Medicines

How to calculate paracetamol dose for infants & children by body weight?

calculate paracetamol dose Posted On
Posted By SUMIT SHARMA

Introduction 

Whenever your child gets a fever, you usually give paracetamol. Do you know the correct dosage of paracetamol and how to calculate paracetamol dose for kids? 

Paracetamol is absolutely 100% safest medicine if you take it at the right time and correct dose. 

Since paracetamol is an OTC (Over the counter) medicine or non-prescription drug, you can easily find it in most homes.

Paracetamol comes in the market in various dosage forms (such as syrup, drops, tablets), strength (such as 120mg/5ml, 125mg/5ml, 250mg/5ml), and brand names (such as Paracip, Pyrigesic, Calpol, Dolo, Sumo L, etc.). 

Sometimes, you usually get confused – 

How much?

How often?

& Which one should I give paracetamol to our children?

You’re not the only one experiencing this problem. A lot of people do not know the correct dosage of paracetamol.

Suppose you unintentionally give paracetamol overdose to your kids. It may cause acute liver failure and is more prone in less than 5 years old children. Sometimes, it could be fatal in infants

So, the dosing error of paracetamol is the most significant concern in public health. 

However, I’ll do my best to answer this million-dollar question in this post. I’ll describe how to calculate paracetamol dose in infants, children, and adults.

Before that, let’s grab some basic information about paracetamol – 

 

What type of drug is paracetamol?

Paracetamol is one of the most popular medicines in the world. It is the first-line choice over-the-counter medicine for children to treat fever and mild pain.

Paracetamol is derived from the para-aminophenol group. This means the paracetamol structure contains a hydroxyl group (OH), amide group (HN-CO-R), and an aromatic group (benzene ring). It is often known as “acetaminophen.” 

Paracetamol or acetaminophen has two important properties – antipyretic (to reduce fever) and mild analgesic (pain reliever). 

This drug doesn’t have anti-inflammatory activity because it has a negligible effect on the COX enzyme (cyclooxygenase) in the peripheral. So, paracetamol is not considered an NSAID (Non-steroidal Anti-inflammatory drug).

Due to the lack of anti-inflammatory activity, acetaminophen is only used to reduce the high body temperature and body pain (such as headache, muscle pain, back pain, and toothache).

In addition to children, paracetamol is prescribed to adults and those over the age of 65. It is one of the first-line medications for treating osteoarthritis.

In general, acetaminophen is a well-tolerated medication with minimal side effects.

 

What does paracetamol do to the body?

When you take paracetamol, it enters your stomach. Here, paracetamol gets disintegrates and dissolves. After that, it is rapidly absorbed from the small intestine of the duodenum and enters your blood circulation. 

Calculate paracetamol dose

Paracetamol is almost well distributed to the entire tissues of your body.

The primary mechanism of action of paracetamol in your brain. Paracetamol rapidly crosses your blood-brain barrier because it is a highly lipid-soluble drug. 

When paracetamol enters your brain, it stops prostaglandin production by inhibiting COX-2 (Cyclo-oxygenase). 

After providing the therapeutic action of paracetamol, this medicine goes to your liver for metabolism. 

Your liver starts the glucuronidation reaction of paracetamol. In this glucuronidation, paracetamol gets conjugate with glucuronic acid and sulfuric acid. 

This glucuronidation process makes the paracetamol inactive; as a result, it forms inactive metabolites – paracetamol glucuronidated or sulphated. 

The glucuronidation and sulfation process also converts the lipophilic (lipid solubility) paracetamol into hydrophilic (water solubility) paracetamol. 

This process enhances the excretion of the inactive metabolite of paracetamol (water-soluble) through urine.

Moreover, acetaminophen also forms a minor toxic metabolite – NAPQI (N-acetyl benzoiminoquinone) in your liver. This NAPQI is a highly reactive and potentially dangerous metabolite of paracetamol. 

NAPQI is mainly responsible for liver damage

Fortunately, acetaminophen medication is metabolized by glucuronidation. Glucuronidation is an important process of metabolism because it helps in detoxifying the NAPQI metabolite.  

 

How to calculate paracetamol dosage for infants?

According to a study, paracetamol is the only medicine to treat fever and pain if your baby is less than 3 months old. 

In this case, you should give paracetamol 10 mg/kg dose every 4-6 hours intervals. 

Paracetamol dose for newborn (one month baby)

You should strictly avoid paracetamol in a newborn baby or weight less than 2 kg unless prescribed by a doctor. Because there is a high chance of liver toxicity in neonates. 

The glucuronidation pathway is not fully developed in small children (under two years of age). As children grow, the glucuronidation process starts to develop, and this could take two years to fully mature. 

Neo-born children have a deficiency in a conjugating systems like glucuronic acid and sulfuric acid. Due to this, NAPQI makes a covalent bond with hepatocytes (liver cells) that damages your child’s liver. 

