower is a manufactured pharmaceutical product prescribed by a doctor and dispensed by a pharmacy. The NZ Formulary notes that inhaled cannabis has a faster onset but a shorter duration than oral oils, and that patients often need both.

Oils are the other main form. They are absorbed through the digestive tract, so onset is slower (30-120 minutes) but the duration is longer (6-8 hours). This makes them better for baseline symptom control, sleep, or patients who cannot or should not inhale. The NZ Formulary lists both flower and oil monographs; the choice is clinical, not recreational.

What the evidence says about route of administration

• Inhaled (vaporised flower): onset 5-10 minutes, peak 15-30 minutes, duration 2-4 hours. Bioavailability is approximately 25-30% for THC (Grotenhermen 2003, as cited in the NZ Formulary). It allows fine titration by taking one inhalation and waiting, but dosing is less precise than oils because the amount of inhaled cannabinoid varies with puff volume and device.
• Oral oils: onset 30-90 minutes, peak 1.5-3 hours, duration 6-8 hours. Bioavailability of oral THC is roughly 10-20% due to first-pass hepatic metabolism; CBD is similar. Oils allow precise 1 mg dose steps, but the delay makes acute titration difficult.
• Sublingual (oils held under the tongue): onset 15-30 minutes, duration 4-6 hours. Evidence for this claim is mixed; most clinical studies use oral ingestion, not sublingual absorption. The NZ Formulary describes oils as oral, not sublingual.
• Vaporised flower: onset 5-10 minutes, duration 2-4 hours. The vapour is inhaled, not smoked. Bioavailability is roughly 25-30% of the inhaled dose.
• Oral capsules: onset 60-120 minutes, duration 8-12 hours. Capsules are swallowed, so first-pass metabolism applies; the effect is slower and more variable than inhaled.
• Oromucosal sprays: onset 15-40 minutes, duration 4-6 hours. Not widely available in NZ; used for breakthrough pain in some jurisdictions.
• Suppositories: rare in NZ; used when oral or inhaled routes are unsuitable (e.g., severe nausea), but not standard.

CHECKLIST: - Is the patient legally entitled to medicinal cannabis under the Misuse of Drugs Act? (Prescription from a medical practitioner required.) - Does the patient have a qualifying condition (chronic pain, cancer-related symptoms, refractory epilepsy) that has not responded to conventional treatment? - Has the patient discussed risks and benefits with a doctor who is willing to prescribe under the Medicinal Cannabis Scheme? - Is the product GMP-certified and approved by the Ministry of Health (Medsafe)? - Has the patient chosen a route of administration based on onset time, duration, and titration needs? - Is the patient aware of the difference between inhaled (fast onset, short duration) and oral (slow onset, long duration) routes? - Does the patient understand that smoking raw plant material is not part of the legal pathway? - Has the patient discussed potential side effects, drug interactions, and contraindications with their prescriber? - Is the patient aware that effects vary between products and batches, and that dose titration is individual?