Smoking cannabis – pharmacokinetics & harm reduction

TL;DR

• Bioavailability 10-35 % depending on inhalation technique (Huestis 2007).
• Onset: 5-10 min, peak ~30 min, duration 2-4 h.
• Combustion products (tar, PAHs, CO) burden the lungs.
• The single biggest European risk factor is co-smoked tobacco.

Joint vs bong vs pipe

Bong water filters some water-soluble irritants but not lipophilic tars. Pipes deliver the highest THC per hit but burn hottest. A pure joint is clearly healthier than the classic tobacco joint.

Harm reduction when smoking

Skip tobacco, don't breath-hold (>90 % THC is absorbed in the first seconds), paper filters over activated charcoal daily, keep tolerance breaks, never combine with alcohol behind the wheel.

What actually happens during combustion

The ember of a cigarette or joint reaches 600 to 900 °C. In this range, the plant material does not just burn, it pyrolyses: tar, carbon monoxide, particulate matter, and polycyclic aromatic hydrocarbons are produced. A portion of the cannabinoids is simply destroyed in the process — the amount actually absorbed when smoking is often lower than when vaporising, even though more material is used.

Pharmacokinetically, smoking is the fastest route: onset of action within seconds to a few minutes, peak after 15 to 30 minutes, subsiding over two to four hours. It is precisely this immediacy that makes dosing intuitively controllable — you feel the effect before consuming more. The price for this is the strain on the respiratory tract, which increases significantly further due to mixed tobacco consumption.

Harm reduction and legal framework in Switzerland

Those who do not want to do without inhalation reduce their risk most effectively through three points: no tobacco in the mixture, no deep holding of the smoke — absorption is complete after a few seconds, holding it longer only brings more tar — and no shared mouthpieces. Smoking in publicly accessible indoor spaces is prohibited in Switzerland under the Protection Against Second-Hand Smoke Act; cantonal regulations sometimes go further.

Swiss classification: Products with less than 1% total THC (THC + THCA × 0.877) are not narcotics and are freely available; above this, the Narcotics Act applies. For road traffic, the method of consumption is irrelevant — the decisive factor is the detection limit value of 1.5 µg THC per litre of blood, which leads to unfitness to drive. Medical cannabis has been prescribable by doctors without an exceptional permit from the BAG since August 2022.

Swiss pilot projects and legal consumption in transition

Switzerland is currently testing new approaches in cannabis policy through scientific pilot trials under the Narcotics Act (BetmG). These time-limited studies, such as in Zurich or Basel, enable registered participants to legally purchase and consume cannabis containing THC under state supervision. The BAG closely accompanies these projects to scientifically evaluate the effects on public health and consumption behavior. Strict rules apply to participants, particularly regarding transfer to third parties and consumption in public spaces, which continues to be handled restrictively.

Within these pilot projects, the smoking behaviour of participants is also recorded in order to test health prevention concepts directly in everyday life. The distributed products are subject to strict quality controls by Swiss authorities, which rules out contaminants such as pesticides or synthetic cannabinoids. Nevertheless, inhalation through combustion remains associated with health risks for the respiratory tract, even with controlled products. In the long term, the data obtained is intended to serve as a basis for decision-making for future national legislation and to objectify the debate on regulated distribution.

Physiological strain from combustion by-products

When smoking cannabis, the incomplete combustion of the plant material produces numerous gaseous and particulate pollutants that penetrate deep into the respiratory tract. In addition to tar, carbon monoxide is a major by-product that binds to haemoglobin in the blood, thereby temporarily restricting oxygen transport in the body. This leads to increased strain on the cardiovascular system, as the body has to compensate for the reduced oxygen levels by increasing the heart rate. In the long term, these combustion products irritate the mucous membranes of the bronchi and promote chronic respiratory diseases.

The health impact is further influenced by the inhalation technique, as cannabis smoke is often inhaled more deeply compared to tobacco smoke. Although the active ingredients are rapidly absorbed via the alveoli, the fine soot particles and pollutants remain in the lung tissue. In order to reduce the strain on the respiratory tract, consumers in practice increasingly resort to alternative forms of consumption or use special filter systems. Medical professionals point out that the inhalation of combustion products fundamentally represents the greatest avoidable risk in cannabis consumption.

Hygiene and maintenance of consumption utensils

The regular cleaning of smoking devices such as pipes or bongs is an often neglected aspect of harm reduction in everyday life. In damp environments, especially in the water of water pipes, biofilms of bacteria, mould, and algae form after only a short time. If these devices are used repeatedly without thorough cleaning, users inhale not only combustion products but also microbial pathogens directly into their lungs. This can promote acute respiratory infections and place a heavy strain on the respiratory immune system in addition to the thermal stimuli.

Material-friendly cleaning agents and mechanical brushes are suitable for cleaning to completely remove sticky resin residues and tar deposits. The water in bongs should be freshly filled before each use and disposed of immediately after use to prevent the growth of germs. Sharing mouthpieces on joints or pipes also poses significant risks for the transmission of pathogens such as viruses or bacteria. Consistent hygiene of the utensils protects the respiratory tract from avoidable additional strain and maintains the functionality of the devices.

Dealing with overdose and acute situations

Unexpectedly heavy consumption or a misjudgement of the potency of cannabis smoke can lead to acute symptoms of overdose. Typical symptoms of an overdose manifest as strong palpitations, dizziness, sweating, as well as acute anxiety or panic attacks. In such moments, it is crucial to find a quiet environment, take deep breaths, and drink sufficient water to stabilise the circulation. Since the effects of smoking set in very quickly, the most intense symptoms usually subside faster than with oral ingestion.

If symptoms persist or in the event of severe anxiety, professional help should be sought to rule out health risks. In Switzerland, the emergency number of Tox Info Suisse is available 24/7 at 145 for medical advice on poisoning. Companions should not leave the affected person alone and should have a calming effect on them until the effects noticeably subside. Avoiding mixed consumption with alcohol or other psychoactive substances is the most effective measure to prevent such unpredictable acute situations in advance.

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