Making RSO suppositories involves melting a fat-based carrier, mixing in your RSO, and pouring the blend into molds to set. The process takes about 30 minutes of active work, and the results can be stored in your freezer for months. The key variables are choosing the right base, getting your temperatures right, and dosing each suppository consistently.
Why Suppositories as a Delivery Method
Rectal absorption of THC bypasses much of the liver’s first-pass metabolism, which is the process that breaks down cannabinoids before they reach your bloodstream when you swallow them. A pilot study on THC formulations found that oral dosing was only 25 to 50% as effective as rectal delivery, with oral bioavailability ranging from 45 to 53% relative to the rectal route. In practical terms, this means a suppository can deliver more of the active compounds from a smaller amount of RSO compared to eating the same dose.
This route also avoids the digestive system entirely, which matters for people dealing with nausea, difficulty swallowing, or gastrointestinal issues that make oral dosing unreliable.
Choosing a Base
Your suppository base needs to be solid at room temperature but melt at body temperature. The two most common options are cocoa butter and coconut oil, and each behaves differently.
Cocoa butter is the traditional pharmaceutical choice. It’s a hard solid below 25°C (77°F) and melts between 30 and 35°C (86 to 95°F), right at body temperature. The critical rule with cocoa butter: never heat it above 35°C. If you overheat it, the fat crystals rearrange into an unstable form that melts at room temperature, and your finished suppositories will be soft, greasy, and unusable. This means you need to melt it gently using a water bath, not direct heat.
Coconut oil is more forgiving. Hydrogenated coconut oil products designed for suppositories have melting points in the 33 to 40°C range and don’t have the same overheating problem. Regular unrefined coconut oil melts around 24°C (76°F), which is a bit low. If you go the coconut oil route, look for refined or fractionated versions, or simply plan to store your finished suppositories in the freezer. Many people use plain coconut oil successfully and just keep them cold until use.
Equipment You Need
Suppository molds come in two main types. Reusable plastic or silicone molds are widely available online in sizes from 1 to 5 grams per cavity, typically with 6 to 12 cavities per mold. The standard rectal suppository size is about 2 grams (roughly 2 mL). Aluminum molds from pharmaceutical suppliers are more precise, with cavity sizes from 1 to 2.5 grams, but they’re overkill for home use.
Beyond the mold, you’ll need:
- A small heat-safe container (a glass measuring cup works well)
- A pot for a double boiler setup
- A stirring utensil
- A syringe or dropper for filling molds evenly
- A kitchen thermometer if using cocoa butter
Clean everything thoroughly with hot soapy water before you start. You’re making something that goes inside your body, so treat this like food prep at minimum.
Calculating Your Dose
Before you start melting anything, figure out how much RSO goes into each suppository. RSO is a full-spectrum cannabis extract that typically contains 60 to 90% THC (or CBD, depending on the source material). A standard 1-gram syringe of RSO at 70% THC contains roughly 700 mg of THC total.
If you want each suppository to contain 25 mg of THC and your syringe is 70% THC, you’d need about 36 mg of RSO per suppository (25 divided by 0.70). From a 1-gram syringe, that gives you roughly 27 suppositories. If you’re making a batch of 12 using 2-gram molds, you’d use about 430 mg of RSO (12 x 36 mg) mixed into roughly 24 grams of base.
If you’re new to suppositories, start with a lower dose per unit, around 10 to 15 mg of THC, and adjust from there. Rectal absorption is more efficient than oral, so your usual edible dose is not the right starting point.
Step-by-Step Process
Melt the Base
Set up a double boiler by placing your glass container in a pot with an inch or two of simmering water. Add your measured amount of cocoa butter or coconut oil. If using cocoa butter, monitor the temperature carefully and pull it off heat as soon as it liquefies, keeping it below 35°C (95°F). Coconut oil is less fussy, but there’s no reason to get it screaming hot either. Aim for just above its melting point.
Mix in the RSO
RSO is extremely thick and sticky at room temperature. Warming the syringe briefly under hot running water or between your hands makes it much easier to dispense. Squeeze the measured amount of RSO directly into the melted base and stir thoroughly for two to three minutes. RSO is oil-soluble, so it blends readily into fat. The goal is a completely uniform mixture with no visible streaks or dark clumps, because uneven mixing means inconsistent dosing from one suppository to the next.
Pour Into Molds
Using a syringe or small measuring spoon, fill each mold cavity evenly. Work relatively quickly, especially with cocoa butter, as it begins to set fast once it drops below its melting range. If the mixture starts to solidify before you’ve filled all the cavities, return it briefly to the water bath. Slightly overfill each cavity rather than underfill. You can trim any excess once they’ve hardened.
Set and Store
Place the filled mold in the freezer for 20 to 30 minutes until the suppositories are completely solid. Pop them out of the mold and transfer them to an airtight container or individually wrap them in small pieces of parchment paper or plastic wrap. Store the batch in the freezer.
Storage and Shelf Life
Frozen suppositories keep for several months. The shelf life is largely determined by the freshness of your carrier oil rather than the RSO itself, since cannabinoids are quite stable when protected from light, heat, and air. Keep them in an opaque, sealed container in the freezer.
About 30 minutes before you plan to use one, move it to the refrigerator to soften slightly. You want it firm enough to handle but not rock-hard. Placing it on a paper towel on a plate prevents any condensation from making it slippery. If it’s too soft to insert comfortably, put it back in the freezer for a few minutes.
Tips for Better Results
Adding a small amount of liquid lecithin (about half a teaspoon per batch) can help the RSO emulsify more evenly into the fat base. This isn’t strictly necessary, but it improves consistency, especially in larger batches where thorough mixing is harder.
If your suppositories come out with air bubbles or uneven surfaces, try tapping the mold gently on the counter after filling to release trapped air. Pouring slowly also helps.
Silicone molds designed for candy or chocolate making work perfectly fine as suppository molds if you can find ones in roughly the right size and shape. A tapered or bullet shape is easier to use than a flat-bottomed cylinder. Look for molds with individual cavities around 1.5 to 2 mL each.