Betapen is a phenoxymethylpenicillin suspension, 125 mg per 5 ml — penicillin V. It treats streptococcal throat infections, tonsillitis, ear infections, skin infections and dental infections, and is used long term to prevent rheumatic fever. Take it on an empty stomach and finish the course.
What is Betapen?
Betapen contains phenoxymethylpenicillin, better known as penicillin V, at 125 mg per 5 ml as a suspension — a form suited to children.
Penicillin V kills bacteria by preventing them from building their cell walls. Without that rigid outer layer the bacterium bursts. Human cells have no cell wall, which is why penicillin attacks bacteria and leaves us alone.
It is the oral form of the original penicillin, and it remains in use for a specific reason. Penicillin V is narrow-spectrum: it is very effective against streptococci and a few other organisms, and does little against anything else.
That narrowness is a genuine virtue, not a shortcoming. A targeted antibiotic disturbs less of your normal bacteria, causes fewer side effects such as thrush and diarrhoea, and applies less pressure toward antibiotic resistance. When the likely organism is Streptococcus — as in most bacterial sore throats — penicillin V is the right tool, and reaching for something broader such as amoxicillin offers no advantage.
Critically, **Group A Streptococcus has never developed resistance to penicillin.** Decades on, it still works reliably, which is why it remains first-line.
It is a Schedule 4 prescription medicine.
What is Betapen commonly used for?
Penicillin V is prescribed for:
- Streptococcal throat infection (“strep throat”) and tonsillitis — its principal use.
- Scarlet fever.
- Middle ear infection, in some cases.
- Skin infections including cellulitis and erysipelas, caused by streptococci.
- Dental infections, particularly in children.
- Preventing rheumatic fever from recurring — long-term, sometimes for years.
- Preventing infection in people without a functioning spleen, or with sickle cell disease, taken daily and long term.
Two of those deserve explanation.
Strep throat and the full course. Most sore throats are viral and need no antibiotic at all. Where a throat infection is confirmed or strongly suspected to be streptococcal, the antibiotic does more than shorten the illness — it prevents rheumatic fever, an immune reaction that can permanently damage heart valves. This remains a real problem in South Africa. The full course matters for that reason, even though the throat feels better in two or three days. Stopping early is the classic mistake.
Long-term prevention. Children who have had rheumatic fever, and people without a working spleen, take a small daily dose for years. It is preventing something serious rather than treating anything present — feeling well is the intended result, not a reason to stop.
How Betapen fits into this medicine category
| Group | Examples | Common targets |
|---|---|---|
| Narrow-spectrum penicillins | Penicillin V (Betapen) | Streptococcal throat, skin, dental |
| Anti-staphylococcal penicillins | Flucloxacillin | Skin and soft tissue — staphylococci |
| Broad-spectrum penicillins | Amoxicillin | Chest, ear, throat, sinus, urinary |
| Macrolides | Azithromycin, erythromycin | Used in penicillin allergy |
| Nitroimidazoles | Metronidazole | Anaerobic and dental infections |
If you are allergic to penicillin, a macrolide is the usual substitute. See the antibiotics and antimicrobials hub.
What to check before using Betapen
Take it on an empty stomach — an hour before food or two hours after. Food substantially reduces how much penicillin V is absorbed, and taking it with meals is a common reason a course underperforms.
Finish the entire course, even once the throat feels better. For strep throat this is what prevents rheumatic fever.
Shake the bottle, use the measure supplied, and check whether it needs refrigeration and how many days it keeps once made up.
Tell your prescriber or pharmacist if:
- You are allergic to penicillin or any beta-lactam antibiotic. This is the essential question, and reactions can be severe.
- You have kidney disease.
- You are pregnant or breastfeeding.
- You take the contraceptive pill — vomiting or diarrhoea during a course can reduce its reliability.
- You take methotrexate or warfarin.
- The medicine is for a child — the amount is calculated by weight.
A four-times-a-day schedule on an empty stomach is awkward, and that is the main reason courses go unfinished. Ask the pharmacist to help you plan the timing around meals before you leave.
Follow the dispensing label. This page does not set doses.
Possible cautions and when to ask a pharmacist or doctor
Allergic reactions. Penicillin allergy ranges from a mild rash to anaphylaxis. Seek emergency care for swelling of the face, lips or tongue, difficulty breathing, or a widespread rash with faintness.
Note that many people labelled penicillin-allergic in childhood are not in fact allergic — a rash during a viral illness is often mistaken for one. That label matters, because it pushes treatment toward broader and less suitable antibiotics for life. If you carry a penicillin allergy label you are unsure about, it is worth asking your doctor about proper assessment.
Diarrhoea is common and usually mild. Severe, watery or bloody diarrhoea, particularly with fever and particularly after the course ends, can indicate Clostridioides difficile infection.
Thrush may follow, though less often than with broader antibiotics.
If there is no improvement in two or three days, or things worsen, go back. A sore throat not responding to penicillin may be viral, or something else.
Do not share it or keep leftovers. There should be none if the course is finished.
Seek urgent medical attention for facial or throat swelling, difficulty breathing, a widespread rash — especially one that blisters or peels — severe or bloody diarrhoea, a high fever that is not settling, difficulty swallowing or drooling with a very sore throat, or an infection spreading despite treatment.
Related medicine guides
Frequently asked questions
What is Betapen used for? Streptococcal throat infections and tonsillitis, scarlet fever, ear, skin and dental infections, and long-term prevention of rheumatic fever. It contains penicillin V.
Why must it be taken on an empty stomach? Food substantially reduces absorption. Take it an hour before eating or two hours after.
Why do I have to finish the course if the throat is better? For strep throat, the full course is what prevents rheumatic fever, which can permanently damage heart valves. The throat improving is not the goal.
How is it different from amoxicillin? Penicillin V is narrow-spectrum and targeted at streptococci; amoxicillin covers a wider range. Narrower is better when the likely organism is known.
Can I take it if I am allergic to penicillin? No. Penicillin V is a penicillin. Tell your prescriber so an alternative such as a macrolide can be used.
Why is my child taking it every day for years? That is preventive treatment after rheumatic fever, or for someone without a working spleen. It prevents serious infection rather than treating anything present.