There are several effective modes of intaking cannabis medicines, some being more effective than others, and some more preferable for the onset effect that the mode of delivery provides.
Dry flower cannabis is the whole flower of the cannabis plant, which clinically should only be inhaled using a vaporizer device that provides temperature control. Dry flower cannabis should not be smoked, as this caused respiratory damage and is potentially carcinogenic. This form of administration will have a fast onset and shorter duration of effect
Oral mucosal sprays are another common mode of administration, and essentially offer a mediated option between ingestion and inhalation. Forms of this mode will currently be manufactured cannabis drugs, the aerosolization of which can improve delivery over that of ingested oils, speeding onset but providing longer duration than vapour inhalation.
Taken in drops, cannabis oils are a very common form of ingesting cannabis medicines, but are perhaps less effective than some modes of administration due to first pass metabolism. Oils are still an effective option for gastrointestinal conditions, and are usually the mode of administration for eplieptic conditions in the form of Epidiolex and other patented cannabis medicines. Ingestion will generally provide a slower onset and longer duration than inhaled modes.
Topical cannabis treatments are currently the more limited form of administering cannabis medicine, and are only effective for dermatological applications and perhaps some subcutaneous treatments. Cannabis is not effectively absorbed through the skin for treatment of internal conditions.
Capsules are essentially cannabis oils delivered in a soluble casing to allow for slower release of the medicines, slowing onset but also increasing duration.