Imiquimod | Pharmacology Mentor

Generic Name

Imiquimod

TLR7 activation on Langerhans and dermal dendritic cells → downstream signaling via MyD88 → NF‑κB & IRF7 pathways.
Induction of pro‑inflammatory cytokines: TNF‑α, IFN‑α, IFN‑γ, IL‑6, IL‑8.
Enhances NK‑cell cytotoxicity and promotes antigen‑specific CD8⁺ T‑cell responses.
In viral plaques (HPV) & tumors (actinic keratosis, superficial basal‑cell carcinoma) the cytokine milieu *inhibits viral replication* and *induces apoptosis of dysplastic cells*.

Parameter	Description
Absorption	Limited systemic absorption (<1 % of applied dose); peak plasma concentrations < 0.5 ng/mL.
Distribution	Primarily local dermal; protein binding ~70 %.
Metabolism	Hepatic via CYP3A4; extensive first‑pass.
Elimination	Urine (≈90 %) and feces; half‑life ~11 h (blood).
Special populations	Renal impairment: no dosage adjustment required. Hepatic impairment: caution if severe disease.

External genital and anal warts (HPV) – 5 % cream applied 3 × weekly.
Intradermal warts – patient‑applied 5 % cream 3 × weekly.
Actinic keratosis (AK) – 5 % cream applied 2 × weekly for 6 weeks.
Superficial basal‑cell carcinoma (≤ 2.5 cm) – 5 % cream 5 × daily for 2 weeks (off‑label, case series).

Contraindications
Active systemic infection.
Known hypersensitivity to imiquimod or any excipient.
Warnings
Immunocompromised patients: increased risk of viral dissemination (acquired immunodeficiency syndrome, organ transplant).
Pregnancy/Breastfeeding: category C; potential teratogenicity in animal studies – avoid use unless benefits outweigh risks.
Dermatologic conditions: may exacerbate inflammatory dermatoses (psoriasis, eczema).
Concurrent therapies: avoid use near sites of radiotherapy or surgical incisions due to potential for heightened inflammation.

Indication	Application	Frequency	Duration
External genital warts	5 % cream	3 × weekly	4–12 weeks (titrated)
Intradermal warts	5 % cream	3 × weekly	4–6 weeks
Actinic keratosis	5 % cream	2 × weekly	6 weeks
Superficial BCC	5 % cream	5 × daily	2 weeks
Application technique	After cleansing, apply thin layer (1‑2 mm) to lesion + 0.5‑1 cm margin; cover with occlusive dressing if recommended. Avoid eyes, mucosa, broken skin. Leave overnight (≥ 8 h) unless occluded.
Titration	For initial reactions, start 2 × weekly for 2 weeks, then increase to 3 × weekly.

Efficacy: reassess lesion size and presence every 4–6 weeks; complete clearance often achieved after 8–12 weeks.
Safety: monitor for signs of systemic infection, potential fever, or unusual systemic symptoms.
Pregnancy/Breastfeeding: screening for pregnancy and counseling before therapy.
Dermatologic follow‑up: no routine labs needed; assess for progression to BCC or SCC when treating AK.

Titrate dosing: start with less frequent applications to mitigate cytokine flare; step‑wise intensification improves tolerability.
Adjunctive therapies: combining imiquimod with cryotherapy or laser often yields synergistic clearance and reduces overall treatment time.
Partner counselling: educate patients that genital warts can be transmitted even if treatment resolves lesions; prophylactic HPV vaccination is advisable.
Off‑label uses: case series report efficacy in early melanoma in situ and cutaneous viral infections (herpes zoster); however, data remain limited.
Drug interaction: co‑application with topical steroids or retinoids should be avoided due to additive inflammatory response.
Pregnancy planning: store formulations in a dedicated bottle to prevent accidental ingestion or contact; advise patients to avoid the drug if pregnancy is possible.
Patient instruction: instruct patients to perform hand hygiene after application and to avoid sun exposure on treated areas due to increased photosensitivity.

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• Key references

1. Mansour N. et al. *J Am Acad Dermatol.* 2008;59: 129–36.

2. Krug E. et al. *Dermatol Clin.* 2011;29: 373–81.

3. Wernly L. et al. *Clin Pharmacol Ther.* 2019;105: 1202–9.

*(All data are current as of 2026; refer to product labeling for updates.)*