Methoxsalen

PSORIASIS THERAPY

1.    DRUG DOSAGE -INITIAL THERAPY: Methoxsalen capsules should be taken 1-1/2 to 2 hours before UVA exposure with some low-fat food or milk according to the following table:

Geriatric patients should generally be started at the low end of the dose recommended according to body weight and closely monitored during PUVA therapy. Although clinical experience has not identified differences in response between elderly and younger patients, the use of methoxsalen in older individuals may be affected by the presence of pre-existing medical conditions.

2. INITIAL EXPOSURE: The initial UVA exposure energy level and corresponding time of exposure is determined by the patient's skin characteristics for sun burning and tanning as follows:

If the MPD is done, start at 1/2 MPD.

Additional drug dosage directions are as follows:

Weight Change: In the event that the weight of a patient changes during treatment such that he/she falls into an adjacent weight range/dose category, no change in the dose of methoxsalen is usually required. If, in the physician's opinion, however, a weight change is sufficiently great to modify the drug dose, then an adjustment in the time of exposure to UVA should be made.

Dose/Week: The number of doses per week of methoxsalen capsules will be determined by the patient's schedule of UVA exposures. In no case should treatments be given more often than once every other day because the full extent of phototoxic reactions may not be evident until 48 hours after each exposure.

Dosage Increase: Dosage may be increased by 10 mg. after the 15th treatment under the conditions outlined in section XI.B.4.b.

X. UVA RADIATION SOURCE SPECIFICATIONS AND INFORMATION

A. IRRADIANCE UNIFORMITY

The following specifications should be met with the window of the detector held in a vertical plane:

Vertical Variation: For readings taken at any point along the vertical center axis of the chamber (to within 15 cm from the top and bottom), the lowest reading should not be less than 70 % of the highest reading.

Horizontal Variation: Throughout any specific horizontal plane, the lowest reading must be at least 80 % of the highest reading, excluding the peripheral 3 cm of the patient treatment space.

B. PATIENT SAFETY FEATURES:

The following safety features should be present: (1) Protection from electrical hazard: All units should be grounded and conform to applicable electrical codes. The patient or operator should not be able to touch any live electrical parts. There should be ground fault protection. (2) Protective shielding of lamps: The patient should not be able to come in contact with the bare lamps. In the event of lamp breakage, the patient should not be exposed to broken lamp components. (3) Hand rails and hand holds: Appropriate supports should be available to the patient. (4) Patient viewing window: A window which blocks UV should be provided for viewing the patient during treatment. (5) Door and latches: Patients should be able to open the door from the inside with only slight pressure to the door. (6) Non-skid floor: The floor should be of a non-skid nature. (7) Thermoregulation: Sufficient air flow should be provided for patient safety and comfort, limiting temperature within the UVA radiator cabinet to approximately less than 100 °F. (8) Timer: The irradiator should be equipped with an automatic timer which terminates the exposure at the conclusion of a pre-set time interval. (9) Patient alarm device: An alarm device within the UVA irradiator chamber should be accessible to the patient for emergency activation. (10) Danger label: The unit should have a label prominently displayed which reads as follows:

DANGER - Ultraviolet radiation - Follow your physicians instructions - Failure to use protective eyewear may result in eye injury.

C. UVA EXPOSURE DOSIMETRY MEASUREMENTS:

The maximum radiant exposure or irradiance (within ±15%) of UVA (320-400 nm) delivered to the patient should be determined by using an appropriate radiometer calibrated to be read in J/cm2 or mW/cm2. In the absence of a standard measuring technique approved by the National Bureau of Standards, the system should use a detector corrected to a cosine spatial response. The use and recalibration frequency of such a radiometer for a specific UVA irradiator chamber should be specified by the manufacturer because the UVA dose (exposure) is determined by the design of the irradiator, the number of lamps, and the age of the lamp. If irradiance is measured, the radiometer reading in mW/cm2 is used to calculate the exposure time in minutes to deliver the required UVA in J/cm2 to a patient in the UVA irradiator cabinet. The equation is:

Exposure Time         Desired UVA Dose (J/cm2)

  (minutes)          =  -------------------------------------

                                   0.06 x Irradiance (mW/cm2)

Overexposure due to human error should be minimized by using an accurate automatic timing device, which is set by the operator and controlled by energizing and de-energizing the UVA irradiator lamp. The timing device calibration interval should be specified by the manufacturer. Safety systems should be included to minimize the possibility of delivering a UVA exposure which exceeds the prescribed dose, in the event the timer or radiometer should malfunction.

