Routes of administration

The route you use to take medicinal cannabis changes 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 vaporisation, and the choice between them is a clinical decision, not a lifestyle preference. The material below 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 route of administration changes how the medicine behaves in the body. The same dose of the same formulation 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, how long effects last, variability) to the clinical situation.

Why the route matters more than the product

Under New Zealand’s Medicinal Cannabis Scheme, a prescription can be written for manufactured pharmaceutical items 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 sections below explain 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 items or recommend doses. For a full overview of the regulatory scheme, see /medicines/.

The two main routes of administration

In New Zealand, prescribed medicinal cannabis comes in two broad forms: dried flower for vaporisation and oral preparations (oils, capsules, or sublingual sprays). The choice between them matches 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 items under the Medicinal Cannabis Scheme (Misuse of Drugs Act 1975, amended 2019).

Vaporised dried flower

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 heated at the correct temperature in a medical-grade device, 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 the first draw (NZ Formulary, 2023). Bioavailability is estimated at 25-30% for THC taken this way, compared with roughly 10-20% for oral oils, because inhaled cannabinoids bypass first-pass liver metabolism (Ministry of Health, 2023).

Effects are shorter: 2-4 hours for most flower used this way, which is why it is often used for breakthrough symptoms rather than background pain. The trade-off is precision. A metered-dose device 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 item prescribed by a doctor and dispensed by a pharmacy.

Legal note: Dried flower is a prescribed medicine in New Zealand. It is not smoked; it is heated at a controlled temperature using a medical-grade vaporiser. Smoking is not a legal route of administration under the Medicinal Cannabis Scheme.

Oral oils and capsules

Oils are absorbed through the digestive tract, so onset is slower (30-120 minutes) but effects last longer (6-8 hours). This makes them better for baseline symptom control, sleep, or patients who cannot or should not inhale vapour. Capsules follow the same digestive pathway, with an onset of 60-120 minutes and a period of action that can reach 8-12 hours.

Titration advantage: 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), giving precise control over the dose. The delay in feeling effects makes acute titration difficult, so oils suit maintenance dosing rather than rapid relief.

Oromucosal sprays

Oromucosal sprays sit between the two main routes. Onset is 15-40 minutes, faster than oral oils but slower than inhaled flower. Effects last 4-6 hours. Bioavailability is higher than oral oils because buccal absorption bypasses first-pass metabolism (NZ Formulary, 2024). This route is useful for patients who need consistent dosing without inhaling vapour and who can hold a spray under the tongue for 60-90 seconds. Oromucosal sprays are not commonly prescribed in New Zealand.

What the evidence says about each route

• Inhaled flower: onset 5-10 minutes, peak 15-30 minutes, effects last 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 draw and waiting, but dosing is less precise than oils because the amount of cannabinoid taken in varies with puff volume and device.
• Oral oils: onset 30-90 minutes, peak 1.5-3 hours, effects last 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.
• Oral capsules: onset 60-120 minutes, effects last 8-12 hours. Capsules are swallowed, so first-pass metabolism applies; the effect is slower and more variable than inhaled flower.
• Sublingual (oils held under the tongue): onset 15-30 minutes, effects last 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.
• Oromucosal sprays: onset 15-40 minutes, effects last 4-6 hours. Not widely available in New Zealand; used for breakthrough pain in some jurisdictions.
• Suppositories: rare in New Zealand; used when oral or inhaled routes are unsuitable (for example, severe nausea), but not standard.

How to choose: a practical checklist

Use these questions with your prescriber or pharmacist to match the route to your situation.

Ask about your symptom pattern

1. Do you need relief within 10 minutes for a sudden flare, nausea, or breakthrough pain? If yes, ask whether inhaled flower fits your clinical profile.
2. Do you need steady, long-lasting background control for sleep or chronic pain? If yes, ask about oral oils or capsules.
3. Do you need something in between, faster than an oil but without inhaling vapour? Ask whether an oromucosal spray is available and suitable.

Ask about your ability to use the route safely

1. Can you use a medical-grade vaporiser correctly and consistently? If not, oils or capsules may be more reliable.
2. Do you have a respiratory condition that makes breathing in vapour a concern? If yes, prioritise oral or sublingual options.
3. Can you hold a spray under your tongue for 60-90 seconds without swallowing? If not, an oral oil may work better than a spray.

Ask about dosing precision

1. Do you need to adjust your dose in very small steps (for example, 1 mg at a time)? Oils measured with an oral syringe give you that control.
2. Do you prefer a fixed, pre-measured dose? Ask about capsules.

Ask about how long effects last

1. Will a 2-4 hour window cover your symptom, or do you need coverage that lasts through the night? Match the period of action to the task: short for acute flares, long for sleep and baseline pain.

Clinical considerations and safety

Do not drive after taking THC

THC impairs coordination, reaction time, and judgment. The NZ Formulary and the Medicinal Cannabis Agency advise patients not to drive for at least six hours after taking an oral dose and for at least four hours after inhaling. These are minimums; individual responses vary. If you are unsure, do not drive. Discuss timing with your prescriber and report any sedation or impairment.

Start low and go slow

Begin with the lowest dose your prescriber recommends. Wait long enough to feel the full effect before taking more: at least two hours for oral oils and capsules, and 10-15 minutes between draws for flower used with a vaporiser. Rushing the titration is the most common cause of an uncomfortable experience.

Storage and security

Keep all medicinal cannabis items in their original dispensed packaging, out of sight and reach of children. Store oils upright and away from heat. Dried flower must stay in its pharmacy container with the prescription label attached; carrying it loose or in an unlabelled container may breach the law.

Legal boundaries in New Zealand

Under the Medicinal Cannabis Scheme, only a doctor can prescribe these items, and only a pharmacy can dispense them. Dried flower is a prescribed medicine; it is illegal to smoke it. Possession of prescribed cannabis outside its original packaging, or use by anyone other than the named patient, remains an offence under the Misuse of Drugs Act 1975. The scheme is regulated by Medsafe and the Medicinal Cannabis Agency. For the full regulatory framework, see /medicines/.