Therefore, paracetamol is not recommended in newborn children. 

Paracetamol dose for 1 year baby

If your child is less than 1 year old, you can give paracetamol drops dosage for infants. 

Paracetamol drops come in various popular brand names such as SUMO L drops suspension, Calpol pediatric oral suspension, Dolo drops suspension, Paracip drops, etc. 

Calculate paracetamol dose

Generally, each ml drop suspension contains 100 mg paracetamol. 

If you want to calculate the proper dose of paracetamol, you should be aware of your child’s weight. Then, you just multiply the child’s weight by the recommended dose of paracetamol (15 mg/kg).

After that, divide it by the available strength of paracetamol. 

For example, your child’s weight is 5.5 kg. In this case, you will require (5.5 x 15) 82.5 mg paracetamol. 

If your paracetamol drops strength is 100 mg/ml. Then, you have to put it into the below formula – 

Paracetamol drops dosage calculation = Required dose / strength of drops

=82.5/100= 0.8 ml 

Paracetamol dosing chart for infants – 

Calculate paracetamol dose

 

How to calculate paracetamol dose for children, and how much paracetamol should I give?

Globally, it is generally recommended to take a paracetamol dose between 10 to 15 mg/kg

Here, we will calculate a safe paracetamol dose for your child by simple body weight.

Required paracetamol dose in milligrams (mg)

The dose of paracetamol is generally based on your body weight. You can calculate your paracetamol dose for the child per kg formula. 

Suppose your child’s body’s weight is 20 kg. You need to just multiply the child’s body weight by the recommended dose of paracetamol. 

Paracetamol dose for 20 kg weight = Body weight x Recommended paracetamol dose

= 20 x 15 =300 mg 

You will require 300 mg paracetamol for 20 kg body weight. 

Dosage should be repeated every 4-6 hours if necessary (max 4 dosages in 24 hours). You should not give your child more than four doses of paracetamol within 24 hours.

 

Required paracetamol dose in milliliters (ml)

Paracetamol syrup comes in three strength 120 mg/5 ml, 125 mg/5 ml, and 250 mg/ 5 ml. We can calculate pediatric paracetamol dose in milliliters (ml) for different body weights.

Calculate paracetamol dose

Calculate paracetamol dose

Examples of calculating a paracetamol dose –

  • Paracetamol dose for toddler/preschool (aged 2-3 years) 

Suppose you have paracetamol syrup 120 mg/5 ml of strength. This means each 5 ml of syrup contains 120 mg of paracetamol. 

Calculate paracetamol dose

Firstly, you have to calculate the required dose of paracetamol for toddlers. Generally, the expected body weight of a 2-3 years child is 13 kg. 

The required dose of paracetamol would be (13 x 15) 195 mg. 

Paracetamol 120 mg dosage calculation = required dose in mg/syrup strength available (120 mg/5 ml)

=195 x 5/120

=8.1 ml

You will have to give 8 ml paracetamol syrup 120 mg/5 ml for 13 kg child weight every 4-6 hours interval. 

But suppose you have paracetamol syrup 125 mg/5 ml or 250 mg/5 ml. 

Paracetamol 125 mg dosage calculation = required dose in mg/syrup strength available (125 mg/5 ml)

=195 x 5/125

=7.8 ml

Paracetamol 250 mg dosage calculation = required dose in mg/syrup strength available (250 mg/5 ml)

=195 x 5/250

=3.9 ml

Paracetamol suppository for 2 to 5 years old – 

If your baby is unable to take paracetamol from the mouth. You may give paracetamol suppository to your baby through the rectal route under the proper medical supervision. 

Paracetamol suppository is well absorbed by the rectal route. 

Paracetamol comes in the brand name Rectol, Neomol anal suppository 80, 125, 250 mg

  • Paracetamol dose for 5 years old child

The expected child weight for 5 years is 18 kg. The required dose of paracetamol will be (18 x 15) 270 mg for 18 kg body weight. 

Paracetamol 120 mg syrup dosage calculation = 270 x 5/120=11.2 ml

Paracetamol 125 mg syrup dosage calculation = 270 x 5/125=10.8 ml

Paracetamol 250 mg syrup dosage calculation = 270 x 5/250=5.4 ml

  • Paracetamol dose for 10-years old

If your child’s age is 10 years old, it is generally expected to be 32 kg. The required dose of paracetamol will be (15 x 32) 480 mg for 32 kg body weight. 

It is not required to give syrup or suspension in this age group. You can give paracetamol 500 mg tablet for 10 years child every 4-6 hours. 

  • Paracetamol dosage for 12-15 years old

It is generally expected to be 42-50 kg weight for a 12 to 15 years old. 

For example, if your child’s weight is 46 kg. Then you will have to give 690 mg of acetaminophen to your child. 

