DENT 3005: Introduction to Pharmacology¹

Drugs for pain relief

Dr Thuy Linh Truong thuy.truong@uwa.edu.au

Acknowledgement of country²

The University of Western Australia acknowledges that its campus is situated on Noongar land, and that Noongar people remain the spiritual and cultural custodians of their land, and continue to practise their values, languages, beliefs and knowledge.

THE UNIVERSITY OF WESTERN AUSTRALIA

Artist: Dr Richard Barry Walley OAM

Learning Outcomes³

Learning objectives

Understand the different types of analgesics and their mechanism of action
Understand the different types of local anaesthetics and their mechanism of action
Understand indication, dosing direction and regimen for analgesics in the dental setting
Understand indication, dosing direction and common techniques for local anaesthetics in the dental setting
Recognise oral and dental side effects of these drugs
Understand drugs interactions with dental medications
Applied knowledge to clinical scenarios

Cartoon showing a tooth receiving a local anesthetic injection, with three teeth appearing to be sleeping or sedated.

Pain⁴

Type

Nociceptive
Neuropathic
Mixed

Severity

Subjective
Assess behavior if patient unable to report pain

Pain Scales

Numerical
Visual
Verbal

Duration

Acute
Chronic

Verbal Pain Intensity Scale	Visual Analogue Scale
No Pain - Mild Pain - Moderate Pain - Severe Pain - Very Severe Pain - Worst Possible Pain	No Pain - Worst Possible Pain
0-10 Numeric Pain Intensity Scale	Wong-Baker FACES® Pain Rating Scale
0 - 1 - 2 - 3 - 4 - 5 - 6 - 7 - 8 - 9 - 10	0 No Hurt - 2 Hurts Little Bit - 4 Hurts Little More - 6 Hurts Even More - 8 Hurts Whole Lot - 10 Hurts Worst
No Pain - Moderate Pain - Worst Possible Pain

Acute Vs chronic⁵

Acute	Chronic
- Defined pattern of onset, site, character, duration	- >3months
- Cause: identifiable	- Persist even after healing
- Rational for drug use	- Rational for drug use
- Relieve suffering	- Relieve symptoms
- Reduce/prevent harmful physiological & psychological effects	- Maintain/restore function
- Reduce transition to chronic pain	- Improve quality of life
- Assist rehabilitation
- Practice point	- Practice point
- Treat the disease!	- Agree on realistic goals
- Patients on chronic opioid treatments	- Not (usually) possible to eliminate pain completely
	- Titrate and review regularly

Pain Management Principles⁶

Start early

May minimize $\to$ chronic pain

Route of administration

Oral
Parenteral
Other: transdermal, inhalation, epidural …

Additional considerations

Non-drug treatments
- CBT
- Heat/cold
- Massage etc…

The WHO analgesic ladder⁷

Step by step
Patients receive medication in increasing doses based on pain severity
Titrate dose against
Three steps
- Non-opioid analgesics
- Weak opioids
- Strong opioids

Additional considerations

Adjuvants
Maintained effective dose
Starting at the bottom is not always necessary
Pros and cons of each tx

graph TD subgraph Pain Ladder 4[Interventional treatments +/- nonopioid +/- adjuvant therapy **SEVERE to VERY SEVERE PAIN**] 3['Strong' opioid +/- nonopioid +/- adjuvant therapy **MODERATE to SEVERE PAIN**] 2['Weak' opioid or multimodal +/- nonopioid +/- adjuvant therapy **MILD to MODERATE PAIN**] 1[Nonopioid + adjuvant therapy **MILD PAIN**] end

Pain_Persistence[Pain persists or worsens]
Pain_Persistence --> 1
1 --> 2
2 --> 3
3 --> 4

subgraph Breakthrough Pain
    Acute[Acute]
    Intermediate[Intermediate]
    Chronic[Chronic]
end

subgraph Duration of Action
    Short_acting[Short-acting]
    Intermediate_acting[Intermediate-acting]
    Long_acting[Long-acting]
end

direction LR
Acute --> Intermediate
Intermediate --> Chronic

style Acute fill:lightblue
style Intermediate fill:lightblue
style Chronic fill:lightblue

Rapid_acting[Rapid-acting]
Rapid_acting --> Breakthrough[Breakthrough]

Breakthrough --> Acute
Breakthrough --> Intermediate
Breakthrough --> Chronic

Short_acting --> Acute 
Intermediate_acting --> Intermediate
Long_acting --> Chronic

Figure 3. An updated version of the 1986 WHO pain ladder. Persistent and chronic pain syndromes should be treated with long-acting opioids; rapid-onset opioids are appropriate for breakthrough pain. A fourth step has been added for “very severe” pain that can be treated with peripheral nerve blockade.

