Author: Dr Tim Aung, Primary Care Practitioner, Brisbane & Logan, Queensland, Australia. DermNet NZ Editor in Chief: Adjunct A/Prof Amanda Oakley, Dermatologist, Hamilton, New Zealand. Copy edited by Gus Mitchell/Maria McGivern. April 2019.
What is drug-induced pruritus?
Pruritus is the medical name for itching. Drug-induced pruritus is an itch caused or triggered by medication. There are various itchy drug eruptions, but generally, the term ‘drug-induced pruritus’ implies that no primary rash is present — just scratch marks.
- Pruritus can begin within hours or up to several weeks after the drug responsible has first been administered.
- Pruritus can be classified as acute [ie, present for < 6 weeks] or chronic [ie, present for > 6 weeks].
- It can be localised or generalised.
- Following the cessation of the causative drug, the itch may persist for days to months before resolving.
Who gets drug-induced pruritus?
The epidemiology of drug-induced pruritus is unknown. Generally, adverse drug reactions are more common in older patients and in patients taking multiple medicines.
What is the cause of drug-induced pruritus?
The cause of drug-induced pruritus is often unknown and depends on the drug. It may involve:
- A genetic predisposition
- Vasodilation
- Phototoxicity
- Neural pathways
- Cutaneous deposition of drugs or their metabolites
- Dry skin
- Cholestatic liver injury
- Another unknown mechanism [1,2].
Which drugs cause pruritus?
The most commonly reported drugs to cause pruritus are opioids [especially during spinal anaesthesia], chemotherapeutic agents, and chloroquine [affecting 60–70% of black Africans prescribed this medicine].
The main groups of drugs that cause pruritus through various mechanisms are listed below.
Antimicrobials and antibiotics
Antimicrobials and antibiotics that cause pruritus include:
- Penicillin G
- Amoxicillin/clavulanate
- Ampicillin
- Cefotaxime
- Ceftazidime
- Erythromycin
- Ciprofloxacin
- Vancomycin
- Clindamycin
- Tetracyclines
- Minocycline
- Metronidazole
- Rifampicin
- Trimethoprim/sulfamethoxazole
- Oral antifungal agents
- Antimalarial agents [chloroquine and amodiaquine]
Cardiovascular medicines
Cardiovascular medicines that can cause pruritus include:
- Amlodipine
- Diltiazem
- Verapamil
- Clonidine
- Methyldopa
- Amiodarone
- Captopril
- Enalapril
- Lisinopril
- Candesartan
- Irbesartan.
Metabolic medicines
Metabolic medicines that can cause pruritus include:
- Metformin
- Gliclazide
- Allopurinol.
Neuroleptic and psychotropic drugs
Neuroleptic and psychotropic drugs [used to treat psychosis] that can cause pruritus include:
- Amitriptyline
- Citalopram
- Fluoxetine
- Paroxetine
- Sertraline
- Carbamazepine
- Phenytoin
- Topiramate
- Chlorpromazine
- Phenothiazine
- Risperidone.
Opioids and analgesics
Opioids and analgesics that can cause pruritus include:
- Morphine
- Codeine
- Fentanyl
- Oxycodone
- Tramadol
- Aspirin.
Steroids and hormones
Steroids and hormones that can cause pruritus include:
- Danazol
- Some oral contraceptive pills.
Chemotherapeutics and biological agents
Chemotherapeutic and biological agents that can cause pruritus include:
- Chlorambucil
- Gemcitabine
- Nilotinib
- Vemurafenib
- Temsirolimus
- Ipilimumab
- Cetuximab
- Rituximab
- Panitumumab
- Gefitinib [2,6]
- The tumour necrosis factor-alpha blockers adalimumab and infliximab [7].
Other drugs
Other drugs that can cause pruritus include:
- Enoxaparin
- Hydroxyethyl starch [a plasma volume expanders]
- Radiopaque contrast agents [1–3].
What is the treatment of drug-induced pruritus?
The cessation of the causative drug is an immediate priority [1,4–6]. Treatment depends on how the causative drug triggered the itching and its severity.
- If the pruritus is associated with dry skin or secondary dermatitis, topical steroids and moisturisers may be of benefit.
- Topical capsaicin has been reported as useful for treating localised drug-induced pruritus.
- Oral antihistamines are effective if the pruritus is associated with an urticaria-like mechanism.
- Systemic corticosteroids may be effective if there is an inflammatory pathway suspected to be involved.
- Naloxone or naltrexone is used for pruritus caused by the activation of mu receptor in the nervous system [in the case of opioids and plasma volume expanders].
- Ursodeoxycholic acid and cholestyramine can reduce pruritus due to cholestatic liver injury.
- Doxepin, amitriptyline, gabapentin, paroxetine, and ondansetron can also be used as second- or third-line antipruritic agents.
- Phototherapy can also be of benefit.