Phenoxymethylpenicillin in Pregnancy and Breastfeeding
What the safety data shows about penicillin V for sore throat in pregnancy and while breastfeeding, and who you should speak to.
Part of our Sore Throat condition guide. For general dosing, see phenoxymethylpenicillin for sore throat.
Speak to a clinician who knows your pregnancy. This guide explains what UK guidance says, but medicines in pregnancy and breastfeeding should always be prescribed by someone with your full history and maternity notes in front of them — usually your midwife, GP or a pharmacist. Please do not use this page to self-prescribe.
Key fact: Penicillins are among the best-studied antibiotics in pregnancy, with decades of data showing no increased risk of birth defects. Phenoxymethylpenicillin remains first choice where a bacterial sore throat genuinely needs treating in pregnancy.
Phenoxymethylpenicillin in pregnancy
Phenoxymethylpenicillin, also called penicillin V, is generally considered suitable in pregnancy. It is one of the antibiotics clinicians reach for most readily when a pregnant patient needs treating, precisely because the safety picture is so well established.
Penicillins have been in widespread clinical use since the 1940s. That length of exposure across enormous numbers of pregnancies means the data available is far better than for most medicines. Studies have not shown an increased risk of birth defects, miscarriage or other adverse pregnancy outcomes associated with penicillin use.
80+ yrs
of clinical use, including in pregnancy
First
choice antibiotic in pregnancy for bacterial sore throat
~70%
of sore throats are viral and need no antibiotic at all
That last figure matters as much as the safety data. The safest antibiotic is still the one you do not need to take. Most sore throats in pregnancy, as outside it, are viral and will settle with rest, fluids and paracetamol.
Does the trimester matter?
For phenoxymethylpenicillin, less than you might expect. Unlike some medicines that carry specific trimester restrictions, penicillin V is generally considered suitable throughout pregnancy.
That is a meaningful contrast with the pain relief side of treatment, where timing does matter considerably. Ibuprofen and other anti-inflammatories are generally avoided in pregnancy and particularly after 20 weeks, whereas paracetamol remains the option of choice throughout. So in practice, pregnancy changes your painkiller more than it changes your antibiotic.
Weighing treatment against leaving it alone
Many people's instinct in pregnancy is to avoid all medicines. That instinct is sound in general and wrong in specific cases, so it is worth unpacking.
| Situation | Consideration |
|---|---|
| Viral sore throat (most cases) | No antibiotic needed or useful. Rest, fluids and paracetamol are the correct treatment. |
| Genuine bacterial infection | Leaving it untreated has its own risks. Treatment is usually the safer choice. |
| High fever | Sustained high temperature is itself best avoided in pregnancy and should be controlled with paracetamol and assessed. |
| Feeling systemically unwell | Needs assessment rather than watchful waiting. |
| Not improving after 3 to 5 days | Warrants review regardless of pregnancy. |
The answer is not "take antibiotics to be safe" and it is not "avoid all medicines". It is assessment — so that the minority who need treatment receive it and the majority who do not are spared it. Our guide on sore throat vs strep throat explains the features that distinguish the two.
If you are allergic to penicillin
Where penicillin cannot be used in pregnancy, erythromycin is generally preferred over clarithromycin. There is a longer and more reassuring body of safety data for erythromycin in pregnancy.
Clarithromycin is not absolutely contraindicated and may still be appropriate in some circumstances, but it would not be the automatic first alternative in pregnancy the way it is outside it.
This is a decision for a clinician, not a menu to pick from. It depends on how genuine and how severe your penicillin allergy is, how unwell you are, how far along you are, and what else you take. It also matters that more than 90 per cent of people carrying a penicillin allergy label are not actually allergic on formal testing — which is worth investigating outside of pregnancy, not during an acute illness.
Breastfeeding
Phenoxymethylpenicillin is generally considered compatible with breastfeeding. Only very small amounts pass into breast milk, and the quantity a healthy full-term baby would receive is not expected to cause problems.
What to watch for in your baby
- Looser stools than usual
- Oral thrush — white patches in the mouth
- Nappy rash that looks like thrush
- Unusual irritability or feeding changes
These are uncommon and usually mild. Mention them to your health visitor, GP or pharmacist, who can advise and treat thrush if needed. They are not usually a reason to stop either the antibiotic or breastfeeding.