Pain types and analgesia⁸

Drugs	Nociceptive pain	Neuropathic pain
Paracetamol	Effective, regular and maximum dosing, nil anti-inflammatory effect	Less effective
Opioids	Effective	May be effective
NSAIDS	Effective (inflammatory pain)	Less effective
Antidepressants, antiepileptics, LAs	Rarely used	May be effective (TCAs & antiepileptics tx of choice)

Pain may be mixed

Orofacial pain⁹

Many causes
- Only some are dental
- Refer for non-dental origin
Patient assessment crucial
- Diagnosis
- Treatment planning
Acute dental pain
- Pulpitis, post-exo pain
Chronic dental pain
- TMD, BMS $\to$ refer
Analgesics: adjunct only
- Does not replace TREATMENT

Non-opioid analgesics¹⁰

Paracetamol

MOA: Not fully determined
- Maybe: inhibition of central prostaglandin synthesis
- Negligible anti-inflammatory effect
Drug interactions
- Very few clinically significant drug interactions
- Potentiation of hepatotoxicity in overdosage
ADR [common]
- Hepatotoxicity (overdose)
- Hypersensitivity reactions (rare)

Generic name	Brand Name
Paracetamol	Panadol

Route	Absorption	Time to peak	Time to effect
Oral	Rapid	10-60 minutes	15-30 minutes
IV	Rapid	15 minutes	5-10 minutes
Rectal	Slow, erratic	Slow, erratic	Slow, erratic

Dosage

Adult, child >12yo
- 0.5-1g every 4-6 hours, max 4g per 24hours
- CR 665mg: 2 tabs every 6-8 hours, max 6 tabs per day
Child >1month
- 15mg/kg every 4-6 hours

NSAIDs (Non-Steroidal Anti-Inflammatory Drugs)¹¹

Nonselective NSAIDs (COX1&2-Inh)		Selective NSAIDs (COX2-Inh)
Generic name	Brand Name	Generic name	Brand Name
Aspirin	Solprin	Celecoxib	Celebrex
Diclofenac	Voltaren	Etoricoxib	Arcoxia
Ibuprofen	Nurofen	Meloxicam	Melobic, Mobic
Indomethacin	Arthrexin	Parecoxib	Dynastat inj
Ketorolac	Indocid
Mefenamic Acid	Toradol
Naproxen	Inza, Naprosyn
Piroxicam	Feldene-D, Mobilis

Opioid analgesics¹²

MOA: mimic endogenous opioids, activate opioid receptors
Drug interactions
- CNS depressants
- Drugs lowering BP
- Drugs causing bradycardia
- SSRIs: Serotonin toxicity
ADR [common]
- Drowsiness, dizziness, headache, orthostatic hypotension, itch, dry mouth, constipation
- Dose related respiratory depression

Opioid Analgesics List

Buprenorphine
Codeine
Aspirin with codeine
Ibuprofen with codeine
Paracetamol with codeine
Fentanyl
Hydromorphone
Methadone
Morphine
Oxycodone
Oxycodone with naloxone
Pethidine
Tapentadol
Tramadol
Tramadol with paracetamol

Opioids in a Nutshell¹³

Drugs	Indications	Practice points
Oxycodone IR (S8) 5mg every 4-6 hours prn, max 3 days	Preferred in mod-severe acute dental pain	Always IR formulations as CR delayed onset not ideal S8 prescription rules
Tramadol (S4) 50-100mg every 4-6 hours prn, max 400mg per 24hours	Mild-mod pain • Useful if either NSAID’s or opioids are inappropriate or contraindicated • Useful if excessive respiratory depression, constipation, sedation or hypoxemia with other opioids • Useful to try to reduce overall opioid consumption	• Beware – LOTS of potential drug interactions • “Serotonin syndrome” • Caution if patient is on antidepressants • Caution if patient has epilepsy • Caution if patient on ketamine
Tapentadol (S8) 50mg bd, max 500mg per 24hours	Mod-severe pain Alternative if patient can’t tolerate opioids	Contraindication: patients starting on irreversible non-selective MOAIs Again IR>CR S8 prescription rules
Codeine (combination with paracetamol/ibuprofen) (S8) 30-60mg every 4 hours prn, max 240mg per 24hours	Mild-mod pain Cough suppressant	Commonly combination w/ paracetamol Combinations w/ ibuprofen: subtherapeutic dose <30mg Genetic polymorphisms: lack of CYP2D6 Not for <12!!!
Buprenorphine, dextropropoxyphene, fentanyl, hydromorphone, methadone, morphine, pethidine	• Very strong opioids • Patches or CR: mainly for chronic pain not acute dental pain • Opioid depended program • Adjunct in GA procedures

