Antibiotic/Antiviral Therapy

Antibiotic/antiviral therapy is a course of medicine given to fight a bacterial or viral infection inside the body.

Bacteria and viruses are germs that can invade and damage the body's tissues. Antibiotics work by killing bacteria or stopping them from multiplying. Antivirals work differently — they block the steps a virus needs to copy itself, which reduces the amount of virus in the body and gives the immune system (the body's natural defence system) a chance to recover. Neither type of medicine works against the other's target: antibiotics do not kill viruses, and antivirals do not kill bacteria.

A doctor prescribes antibiotic or antiviral therapy when tests or clinical signs confirm that an infection is caused by a bacterium or a virus that is likely to respond to medicine. The choice between the two types — and which specific agent is used — depends on the germ identified, the organ affected, and how seriously ill the patient is.

• Bacterial infections such as pneumonia (a lung infection), urinary tract infections, skin and wound infections, tuberculosis (TB), and bloodstream infections (sepsis).
• Sexually transmitted infections caused by bacteria, such as chlamydia, gonorrhoea, and syphilis.
• Viral infections such as influenza (flu), HIV (the virus that can lead to AIDS), hepatitis B and hepatitis C (viral liver infections), herpes, and COVID-19.
• Infections that develop after surgery or in patients with weakened immune systems.
• Prevention of infection in high-risk situations, for example after close contact with someone who has a serious contagious disease.

There are situations where antibiotic or antiviral therapy is not appropriate. Doctors usually avoid prescribing antibiotics for illnesses caused by viruses, such as the common cold, because the medicine will not help and overuse can cause antibiotic resistance (when bacteria learn to survive despite the medicine). Similarly, not every viral infection requires antivirals — many mild viral illnesses resolve on their own with rest and supportive care.

• Common colds and most sore throats caused by viruses — antibiotics offer no benefit.
• Known allergy or severe previous reaction to the specific class of medicine being considered.
• Infections caused by germs that are already resistant to a particular antibiotic.
• Certain liver or kidney conditions that make it unsafe to process a specific medicine — your doctor will choose an alternative.

Antibiotic and antiviral therapy is generally well tolerated, but like all medicines, it can cause unwanted effects in some people.

• Digestive upset — nausea, vomiting, diarrhoea, or stomach cramps are the most common side effects of many antibiotics.
• Allergic reaction — ranging from a mild skin rash to, rarely, a severe whole-body reaction called anaphylaxis (a sudden, life-threatening allergic response).
• Yeast or fungal overgrowth — antibiotics can disturb the normal balance of harmless microbes in the gut or vagina, sometimes leading to a secondary infection such as oral thrush or a vaginal yeast infection.
• C. difficile colitis — a gut infection (inflammation of the large intestine) caused by a bacterium that can overgrow after broad-spectrum antibiotics are used.
• Liver or kidney strain — some medicines are processed by the hati (liver) or ginjal (kidneys) and may affect their function, especially with long courses.
• Antibiotic resistance — if a course is not completed as directed, surviving bacteria may become harder to treat in the future.
• Specific side effects linked to certain antivirals — for example, some medicines used for HIV or hepatitis can affect cholesterol levels or bone density over time; your doctor monitors for these.

Preparation for antibiotic or antiviral therapy is usually straightforward. Unlike surgery, there is normally no need to fast (go without food or drink) before starting oral tablets or capsules. However, some medicines work best taken on an empty stomach, while others are better absorbed with food — the prescribing doctor or pharmacist will explain this for the specific medicine chosen.

Before treatment begins, the care team will usually want to identify the exact germ causing the infection. Common tests include:

• Cultures — samples of blood, urine, sputum (mucus coughed up from the lungs), or wound fluid are sent to a laboratory to grow and identify the bacteria or virus present.
• Sensitivity testing — the laboratory checks which medicines the identified germ responds to, helping the doctor choose the most effective option.
• Blood tests — to check the function of the liver and kidneys before starting a medicine that is processed by those organs, and to measure the severity of infection (for example, through inflammatory markers).
• Rapid antigen or PCR tests — for certain viral infections such as influenza or COVID-19, a quick swab test can confirm the virus type within hours.
• Imaging — a chest X-ray or CT scan may be ordered if a lung or organ infection is suspected, to understand how severe it is.

During the procedure itself, the steps depend on how the medicine is given:

• 1. The doctor reviews test results and selects the most appropriate medicine and the correct length of course.
• 2. For mild to moderate infections, the medicine is usually prescribed as tablets or capsules taken at home.
• 3. For serious or hospital-acquired infections, the medicine may be given through an intravenous (IV) drip — a thin tube placed into a vein, usually in the arm — so that it enters the bloodstream directly and works faster.
• 4. Nursing staff monitor the IV site for any signs of irritation or leakage during intravenous treatment.
• 5. The doctor adjusts the type or duration of treatment if test results, allergy information, or the patient's response require a change.

Patients who smoke or drink alcohol are usually advised to reduce or stop during the course, as both can interfere with how the body processes certain medicines and can slow recovery from infection. Patients already taking blood thinners, immunosuppressants (medicines that reduce immune activity), or other regular medicines should tell their doctor, because interactions are possible.

Recovery after antibiotic or antiviral therapy depends on the type and severity of the infection being treated. Patients with mild infections who take oral medicine at home usually continue their normal daily activities, though rest is encouraged while symptoms are present. Patients who received intravenous treatment in hospital are usually monitored until their temperature, blood pressure, and key blood markers return to a safe range before they are discharged.

• Complete the full course of medicine even if you feel better early — stopping too soon can allow the infection to return and may contribute to resistance.
• Attend follow-up blood tests or imaging appointments if your doctor schedules them, to confirm the infection has cleared and to check that the liver and kidneys were not affected.
• Report new or worsening symptoms promptly — fever returning, a new rash, severe diarrhoea, or yellowing of the skin or eyes — as these may signal a complication or an allergic reaction.
• Manage digestive side effects by eating yoghurt with live cultures or taking probiotic supplements (products that restore healthy gut bacteria) if your doctor agrees this is appropriate for your situation.
• Avoid alcohol during and for a short time after certain antibiotic and antiviral courses, as it can reduce the medicine's effectiveness or worsen side effects.
• For long-term antiviral therapy — such as for HIV or chronic hepatitis — regular monitoring appointments (usually every few months) check that the virus remains suppressed and that organ function stays normal.
• Discuss vaccination options with your doctor after recovery, as some preventable infections (such as influenza or pneumococcal pneumonia) can be avoided with vaccines.