CHAPTER 1
Analgesics

Kamran Ali

Qatar University, QU Health, College of Dental Medicine, Doha, Qatar

1.1 INTRODUCTION

One of the commonest presenting complaint of patients in dentistry is pain, and dentists routinely advise/prescribe analgesics. However, the main purpose of analgesics is to provide symptomatic relief before definitive treatment and minimise pain following operative interventions. Pain control during operative dental procedures is usually accomplished with administration of local anaesthesia (Chapter 3). Appropriate management of dental and orofacial pain should address the cause of pain using a comprehensive clinical assessment and relevant investigations such as radiographs. For example, patients presenting with features of pulpitis may benefit from analgesics to achieve pain relief, and definitive pain relief is best obtained through operative management of the inflamed pulp. Similarly, the use of analgesics to manage pain related to a peri‐radicular abscess can only provide a partial and temporary relief, at best. Definitive management of the abscess would require drainage of the abscess through root canal access opening or tooth extraction, as appropriate.

Some of the key principles which need to be observed when prescribing analgesics in dentistry are summarised as follows:

• Undertake a comprehensive clinical assessment

  Before advising or prescribing an analgesic, it is important to assess the source of pain along with its character, severity, site, frequency, aggravating and relieving factors to aid an accurate diagnosis.

• Choose an appropriate analgesic

  The choice of analgesic will depend on the cause and severity of pain as well as the patient's medical history and any contraindications. All medications have potential risks and benefits, and the choice of an analgesic should take into account the patient's systemic health, and any potential drug interactions of the proposed analgesics with any medications the patient may be taking.

• Determine route of administration

  In most cases, analgesics used for the management of pain in dental patients are administered orally. However, for pain associated with certain chronic conditions, such as myofascial pain and internal derangement of temporomandibular joint, topical application may be appropriate to minimise the systemic side effects associated with long‐term use of oral analgesics. Parenteral administration of analgesics for acute dental pain is usually not undertaken in general dental practice settings. Nevertheless, local anaesthetic administration can be used for immediate management of severe acute pain.

• Determine the dose and duration of analgesics cover

  Analgesics should be used at the lowest effective dose for the shortest duration necessary. This can help reduce the risk of side effects and addiction and minimise the cost. In most cases analgesics used for the management of acute dental pain are administered orally for few days until definitive management of the underlying problem. Similarly post‐operative pain following invasive dental procedures requires analgesics for up to a week. However, pain associated with certain chronic conditions such as temporomandibular joint disorders (e.g., myofascial pain and internal derangement) and trigeminal neuralgia may require long‐term analgesics. As mentioned before, topical application of analgesics may be considered if appropriate to minimise the systemic side effects associated with long‐term use of analgesics.

• Consider the cost of analgesics

  Many analgesics used in dentistry are available over the counter, and it may be much cheaper for the patients to purchase these themselves on a dentist's advice. Dispensing analgesics on a prescription may be more expensive for patients in many countries.

• Patient education and follow‐up

  Patients should be advised to read the patient information leaflet (PIL), accompanying the medication. The patients should be advised on how to take the medication safely and effectively. Also, precautions, side effects or adverse reactions to the medication and appropriate actions which may be required should be discussed. Patients should be followed up to ensure that the medication is effective and welltolerated and to make any necessary adjustments to the treatment plan.

1.2 NON‐NARCOTIC ANALGESICS

Non‐narcotic analgesics, also known as non‐steroidal anti‐inflammatory drugs (NSAIDs), are the most frequently used analgesics across the board in clinical medicine as well as dentistry. In addition to their analgesic effects, these drugs also have anti‐inflammatory, antipyretic and antiplatelet activity. These drugs are widely used for short‐term management of mild to moderate pain from various causes including dental pain. More severe pain, particularly of visceral origin, may require management with opioid analgesics either alone or in combination with NSAIDs.