Therapeutic guide: analgesic regimen¹⁴

Mild – moderate
- Ibuprofen 400mg every 6-8 hours ( $\leq$ 5days) + paracetamol 1000mg q4-6h (4g/24hrs)
- Celecoxib 100mg bd ( $\leq$ 5days)
- Unless NSAIDs contraindicated
Severe acute
- Ibuprofen 400mg every 6-8 hours ( $\leq$ 5days) OR celecoxib
- - paracetamol 1000mg every 4-6 hours (4g/24hrs)
- - Oxycodone 5mg every 4-6 hours prn ( $\leq$ 3days)
- Unless NSAIDs contraindicated

VERSION 3

Local Anesthetics¹⁵

Introduction

A drug that causes reversible loss of sensation
Used to numb specific areas of the body
Allows pain-free dental procedures
Blocks nerve conduction temporarily
Does not affect consciousness
Used both topically and via injection

History

Cocaine was the first local anaesthetic
Introduced in dental use in the late 1800s
Safer synthetic alternatives developed later
Procaine (Novocain) was an early alternative
Lidocaine introduced in the 1940s

General Vs Local Anesthesia¹⁶

General	Local
• Effect: Affects your entire body	• Effect: Numbs a small, specific area of your body
• Consciousness: You are completely unconscious (asleep) and unaware of what’s happening	• Consciousness: You stay awake and alert
• Use: For major surgeries (e.g., heart surgery, brain surgery, or operations on internal organs)	• Use: Minor procedures (e.g., dental work, stitches, mole removal)
• How it’s given: Through a mask (gas) or an IV injection	• How it’s given: Usually injected directly into the area being treated
• Risks/Side Effects: Drowsiness, nausea, confusion after waking up; requires careful monitoring of heart, breathing, etc.	• Risks/Side Effects: Very few; may feel tingling or numbness for a while afterward

Local Anesthetics: MOA and Types¹⁷

MOA	Types
Blocks sodium channels in nerve membranes	• Amides: Lidocaine, Articaine, Mepivacaine
• Prevents initiation of nerve impulses	• Esters: Procaine, Benzocaine
• Stops pain signals from reaching the brain	• Amides metabolized in liver
• Works only on peripheral nerves	• Esters metabolized in plasma
• Action is reversible and dose-dependent	• Articaine has both amide & ester properties
• Onset and duration vary by agent

Local Anesthetics: Indications and Techniques¹⁸

Indications	Common techniques
• Tooth extractions	• Infiltration anaesthesia
• Root canal treatments	• Nerve block anaesthesia
• Restorative procedures (fillings)	• Intra-ligamentary injections
• Periodontal therapy	• Intra-pulpal injections
• Minor oral surgeries	• Topical anaesthesia before injection
	• Computer-controlled delivery systems

Local complications of local anaesthesia¹⁹

Neurological: paraesthesia, dysaesthesia, temporary facial nerve paralysis
Prolonged anaesthesia usually resolves; permanent anaesthesia is rare
Nerve injuries from trauma, bleeding, or neurotoxicity
Increased risk with repeat injections or high concentrations
Tissue trauma: haematoma, accidental intramuscular injection $\to$ trismus
Rare equipment-related issues (e.g., cartridge explosions)

Systemic toxicity of local anaesthetics²⁰

Causes: intravascular injection, overdose, rapid absorption
Prevention: use lowest effective dose, aspirate before injection
Early signs: anxiety, dizziness, tremors
Severe signs: seizures, cardiovascular collapse, methemoglobinemia
Actions: stop injection, support ABCs, consider lipid therapy

Local Anesthetics & vasoconstrictors²¹

Local anaesthetics can be combined with a vasoconstrictor to prolong effects
Vasoconstrictors slow anaesthetic absorption and reduce bleeding
Adrenaline (epinephrine) is commonly used in dental practice
Avoid adrenaline in patients sensitive to sulfites
Alternatives: Felypressin or adrenaline-free solutions
Felypressin is safe for pregnant patients and has minimal cardiac effects

