Drug Listings: Enteral and Parenteral

Opioids – mainly for severe pain

Paracetamol

Non-steroidal anti-inflammatory drugs for mild to moderate pain relief

Approach to oral combination analgesics

Local anaesthetics

Bibliography

Note:
That while examples of generic drugs are listed below, the list should not be considered comprehensive. Drugs are regularly added and removed by pharmaceutical companies and the latest drug indices should be consulted if necessary.

Opioids – mainly for severe pain

Opioids are grouped into the following categories:

1. Opioid agonists
2. Opioid antagonists
3. Opioid dualists – with agonist and antagonist properties, theoretically cancelling side effects
4. Atypical opioids

Side effects of all opioids include the following:

1. Respiratory depression – opioid patches should not be used for acute pain
2. Sedation (best indicator of incipient respiratory depression)
3. Nausea and vomiting
4. Constipation
5. Pruritis
6. Tolerance
7. Addiction

Table I: Relevant information on opioid administration (mainly for severe pain) in adults

bd – twice daily, PCA – patient-controlled analgesia, p.o. – per os (orally), IM – intramuscular, IV – intravenous, SSRIs – selective serotonin reuptake inhibitors, SR – slow-release

Table I: Relevant information on opioids (continued)

IM – intramuscular, IV – intravenous, USE – safe, UWECO – use with extreme caution, may be unsafe, AVOID – unsafe, MAOIs – monoamine oxidase inhibitors

Table I: Relevant information on opioids (continued)

Table I: Relevant information on opioids (continued)

IM – intramuscular, IV – intravenous, MAOIs – monoamine oxidase inhibitors, SSRIs – selective serotonin reuptake inhibitors, USE – safe, SR – slow-release, NRI – noradrenaline reuptake

Paracetamol

• Excessive dosage may cause irreversible liver failure.
• Use with caution or decrease the dose for the following:
  • Acute liver disease
  • Alcohol-related liver disease
  • Glucose-6-phosphate dehydrogenase deficiency

Table II: Relevant information on paracetamol

N/A – not applicable, USE – safe, UWC – use with caution, UWECO – use with extreme caution, may be unsafe, AVOID – unsafe

Non-steroidal anti-inflammatory drugs for mild to moderate pain relief

NSAIDs can be divided into the following categories:

1. COX inhibitors
2. Selective COX-2 inhibitors
3. Specific COX-2 inhibitors

Side effects of NSAIDs include:

1. Renal damage, especially if prior renal impairment or hypovolaemia
2. Platelet impairment
3. Gastric erosions and haemorrhage
4. Possible poor wound healing
5. Asthma may be exacerbated in some patients

Sole drug for parenteral administration is parecoxib.

Table III: Relevant information on non-steroidal anti-inflammatory drugs (NSAIDs)

COX – cyclo-oxygenase, GIT – gastrointestinal tract, CNS – central nervous system, NSAIDs – nonsteroidal anti-inflammatory drugs, USE – safe, UWC – use with caution, UWECO – use with extreme caution, may be unsafe, AVOID – unsafe

Table III: Relevant information on NSAIDs (continued)

COX – cyclo-oxygenase, GIT – gastrointestinal tract, CNS – central nervous system, NSAIDs – nonsteroidal anti-inflammatory drugs, USE – safe, UWC – use with caution, UWECO – use with extreme caution, may be unsafe, AVOID – unsafe

Approach to oral combination analgesics

Combinations of all the above oral drugs are used extensively in South Africa. It is, therefore, not possible to include all combinations in this section. The rationale for drug combination is to reduce the dose of each drug and, hence, improve the side effect profile. The list below gives some components in these combination preparations and highlights specific effects or side effects.

1. Paracetamol
   • The dose is usually lower in combination preparations.
   • Always check that the patient has not received paracetamol via the intravenous (IV) or the rectal route, as overdose may occur.
2. Caffeine hydrate
   • This has a vasodilatory effect and may be good for migraines.
3. Codeine phosphate
   • This has a mild analgesic effect and has to be metabolised to morphine. In a subset of patients, excessive sedation is problematic (see above).
4. Aspirin
   • Use caution if patient has prior history of dyspepsia or bleeding diathesis.
5. Propoxyphene napsylate
   • This has a weak analgesic effect, but some sedation.
6. NSAIDs
   • Use caution if a patient has prior history of dyspepsia or bleeding diathesis and renal impairment.
7. Meprobamate
   • It is a weak analgesic.
   • Probable addiction after 10 days of use; this is a physical as well as emotional addiction.
8. Doxylamine succinate
   • There is not a clear rationale for inclusion in analgesic drugs.
9. Promethazine
   • Phenothiazine with anti-emetic and sedatory effects.
   • ‘Blackbox’ in the USA due to ↑QT interval.
10. Orphenadrine
    • This has an antimuscarinic effect.
11. Diphenhydramine
    • Antihistamine with sedatory effect (blackbox).

Table IV: Relevant information to the approach to combination analgesics

PCA – patient-controlled analgesia, LD – loading dose, MD – maintenance dose, NMDA – N-methyl-D-aspartate, USE – safe, UWC – use with caution, UWECO – use with extreme caution, may be unsafe, AVOID – unsafe

Local anaesthetics

LAs are divided into short-acting (e.g. lignocaine) or long-acting (e.g. bupivacaine, ropivacaine) anaesthetics.

The following are possible side effects:

1. Toxic doses
2. Cardiotoxicity
3. Neurotoxicity

Table V: Relevant information regarding local anaesthetics

MOF – methoxyflurane, LD – loading dose, USE – safe, UWC – use with caution, UWECO – use with extreme caution, may be unsafe, AVOID – unsafe

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South African Society of Anaesthesiologists (SASA) Guidelines for the Management of Acute Pain in Specific Scenarios 2022