Analgesics
Analgesics are drugs for relieving pain
I. Paracetamol (Acetaminophen)
II. Non-steroidal anti-inflammatory drugs (NSAID)
III. Opioid analagesics
IV. Non-opioid centrally acting analgesics
V. Compound/combined analgesic preparations
The non-opioid drugs, paracetamol and NSAIDs (and other NSAIDs), are particularly
suitable for pain in musculoskeletal conditions, whereas the opioid analgesics are
more suitable for moderate to severe pain, particularly of visceral origin and cancer
related pain.
I. Paracetamol (Acetaminophen)
It is a weak COX-1 and COX-2 inhibitor in peripheral tissues and possesses no
significant anti-inflammatory effects.
The most important drugs used for the treatment of mild to moderate pain when an
anti-inflammatory effect is not necessary
Pharmacokinetics
administered orally
Absorption is related to the rate of gastric emptying, and peak blood concentrations
are usually reached in 30-60 minutes.
slightly bound to plasma proteins and is
partially metabolized by hepatic microsomal enzymes and converted to
acetaminophen sulfate and glucuronide, which are pharmacologically inactive.
Less than 5% is excreted unchanged.
A minor but highly active metabolite (N-acetyl-p-benzoquinone) is important in large
doses because it is toxic to both liver and kidney.
The half-life of acetaminophen is 2-3 hours and is relatively unaffected by renal
function.
Adverse effects
At larger doses: dizziness, excitement, and disorientation are seen.
Cases of renal damage without hepatic damage have occurred, even after usual
doses of acetaminophen.
, Indication and Dosing
1. Mild to moderate pain and Pyrexia
Oral dose
▶ Adult: 0.5–1 g every 4–6 hours; maximum 4 g per day (usually tid)
Intravenous infusion
▶ Adult (body-weight up to 50 kg): 15 mg/kg every 4–6 hours, dose to be administered over
15 minutes; maximum 60 mg/kg per day
▶ Adult (body-weight 50 kg and above): 1 g every 4–6 hours, dose to be administered over
15 minutes; maximum 4 g per day
Rectal route
▶ Adult: 0.5–1 g every 4–6 hours; maximum 4 g per day
2. Mild to moderate pain and pyrexia in patients with risk factors for hepatotoxicity
INTRAVENOUS INFUSION
▶ Adult (body-weight up to 50 kg): 15 mg/kg every 4–6 hours, dose to be administered over 15
minutes; maximum 60 mg/kg per day
▶ Adult (body-weight 50 kg and above): 1 g every 4–6 hours, dose to be administered over 15
minutes; maximum 3 g per day
3. Pain and Pyrexia with discomfort in children
Oral dose
▶ Child 3–5 months: 60 mg every 4–6 hours; maximum 4 doses per day Child 6–23 months:
120 mg every 4–6 hours; maximum 4 doses per day
▶ Child 2–3 years: 180 mg every 4–6 hours; maximum 4 doses per day
▶ Child 4–5 years: 240 mg every 4–6 hours; maximum 4 doses per day
▶ Child 6–7 years: 240–250 mg every 4–6 hours; maximum 4 doses per day
▶ Child 8–9 years: 360–375 mg every 4–6 hours; maximum 4 doses per day
▶ Child 10–11 years: 480–500 mg every 4–6 hours; maximum 4 doses per day
▶ Child 12–15 years: 480–750 mg every 4–6 hours;maximum 4 doses per day
▶ Child 16–17 years: 0.5–1 g every 4–6 hours; maximum 4 doses per day
Analgesics are drugs for relieving pain
I. Paracetamol (Acetaminophen)
II. Non-steroidal anti-inflammatory drugs (NSAID)
III. Opioid analagesics
IV. Non-opioid centrally acting analgesics
V. Compound/combined analgesic preparations
The non-opioid drugs, paracetamol and NSAIDs (and other NSAIDs), are particularly
suitable for pain in musculoskeletal conditions, whereas the opioid analgesics are
more suitable for moderate to severe pain, particularly of visceral origin and cancer
related pain.
I. Paracetamol (Acetaminophen)
It is a weak COX-1 and COX-2 inhibitor in peripheral tissues and possesses no
significant anti-inflammatory effects.
The most important drugs used for the treatment of mild to moderate pain when an
anti-inflammatory effect is not necessary
Pharmacokinetics
administered orally
Absorption is related to the rate of gastric emptying, and peak blood concentrations
are usually reached in 30-60 minutes.
slightly bound to plasma proteins and is
partially metabolized by hepatic microsomal enzymes and converted to
acetaminophen sulfate and glucuronide, which are pharmacologically inactive.
Less than 5% is excreted unchanged.
A minor but highly active metabolite (N-acetyl-p-benzoquinone) is important in large
doses because it is toxic to both liver and kidney.
The half-life of acetaminophen is 2-3 hours and is relatively unaffected by renal
function.
Adverse effects
At larger doses: dizziness, excitement, and disorientation are seen.
Cases of renal damage without hepatic damage have occurred, even after usual
doses of acetaminophen.
, Indication and Dosing
1. Mild to moderate pain and Pyrexia
Oral dose
▶ Adult: 0.5–1 g every 4–6 hours; maximum 4 g per day (usually tid)
Intravenous infusion
▶ Adult (body-weight up to 50 kg): 15 mg/kg every 4–6 hours, dose to be administered over
15 minutes; maximum 60 mg/kg per day
▶ Adult (body-weight 50 kg and above): 1 g every 4–6 hours, dose to be administered over
15 minutes; maximum 4 g per day
Rectal route
▶ Adult: 0.5–1 g every 4–6 hours; maximum 4 g per day
2. Mild to moderate pain and pyrexia in patients with risk factors for hepatotoxicity
INTRAVENOUS INFUSION
▶ Adult (body-weight up to 50 kg): 15 mg/kg every 4–6 hours, dose to be administered over 15
minutes; maximum 60 mg/kg per day
▶ Adult (body-weight 50 kg and above): 1 g every 4–6 hours, dose to be administered over 15
minutes; maximum 3 g per day
3. Pain and Pyrexia with discomfort in children
Oral dose
▶ Child 3–5 months: 60 mg every 4–6 hours; maximum 4 doses per day Child 6–23 months:
120 mg every 4–6 hours; maximum 4 doses per day
▶ Child 2–3 years: 180 mg every 4–6 hours; maximum 4 doses per day
▶ Child 4–5 years: 240 mg every 4–6 hours; maximum 4 doses per day
▶ Child 6–7 years: 240–250 mg every 4–6 hours; maximum 4 doses per day
▶ Child 8–9 years: 360–375 mg every 4–6 hours; maximum 4 doses per day
▶ Child 10–11 years: 480–500 mg every 4–6 hours; maximum 4 doses per day
▶ Child 12–15 years: 480–750 mg every 4–6 hours;maximum 4 doses per day
▶ Child 16–17 years: 0.5–1 g every 4–6 hours; maximum 4 doses per day