Local Anesthetic Preparations²²

Local Anaesthetic	Comments
Short- to Intermediate-Acting Preparations
Lidocaine	Shorter acting—use in dentistry may be limited
Lidocaine with Adrenaline (Epinephrine)	Intermediate acting, first line for routine dental procedures
Prilocaine	Shorter acting—use in dentistry may be limited
Prilocaine with Adrenaline (Epinephrine)	Intermediate acting
Prilocaine with Felypressin	Intermediate acting, first line for routine dental procedures when adrenaline (epinephrine) is contraindicated
Mepivacaine	Shorter acting—use in dentistry may be limited, do not use in children younger than 3 years
Mepivacaine with Adrenaline (Epinephrine)	Intermediate acting, do not use in children younger than 3 years
Articaine with Adrenaline (Epinephrine)	Risk of prolonged or permanent anaesthesia, for infiltration only—do not use for regional blocks (injection close to inferior alveolar, lingual and mental nerves), do not use in children younger than 4 years
Long-Acting Preparations
Ropivacaine	Useful for situations in which prolonged analgesia (eg 12 to 18 hours) is required, postoperative pain, and refractory acute dental pain, concentrations up to 0.5% can be used in children
Bupivacaine	Similar indications to ropivacaine, more cardiotoxic than ropivacaine, cardiac toxicity may manifest before neurological toxicity, do not use in children younger than 12 years
Bupivacaine with Adrenaline (Epinephrine)	Similar indications to ropivacaine, more cardiotoxic than ropivacaine, cardiac toxicity may manifest before neurological toxicity, do not use in children younger than 12 years

Dosages in dentistry²³

Use the lowest effective dose of local anaesthetic to prevent dental pain
Maximum safe doses are listed for different local anaesthetics in dental cartridges and other forms
The required dose is often much lower than the maximum safe dose if administered correctly
The appropriate dose depends on the area, tissue vascularity, method, and patient condition
Children, especially young ones, are more susceptible to overdose and may require lower doses
Elderly patients may need reduced doses due to age-related physiological changes

Calculating Maximum Safe Volume²⁴

Here’s a simple way to calculate the maximum safe volume of local anaesthetic for a patient:

Find the maximum dose per kg for the drug (for lidocaine with adrenaline, it’s 7 mg/kg).
Multiply this by the patient’s weight in kg to get the total max dose in mg.
Convert this dose to volume using the drug concentration (lidocaine 2% = 20 mg/mL).
Convert volume to dental cartridges (each cartridge is 2.2 mL).

Figure 13.36 A worked example of calculating the maximum volume of a safe single dose of local anaesthetic²⁵

A 70 kg patient requires a local anaesthetic for a dental procedure. Lidocaine 2% (20 mg/mL) with adrenaline (epinephrine) 1:80 000 (12.5 micrograms/mL) will be used [NB1].

Calculate the maximum dose in milligrams based on the patient’s weight
- maximum safe single dose of lidocaine with adrenaline is 7 mg/kg
- 7 mg/kg $\times$ 70 kg = 490 mg
Use the concentration of solution (mg/mL) to convert the calculated dose to volume
- 490 mg $\div$ 20 mg/mL = 24.5 mL
Convert the calculated volume to number of 2.2 mL dental cartridges [NB2]
- 24.5 mL $\div$ 2.2 mL/cartridge = 11 cartridges

Therefore, the total volume administered must not exceed 24.5 mL or 11 cartridges containing 2.2 mL each.

NB1: To convert a percentage concentration to mg/mL, multiply by 10 (eg 2% = 20 mg/mL).
NB2: Dental cartridges are available in a variety of volumes (eg 1.7 mL, 1.8 mL, 2.2 mL).

Maximum Dosage Table²⁶

Local Anaesthetic	Concentration	Adrenaline (Epinephrine)	Maximum mg/kg Dose	Approximate Maximum Volume for 70 kg Adult	Approximate Maximum Volume for 20 kg Child
Lidocaine	2% (20 mg/mL)	1:80,000 (12.5 mcg/mL)	7 mg/kg	24.5 mL	7 mL
Mepivacaine	2% (20 mg/mL)	1:100,000 (10 mcg/mL)	Not specified	See below	See below
Mepivacaine (Child)	3% (30 mg/mL)	Aust product information Child (3–6 years): 1.8 mL Child (6–14 years): 2.7 mL Adolescent (14–17 years): 4.4 mL
Mepivacaine (Adolescent/Adult)	3% (30 mg/mL)	Adult: 6.6 mL
Prilocaine	3% (30 mg/mL)	Felypressin 0.03 IU/mL	9 mg/kg	21 mL	6 mL
Prilocaine (Adrenaline)	3% (30 mg/mL)	1:300,000 (3.3 mcg/mL)	9 mg/kg	21 mL	6 mL
Prilocaine (4%)	4% (40 mg/mL)	-	6 mg/kg	10.5 mL	3 mL
Articaine	4% (40 mg/mL)	1:100,000 (10 mcg/mL)	7 mg/kg	12.25 mL	3.5 mL
Articaine (1:200,000)	4% (40 mg/mL)	1:200,000 (5 mcg/mL)	7 mg/kg	12.25 mL	3.5 mL