You do not need to interrupt breastfeeding or discard milk to take phenoxymethylpenicillin, unless a clinician who knows your situation has specifically told you otherwise. Advice to "pump and dump" is often applied far more broadly than the evidence supports.
Additional caution applies if your baby was premature, has a health condition, or is very young. Tell your prescriber these details.
Fertility and contraception
There is no evidence that phenoxymethylpenicillin affects fertility in men or women.
It also does not reduce the effectiveness of hormonal contraception. UK guidance on this changed some years ago: most antibiotics, penicillins included, are no longer considered to interact with the pill. The exceptions are enzyme-inducing antibiotics such as rifampicin and rifabutin, which are not used for sore throat.
The practical caveat is illness rather than the drug. If an infection makes you vomit or gives you significant diarrhoea, absorption of oral contraceptives can be affected. Follow the missed-pill advice in your contraceptive leaflet in that situation.
Pain relief for a sore throat in pregnancy
This is where pregnancy genuinely changes the advice, and it catches people out because they reach for what they would normally take.
| Option | In pregnancy | Notes |
|---|---|---|
| Paracetamol | Pain reliever of choice | Lowest effective dose, shortest time needed. |
| Ibuprofen and other NSAIDs | Generally avoided | Particularly after 20 weeks and in the third trimester. Check before use. |
| Benzydamine spray or rinse | Check first | Minimally absorbed but still an NSAID. Advice varies by product — ask a pharmacist. |
| Medicated lozenges | Check the pack | Suitability varies by active ingredient. |
| Salt water gargle | Suitable | Gargled and spat out. Simple and harmless. |
| Honey in warm water | Suitable | Soothing, no restriction in pregnancy. |
Do not assume a pharmacy product is automatically safe in pregnancy because it does not need a prescription. Throat sprays, lozenges and cold remedies vary widely, and some combination products contain ingredients best avoided. Always check the specific pack and ask a pharmacist.
Self-care that is safe in pregnancy
- Rest — genuinely the most useful thing, and the hardest to actually do
- Fluids — steady sipping through the day, warm or cool as you prefer
- Salt water gargles — half a teaspoon of salt in warm water, gargled and spat out
- Honey — on its own or in a warm drink
- Cool or soft foods — if swallowing hurts, ice lollies and yoghurt help
- Humidified air — particularly overnight if the room is dry
- Avoiding smoke — including second-hand
- Paracetamol at the correct dose — regularly rather than occasionally, if needed
Who to speak to
In pregnancy, the route to advice matters more than usual.
Your midwife
The first port of call for anything in pregnancy, including whether a symptom needs escalating.
Your GP
Can examine you, assess whether an antibiotic is warranted and prescribe with your full record available.
A pharmacist
Free advice without an appointment on which over-the-counter products are suitable in pregnancy.
NHS 111
Out of hours, or when you are unsure how urgently something needs looking at.
A note on our online service. Access Doctor's online sore throat consultation is available to adults aged 18 and over. If you are pregnant or breastfeeding, tell us at consultation. Our prescribers will review your circumstances and, where treatment in pregnancy needs direct clinical oversight or examination, we will advise you to see your GP or midwife instead of issuing a prescription. That is the right outcome, not a failed order.
When to get urgent help
Call 999 or go to A&E if there is difficulty breathing, a high-pitched noise when breathing, drooling or inability to swallow saliva, inability to open the mouth, or a rash that does not fade when pressed with a glass.
Contact your midwife, maternity unit, GP or NHS 111 the same day if you have a temperature of 38C or above that paracetamol is not controlling, you feel very unwell, you cannot keep fluids down, your symptoms are worsening after three to five days, or you have any concerns about your baby's movements.
Frequently Asked Questions
Is phenoxymethylpenicillin safe in pregnancy?
Phenoxymethylpenicillin is generally considered suitable during pregnancy and remains the first-choice antibiotic where a bacterial sore throat needs treating. Penicillins have been used in pregnancy for decades and there is a large body of safety data showing no increased risk of birth defects. That said, any medicine in pregnancy should be prescribed by a clinician who knows your full history, so speak to your midwife, GP or pharmacist rather than deciding for yourself.