In this age group, you can give paracetamol 650 mg (DOLO or Calpol) tablet for 46 kg body weight every 4-6 hours intervals.

 

Paracetamol dosing chart for children –

Calculate paracetamol dose

  

How to calculate paracetamol dose for adults or older adults?

For adults, the usual dosage for paracetamol is between 0.5 and 1 g

If you are an adult or older, you can take a standard dose of paracetamol 500 mg or 650 mg, as per your need or clinical situation. 

Paracetamol 650 mg works better as pain relief. 

You can take paracetamol every 4-6 hours if necessary; however, never take this medicine in more than four doses in one day. 

Paracetamol tablet comes in popular brand names like DOLO 650, Calpol 500/650, Paracip 500, Crocin advance etc.

Calculate paracetamol dose

 

What is the maximum dosage of paracetamol per day?

The maximum dose of paracetamol is 4 g (or 4000 mg) per day. You should never take paracetamol more than 4 g within a day. 

Paracetamol is itself a toxic drug because it contains a poisonous metabolite – NAPQI, which is dangerous for our liver.

Fortunately, the liver helps to detoxify the NAPQI metabolite through the glucuronidation process. 

Paracetamol is not recommended for infants weighing less than 2 kg due to the risk of hepatotoxicity.

There is no formula to calculate paracetamol toxicity. Suppose you take a heavy dose of paracetamol (> 150 mg/kg or > 10 g in an adult). In that case, there is a high chance of serious liver toxicity.

Paracetamol may be lethal; if you are taking an acetaminophen dose of more than 250 mg/kg or 10–15 g (20–30 tablets) can lead to fatal liver toxicity. 

Thus, you should never take more paracetamol than the recommended dose.

 

What are the side effects of paracetamol?

The primary cause of paracetamol’s side effects is dosing error. An incorrect dosage of paracetamol may cause acute liver failure in children. 

It will be shocking to know that paracetamol toxicity is the second leading cause of liver transplantation globally. 

There are three most common dosing errors include – 

  • If you have taken an excessive recommended dose of paracetamol
  • If you are taking paracetamol dose too frequently (more than 4 times a day)
  • If you are taking paracetamol for an extended period

 

In another research study, it was found that the inappropriate dose of paracetamol may cause long-term neurodevelopment problems in infants and children. 

 

How long does paracetamol take to work?

The maximum paracetamol concentration reaches your blood within 20 minutes when you are on an empty stomach. 

If you take paracetamol after a meal, it takes 60 minutes to reach maximum blood concentration. 

Overall, the onset of action of paracetamol is 30 min.

Paracetamol drug remains in your blood for up to 3 to 4 hours because the half-life of paracetamol is 2 hours. 

 

Conclusion

Paracetamol is an absolutely safe, effective, and well-tolerated medicine when you take it in the appropriate and recommended dose. 

There are some crucial points you need to consider while calculate paracetamol dose for your child – 

  • You should always give paracetamol to your children as per their body weight. NOT age. 
  • Overdosing of paracetamol may cause liver toxicity, especially in less than 5 years old. 
  • Paracetamol provides your child only symptomatic relief in controlling fever or body pain. Still, it does not cure the cause of the disease. 
  • If your child is not getting relief after administering the paracetamol drug, you must consult an expert doctor. 

 

If you find this post (calculate paracetamol dose) informative, please share it on social media. 

 

FAQ

Q 1. Which paracetamol brand is best for fever?

The effectiveness of paracetamol does not depend on the brand name of the medicine. You can take any brand of paracetamol, such as DOLO, Calpol, Paracip, SumoL, etc., in recommended dosing strength.  

 

Q 2. What is the appropriate dose of paracetamol for pain management in children?

Always follow the bodyweight formula (10-15mg/kg) if you give paracetamol medicine to your child for pain management or fever. But if you are an adult, Paracetamol 650 mg is generally recommended for muscle pain, dental pain, period pain, back pain, and sore throat. 

 

Q 3. Is paracetamol safe for pregnancy?

Paracetamol is the only safest painkiller in pregnancy and breastfeeding conditions. According to a recent study in 2022, paracetamol does not cause an increased risk of perinatal outcomes; however, paracetamol should not be considered a risk-free medication. So, you should take paracetamol under proper medical supervision. 

 

Q 4. What would be the paracetamol dose in pregnancy?

Since paracetamol is the first-choice painkiller for a pregnant female. As per a study, you can take 500 to 650 mg of acetaminophen every 4-6 hours, depending on your need; but it should never exceed the recommended maximum daily intake dose of 4000 mg. 

 

Q 5. What would be the paracetamol dose in dengue fever?

Paracetamol is a recommended medication for dengue fever. If your child has dengue fever, you can give paracetamol syrup as per their body weight every 6 hours (maximum 4 doses per day). You can take paracetamol tablet 500-650 mg every 6 hours for adults but not exceed the maximum daily dose of 4000 mg. 

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