1.2.1 MECHANISM OF ACTION

Tissue injury leads to breakdown of membrane phospholipids by the enzyme phospholipase A2 (). This results in the release of arachidonic acid (AA) from the membrane phospholipids. AA is metabolised via the cyclooxygenase (COX) and lipoxygenase (LOX) pathways as depicted in Figure 1.1.

Figure 1.1 Mechanism of action of non‐steroidal anti‐inflammatory drugs.

Source: Image created in BioRender.com

Most NSAIDs are non‐selective inhibitors of COX and target the two main isoforms of COX, i.e., COX‐1 and COX‐2. COX catalyses the formation of prostaglandins and thromboxane from AA. Aspirin inhibits COX irreversibly, while the other NSAIDs (e.g., indomethacin and diclofenac) cause reversible inhibition of COX. Steroids inhibit PLA2 and block both the COX and LOX pathways.

The analgesic effect results from inhibition of prostaglandin synthesis (especially inhibition of PGE2) as well as inhibition of bradykinin release from high‐molecular‐weight (HMW) kininogens in the blood plasma and tissues.

1.2.2 SIDE EFFECTS

The main side effects of NSAIDs are gastric imitation, nephrotoxicity and hypersensitivity (also see individual drugs).

1.2.3 SELECTIVE COX‐2 INHIBITORS

Traditional NSAIDs, such as aspirin, ibuprofen and naproxen, block both isoforms of COX, i.e., COX‐1 and COX‐2, which can lead to unwanted side effects such as stomach ulcers and bleeding.

COX‐2 inhibitors are a class of drugs that selectively block the enzyme cyclooxygenase‐2 (COX‐2). The rationale for using COX‐2 inhibitors is to reduce inflammation and pain without affecting the other functions of COX‐1, another form of the enzyme that is involved in the production of protective prostaglandins that help maintain the health of the stomach lining and regulate blood clotting.

However, COX‐2 inhibitors have been associated with an increased risk of cardiovascular events such as heart attack and stroke, particularly when used at high doses or for long periods of time. This has led to a sharp decline in the use of COX‐2 inhibitors. Although some COX‐2 inhibitors (e.g., celecoxib and meloxicam) may still be used for short‐term pain relief associated with conditions such as osteoarthritis, and rheumatoid arthritis, there is little indication for their use in dentistry. Extreme caution is required when using COX‐2 inhibitors in patients with cardiovascular risk factors and medical advice must be sought.

NSAIDs are used as first‐line therapy for acute dental pain. Paracetamol and ibuprofen alone or in combination are one of the most common NSAIDs used in the management of oral surgical and dental pain1–3. The following section discusses the most common oral and topical NSAIDS which are used in the management of pain and inflammation associated with oral and dental disorders.

1.3 COMMON NON‐STEROIDAL ANTI‐INFLAMMATORY AGENTS USED IN DENTISTRY

1.3.1 ASPIRIN (ACETYL SALICYLIC ACID)

• Indications: Mild to moderate pain, pyrexia, antiplatelet activity (see Chapter 15).
• Cautions: Impaired renal or hepatic function; dehydration; elderly; pregnancy; asthma, allergic disease; alcohol (gastric bleeding).
• Contra‐indications: Children under 12 years, breastfeeding, gastrointestinal ulceration, and blood dyscrasias such as haemophilia and thrombocytopenia.
• Hypersensitivity: Contraindicated in patients with hypersensitivity to aspirin or other NSAIDs; asthma; angioedema; rhinitis; urticaria.
• Side effects: GIT irritation; slight asymptomatic blood loss; increased bleeding time; bronchospasm; skin reactions in hypersensitive patients.
• Interactions: Enhances effects or oral anticoagulants (bleeding); oral hypoglycaemics (hypoglycaemia); corticosteroids (peptic ulceration).

COMMERCIAL PREPARATIONS:

• Aspirin
  • Tablets, aspirin 300 mg

ROUTE OF ADMINISTRATION AND...