Combantrin is taken as a single oral dose based on your body weight, at 11 milligrams per kilogram, up to a maximum of 1 gram. For most adults, that means one dose now and a second dose two weeks later. No fasting, special diet, or laxatives are needed. You can take it with or without food.
How the Dose Is Calculated
The active ingredient in Combantrin is pyrantel, and the standard adult dose is 11 mg per kilogram of body weight (or 5 mg per pound). So a 70 kg adult would take roughly 770 mg, while someone at 90 kg would take about 990 mg. The absolute ceiling is 1 gram per dose regardless of how much you weigh.
Combantrin comes in several forms: oral suspension (liquid), tablets, and chocolate squares. Each product lists the amount of pyrantel per tablet, square, or measured dose on the packaging, along with a weight-based chart. Match your weight to the chart and take the corresponding number of tablets or millilitres. If you fall between two weight brackets, use the lower one rather than rounding up.
Combantrin vs. Combantrin-1
These are different products with different active ingredients, and the dosing is not the same. Standard Combantrin contains pyrantel and is dosed by body weight as described above. Combantrin-1 contains mebendazole instead, and the dosing is simpler: one chocolate square (100 mg) as a single dose for threadworm, regardless of weight. For roundworm, whipworm, or hookworm, Combantrin-1 is taken as one square twice daily for three consecutive days.
Check which product you actually have before taking it. The boxes look similar, but the instructions differ significantly.
Why You Need a Second Dose
Pyrantel works by paralysing live worms. It triggers a kind of muscle lockup in the parasites so they lose their grip on the intestinal wall and pass out of your body in your stool. What it cannot do is kill eggs that are already laid. Those eggs can hatch into new worms in the days after your first dose.
This is why a second dose two weeks later is essential. By that point, any eggs present during the first treatment will have hatched into juvenile worms that are now vulnerable to the medication. Skipping the second dose is the most common reason people end up reinfected shortly after treatment.
What to Expect After Taking It
Most adults tolerate Combantrin well. The most commonly reported side effects are mild stomach pain, bloating, wind, and loose stools. These typically resolve within a day or two. Some people notice nausea or a brief headache. You do not need to take the day off work or change your routine.
You probably will not see worms in your stool, though it is possible. The paralysed worms are often digested before they pass, so their absence in the toilet does not mean the medication failed.
Tips to Prevent Reinfection
Threadworm (pinworm) eggs survive on surfaces for up to two weeks, which makes reinfection frustratingly easy. A few practical steps make a real difference during the treatment window:
- Treat the whole household at once. Pinworm spreads silently. Family members can carry the infection without symptoms, so everyone over the age of two should take the medication on the same day.
- Wash bedding and towels in hot water on the morning of each dose. This removes eggs shed overnight.
- Shower in the morning rather than at night. Pinworms lay eggs around the anus during sleep, and a morning shower washes them away before your hands can transfer them.
- Keep fingernails short and avoid nail-biting. Eggs trapped under nails are the primary route of reinfection.
- Avoid shaking out bedding or clothing, which can scatter microscopic eggs into the air.
Pregnancy and Breastfeeding
Pyrantel has not been formally assigned a pregnancy risk category in the United States. Animal studies have not shown evidence of harm to a developing fetus, but controlled human data are lacking. Australian guidelines classify it as category B2, meaning limited human data exists but no increased risk has been observed so far. If you are pregnant, the general guidance is to use it only when clearly needed and after weighing the benefit against the uncertainty.
For breastfeeding, pyrantel is poorly absorbed from the gut into the bloodstream, which makes it unlikely to pass into breast milk in meaningful amounts. Safety during breastfeeding has not been formally established, but most experts consider use acceptable given its minimal systemic absorption.
Which Worms Combantrin Treats
Standard Combantrin (pyrantel) is effective against threadworm (pinworm), roundworm, and hookworm. It is the go-to over-the-counter option for threadworm in most countries where it is sold. For whipworm, mebendazole-based products like Combantrin-1 are generally preferred, as pyrantel has limited activity against that species.
If you are unsure which type of worm you are dealing with, threadworm is by far the most common in adults in developed countries. The hallmark symptom is intense itching around the anus, especially at night. If your symptoms do not resolve after completing both doses, or if you notice worms that look different from the small, white, thread-like pinworms, it is worth getting a stool test to identify the parasite before trying another round of treatment.