Can I take penicillin V while breastfeeding?
Phenoxymethylpenicillin is generally considered compatible with breastfeeding. Only very small amounts pass into breast milk and it is not expected to cause problems for a healthy full-term baby. Occasionally a breastfed baby may develop looser stools, oral thrush or mild irritability. Mention any of these to your health visitor or GP, and tell your prescriber you are breastfeeding before starting any antibiotic.
Which antibiotic is used for sore throat in pregnancy if I am allergic to penicillin?
Erythromycin is generally preferred over clarithromycin during pregnancy, because there is a longer and more reassuring safety record for it. Clarithromycin is not absolutely ruled out and may still be chosen in some circumstances. This is a decision that needs a clinician who can weigh your allergy history, how unwell you are and how far along your pregnancy is, so it should not be self-selected.
Is it safer to leave a sore throat untreated in pregnancy?
Not necessarily, and this is a common misconception. Most sore throats in pregnancy are viral and genuinely do not need antibiotics, so leaving them alone is correct. But where there is a genuine bacterial infection, leaving it untreated carries its own risks, including a high fever that is itself best avoided in pregnancy. The right approach is assessment, so that the small number of people who need treatment get it and the majority who do not are spared it.
Can I take paracetamol or ibuprofen for a sore throat in pregnancy?
Paracetamol is the pain reliever of choice in pregnancy, taken at the lowest effective dose for the shortest time needed. Ibuprofen and other non-steroidal anti-inflammatories are generally avoided in pregnancy, particularly after 20 weeks and especially in the third trimester, because of effects on the baby's circulation and kidneys. Always check with a pharmacist, midwife or GP before taking any medicine in pregnancy, including products you would normally buy without advice.
Does phenoxymethylpenicillin affect fertility?
There is no evidence that phenoxymethylpenicillin affects fertility in either men or women. It also does not reduce the effectiveness of hormonal contraception. If an infection causes vomiting or significant diarrhoea, absorption of contraceptive pills can be affected, so follow the missed-pill advice in your contraceptive leaflet in that situation.
Can I use a Difflam throat spray while pregnant?
Benzydamine products are absorbed only minimally into the bloodstream because they act locally on the throat, but they are still non-steroidal anti-inflammatories and pregnancy advice varies between products and formulations. Do not assume a pharmacy product is automatically fine in pregnancy. Check the specific pack leaflet and speak to a pharmacist, midwife or GP before using it.
Getting advice and treatment
If you are pregnant or breastfeeding and have a sore throat, start with your midwife, GP or a pharmacist. They can assess whether treatment is needed and prescribe with your maternity record in front of them, which is the safest route.
Access Doctor's online sore throat service is available to adults aged 18 and over, and our GPhC-registered pharmacist independent prescribers review every consultation individually. Please tell us if you are pregnant, might be pregnant or are breastfeeding, so your prescriber can decide whether online treatment is appropriate or whether you should be seen in person. You can see the full range on the sore throat treatment page.
Antibiotic · Rx
Phenoxymethylpenicillin 250mg
First-line antibiotic for bacterial sore throat, including in pregnancy where treatment is needed.
View product →Antibiotic · Rx
Clarithromycin 500mg
Penicillin-allergy alternative outside pregnancy, where erythromycin is usually preferred.
View product →References
- NHS. Pregnancy, breastfeeding and fertility while taking phenoxymethylpenicillin. nhs.uk
- Joint Formulary Committee. British National Formulary: phenoxymethylpenicillin. bnf.nice.org.uk
- National Institute for Health and Care Excellence. Sore throat (acute): antimicrobial prescribing (NG84). nice.org.uk
- UK Teratology Information Service. Best Use of Medicines in Pregnancy (BUMPS). medicinesinpregnancy.org
- NHS. Paracetamol for adults. nhs.uk
- NHS. Ibuprofen for adults. nhs.uk
- Faculty of Sexual and Reproductive Healthcare. Drug interactions with hormonal contraception. fsrh.org
Medical disclaimer: This article is for informational purposes only and does not constitute medical advice. Always consult a qualified healthcare professional for diagnosis and treatment, and speak to your midwife, GP or pharmacist before taking any medicine in pregnancy or while breastfeeding. In a medical emergency, call 999.