References²⁷

Ritter JM, Flower RJ, Henderson G, Loke YK, MacEwan D, Robinson E, editors. Rang & Dale’s pharmacology. 10th ed. Edinburgh: Elsevier; 2023
Australian Medicines Handbook Online [Internet]. Adelaide (AU): Australian Medicines Handbook Pty Ltd;2000. Analgesics; [updated 2025; cited 2025]. Available from: UWA Onesearch
Australian Medicines Handbook Online [Internet]. Adelaide (AU): Australian Medicines Handbook Pty Ltd;2000. Immunomodulators and anti-inflammatories; [updated 2025; cited 2025]. Available from: UWA Onesearch
Oral and Dental Expert Group. Therapeutic Guidelines Oral and Dental (Version 3). Therapeutic Guidelines Ltd:2019
Pharmaceutical Society of Australia. Australian Pharmaceutical Formulary and Handbook: A Guide to Best Practice. 25th ed. Canberra: Pharmaceutical Society of Australia; 2021
MIMS Australia. eMIMSelite: Consumer medicine information, specific clinical monograph [Internet]. Sydney: MIMS Australia; [updated 2025; cited 2025 Apr 17]. Available from: UWA Onesearch
Malamed SF. Handbook of local anesthesia. 6th ed. St. Louis (MO): Elsevier Mosby; 2013

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L17 Analgesics and LA 2025 (1)_formatted_text

DENT 3005: Introduction to Pharmacology1

Drugs for pain relief

Acknowledgement of country2

Learning Outcomes3

Learning objectives

Pain4

Type

Severity

Pain Scales

Duration

Acute Vs chronic5

Pain Management Principles6

Start early

Route of administration

Additional considerations

The WHO analgesic ladder7

Additional considerations

Pain types and analgesia8

Orofacial pain9

Non-opioid analgesics10

Paracetamol

Dosage

NSAIDs (Non-Steroidal Anti-Inflammatory Drugs)11

Opioid analgesics12

Opioid Analgesics List

Opioids in a Nutshell13

Therapeutic guide: analgesic regimen14

Local Anesthetics15

Introduction

History

General Vs Local Anesthesia16

Local Anesthetics: MOA and Types17

Local Anesthetics: Indications and Techniques18

Local complications of local anaesthesia19

Systemic toxicity of local anaesthetics20

Local Anesthetics & vasoconstrictors21

Local Anesthetic Preparations22

Dosages in dentistry23

Calculating Maximum Safe Volume24

Figure 13.36 A worked example of calculating the maximum volume of a safe single dose of local anaesthetic25

Maximum Dosage Table26

References27

Footnotes

Graph View

Table of Contents

DENT 3005: Introduction to Pharmacology¹

Acknowledgement of country²

Learning Outcomes³

Pain⁴

Acute Vs chronic⁵

Pain Management Principles⁶

The WHO analgesic ladder⁷

Pain types and analgesia⁸

Orofacial pain⁹

Non-opioid analgesics¹⁰

NSAIDs (Non-Steroidal Anti-Inflammatory Drugs)¹¹

Opioid analgesics¹²

Opioids in a Nutshell¹³

Therapeutic guide: analgesic regimen¹⁴

Local Anesthetics¹⁵

General Vs Local Anesthesia¹⁶

Local Anesthetics: MOA and Types¹⁷

Local Anesthetics: Indications and Techniques¹⁸

Local complications of local anaesthesia¹⁹

Systemic toxicity of local anaesthetics²⁰

Local Anesthetics & vasoconstrictors²¹

Local Anesthetic Preparations²²

Dosages in dentistry²³

Calculating Maximum Safe Volume²⁴

Figure 13.36 A worked example of calculating the maximum volume of a safe single dose of local anaesthetic²⁵

Maximum Dosage Table²⁶

References²⁷