Topical Drug Delivery

Concentration and Safety Considerations

The concentration of organic solvents like DMSO in formulations should not exceed 10% for any route of administration to minimize adverse reactions while maintaining efficacy, as recommended by the British Journal of Cancer guidelines 1
For experimental agents in animal studies, DMSO should not exceed 5 ml/kg or 10% of injected volume, as recommended by the British Journal of Cancer guidelines 2

The concentration and volume of DMSO are critical factors affecting both efficacy and safety, with higher concentrations causing more side effects, according to the British Journal of Cancer 1
The combination of ketamine and amitriptyline has a synergistic effect, with amitriptyline inhibiting serotonin and norepinephrine reuptake and blocking sodium channels, while ketamine blocks NMDA receptors, showing effectiveness in managing various chronic pain conditions, particularly neuropathic pain 3

DMSO is used in FDA-approved diclofenac sodium topical solution for osteoarthritis, and is approved in Europe for idoxuridine topical solution for herpes zoster treatment, with established clinical evidence supporting its use as a penetration enhancer 1
Topical DMSO is recommended as a treatment option for extravasations occurring during anthracyclines, mitomycin C, or platin salts infusion, with a strength of evidence of III, B, by the European Society for Medical Oncology 4
Topical DMSO is recommended as a treatment option for pain management, particularly for neuropathic pain, due to its ability to block conduction in peripheral nerve C fibers (pain-transmitting fibers) 4
The American College of Physicians recommends starting with 0.5% ketamine compounded with 1-2% amitriptyline, applied up to 3 times daily to affected areas for chronic pain management 3
The British Association of Dermatologists supports the use of DMSO as a penetration enhancer in photodynamic therapy (PDT) for treating basal cell carcinoma (BCC), with DMSO + EDTA increasing clinical clearance rates from 67% to 90% for nodular BCCs < 2mm thick 5
DMSO can be used in combination with 23% ALA gel and red light PDT for treating sarcoidosis, with reported histological clearance and no recurrence at 18 months, as reported by the British Journal of Dermatology 6

DMSO appears safe when used in small doses, with mostly transient adverse effects, including gastrointestinal and skin-related reactions, which are dose-dependent 1
Important considerations for DMSO use include local erythema, which may affect correct evaluation of tissue damage, and varying concentrations available in different countries, with 99% DMSO potentially causing local erythema 4
The European Society for Medical Oncology notes that most adverse reactions to DMSO are transient and mild, with a clear dose-relationship with adverse effects, and recommends starting with lower concentrations (around 50%) to minimize skin irritation 4
DMSO can cause local erythema, skin rash, and pruritus, especially at higher concentrations, and starting with lower concentrations (around 50%) is recommended to minimize skin irritation 4
The safety of DMSO in combination with other drugs has not been fully established, with reported neurotoxic interactions with sulindac 4
Open wounds or broken skin at application site, known hypersensitivity to ketamine or amitriptyline, and caution in patients with severe cardiovascular disease are contraindications or precautions for topical ketamine use 3

Assess pain relief, functional improvement, and adverse effects at 2-4 weeks, and if no improvement after 4-6 weeks of optimized therapy, consider alternative treatments 3
Document baseline pain scores and reassess regularly using validated pain scales 3