The dosage of penicillin for sinusitis varies depending on the type used and the patient's age, weight, and overall health.

Adults: 250-500 mg taken FOUR times a day for 7 days.

Try to space the doses evenly throughout the day. If you take phenoxymethylpenicillin 4 times a day, this could be first thing in the morning, around midday, late afternoon and at bedtime.

If you're taking it twice a day, leave 12 hours between each dose. For example you could take it at 8am and 8pm.

It's best not to take phenoxymethylpenicillin at mealtimes because food can stop it from working well. Take it 30 minutes before a meal or at least 2 hours after you have eaten.

Swallow phenoxymethylpenicillin tablets whole. Do not chew or break them.

If you forget to take a dose, take it as soon as you remember, unless it's nearly time for your next dose. In this case, just leave out the missed dose and take your next dose at the usual time.

Never take 2 doses at the same time. Never take an extra dose to make up for a forgotten one.

If you forget doses often, it may help to set an alarm to remind you. You could also ask your pharmacist for advice on other ways to help you remember to take your medicine.

Penicillin is generally effective in treating bacterial sinusitis, especially when caused by common pathogens such as:

• Streptococcus pneumoniae
• Haemophilus influenzae
• Moraxella catarrhalis

However, some bacteria may be resistant to penicillin, which is why sometimes a combination antibiotic like amoxicillin-clavulanate is used.

Taking an extra dose of phenoxymethylpenicillin is unlikely to harm you or your child.

Taking more than 1 extra dose could make you feel sick and cause vomiting and diarrhoea. Rest and take it easy until these side effects get better. Speak to your pharmacist or doctor if you're worried.

Always use this medication exactly as your clinician has told you. Check with our clinical team or your GP or pharmacist if you are not sure.

Medicines and their possible side effects can affect individual people in different ways. The following are some of the side effects that are known to be associated with this medicine. Just because a side effect is stated here, it does not mean that all people using this medicine will experience that or any side effect.

The most common adverse effects are:

• Gastrointestinal adverse effects, such as diarrhoea, nausea, and vomiting.
• Hypersensitivity.
• Skin reactions.
• Thrombocytopenia.

The most significant adverse effect of penicillins is hypersensitivity, which causes rashes and anaphylaxis and can be fatal.

• Allergic reactions occur in 1–10% of people treated with a penicillin; anaphylactic reactions occur in fewer than 0.05% of people.
• People with a history of atopic allergy (for example, asthma, eczema, and hay fever) are at a higher risk of anaphylactic reactions to penicillins.
• People with a history of anaphylaxis, urticaria, or rash immediately after penicillin administration are at risk of immediate hypersensitivity and should not take phenoxymethylpenicillin.
• People with a history of a minor rash (non-confluent, non-pruritic rash restricted to a small area of the body) or a rash that occurs more than 72 hours after penicillin administration are probably not allergic to penicillin. Phenoxymethylpenicillin should not be withheld unnecessarily for serious infections, but the possibility of an allergic reaction should be noted. Other beta-lactam antibiotics (including cephalosporins) can be used.
• People allergic to one penicillin will be allergic to all because the hypersensitivity is related to the basic penicillin structure.
• People with a history of immediate hypersensitivity to penicillins may also react to cephalosporins and other beta-lactam antibiotics and so should not receive these antibiotics. There is some evidence of partial cross-allergenicity of penicillins and cephalosporins.
• If a penicillin (or another beta-lactam) antibiotic is essential in a person with immediate hypersensitivity to penicillins, specialist advice should be sought on hypersensitivity testing or using a beta-lactam antibiotic with a different structure to the penicillin that caused the hypersensitivity.

Antibiotic-associated colitis has been reported and may range in severity from mild to life-threatening.

• Consider this diagnosis in people who present with diarrhoea during or after treatment with any antibiotic.
• The risk is increased with longer durations of antibiotic treatments, multiple antibiotics prescribed concurrently, or multiple courses of antibiotics.

Other possible adverse effects include:

• Uncommon — arthralgia and leucopenia.
• Rare or very rare — agranulocytosis, angioedema, haemolytic anaemia, hepatic disorders, nephritis tubulointerstitial, neutropenia, seizure, and severe cutaneous adverse reactions (SCARs).
• Frequency unknown — circulatory collapse, coagulation disorder, eosinophilia, soft faeces, stomatitis, glossitis, fever, increased risk of infection, neurotoxicity, oral disorders, and paraesthesia.

For full information on side effects and correct use, see the patient information leaflet. If any side effects concern you, or you are experiencing any of the side effects mentioned in the patient information leaflet whilst taking this medication, please contact our clinical team or speak to your GP.

Talk to your doctor, pharmacist or nurse before taking Phenoxymethylpenicillin Tablets: -

• 
  If you know that you are allergic to cephalosporins, any other antibiotic or any of the ingredients in your medicine
• If you suffer from kidney problems
• If you suffer from liver problems
• If you suffer any blood disorders
• If you are pregnant, trying for a baby or breast-feeding
• if you suffer from bronchial asthma or suffer from a tendency to develop allergic conditions such as hay fever or eczema.
• If you suffer from persistent diarrhoea or vomiting caused by stomach or intestinal problems or being sick, or are suffering from any gut disorder which may affect the way your body absorbs the medicine
• if you have suffered severe diarrhoea following previous treatment with antibiotics
• You are on a low-potassium diet. Each Phenoxymethylpenicillin 250 mg tablet contains 28 mg of potassium. This potassium content needs to be taken into consideration by patients with kidney problems or patients on a controlled potassium diet
• If you have a severe illness
• If you are on long-term treatment with Penicillin

Get emergency medical help if you have signs of an allergic reaction to this medication. These include:

• Hives
• Dizziness
• Fast or pounding heartbeats
• Wheezing
• Difficult breathing
• Swelling of your face, lips, tongue, or throat.

It is important that you let us know which prescription, over-the-counter medicines and recreational drugs you are currently taking. You must also tell us about any other medical conditions that you currently have (or had in the past). This will help us ensure the prescribed medication is safe and appropriate for you to take.

For full information on warnings, medication interactions and contraindications, refer to the Patient Information Leaflet. Please read all packaging and the Patient Information Leaflet before taking any new medicine and inform our clinical team or your GP of medicines you are taking or intend to take.