D. UVA SPECTRAL OUTPUT DISTRIBUTION:

The spectral distributions of the lamps should meet the following specifications:

XI. PUVA TREATMENT PROTOCOL:

INTRODUCTION:

The Methoxsalen Capsules, USP 10 mg [Soft Gelatin Capsules] reach their maximum bioavailability in 1-1/2 to 2 hours after ingestion.

On average, the serum level achieved with Methoxsalen Capsules, USP 10 mg [Soft Gelatin Capsules] is twice that obtained with hard gelatin capsules and reach their peak concentration in less than half the time of the hard gelatin capsules.

As a result the mean MED J/cm2 for the Methoxsalen Capsules, USP 10 mg [Soft Gelatin Capsules] is substantially less than that required for hard gelatin capsules (Levins et al., 1984 and private communication1).

Photosensitivity studies demonstrate a shorter time of peak photosensitivity of 1.5 to 2.1 hours vs. 3.9 to 4.25 hours for regular methoxsalen capsules.

A. INITIAL EXPOSURE:

The initial UVA exposures should be conducted according to the guidelines presented previously under IX. Psoriasis therapy, Drug dosage-initial Therapy and initial Exposure.

B. CLEARING PHASE:

Specific recommendations for patient treatment are as follows:

SKIN TYPES I, II, & III. Patients with skin types I, II, and III may be treated 2 or 3 times per week. UVA exposure may be held constant or increased by up to 1.0 J/cm2 at each treatment, according to the patient's response. If erythema occurs, however, do not increase exposure time until erythema resolves. The severity and extent of the patient's erythema may be used to determine whether the next exposure should be shortened, omitted, or maintained at the previous dosage. (See ADVERSE REACTIONS.)

SKIN TYPES IV, V, & VI. Patients with skin types IV, V, and VI may be treated 2 or 3 times per week. UVA exposure may be held constant or increased by up to 1.5 J/cm2 at each treatment unless erythema occurs. If erythema occurs, follow instructions outlined above in the procedures for patients with skin types I, II, and III.

ERYTHRODERMIC PSORIASIS. Patients with erythrodermic psoriasis should be treated with special attention because pre-existing erythema may obscure observations of possible treatment-related phototoxic erythema. These patients may be treated 2 or 3 times per week, as a Type I patient.

MISCELLANEOUS SITUATIONS:

If there is no response after a total of 10 treatments, the exposure of UVA energy may be increased by an additional 0.5–1.0 J/cm2 above the prior incremental increases for each treatment. (Example: a patient whose exposure dosage is being increased by 1.0 J/cm2 may now have all subsequent doses increased by 1.5–2.0 J/cm2.)

If there is no response, or only minimal response, after 15 treatments, the dosage of methoxsalen may be increased by 10 mg (a one-time increase in dosage). This increased dosage may be continued for the remainder of the course of treatment but should not be exceeded.

If a patient misses a treatment, the UVA exposure time of the next treatment should not be increased. If more than one treatment is missed, reduce the exposure by 0.5 J/cm2 for each treatment missed.

If the lower extremities are not responding as well as the rest of the body and do not show erythema, cover all other body areas and give 25 % of the present exposure dose as an additional exposure to the lower extremities. This additional exposure to the lower extremities should be terminated if erythema develops on these areas.

Non-responsive psoriasis: If a patient's generalized psoriasis is not responding, or if the condition appears to be worsening during treatment, the possibility of a generalized phototoxic reaction should be considered. This may be confirmed by the improvement of the condition following temporary discontinuance of this therapy for two weeks. If no improvement occurs during the interruption of treatment, this patient may be considered a treatment failure.

C. ALTERNATIVE EXPOSURE SCHEDULE:

As an alternative to increasing the UVA exposure at each treatment, the following schedule may be followed; this schedule may reduce the total number of J/cm2 received by the patient over the entire course of therapy.

Incremental increases in UVA exposure for all patients may range from 0.5 to 1.5 J/cm2, according to the patient's response to therapy.

Once Grade 2 clearing (see Table 2) has been reached and the patient is progressing adequately, UVA dosage is held constant. This dosage is maintained until Grade 4 clearing is reached.

If the rate of clearing significantly decreases, exposure dosage may be increased at each treatment (0.1-1.5 J/cm2) until Grade 3 clearing and a satisfactory progress rate is attained. The UVA exposure will be held constant again until Grade 4 clearing is attained. These increases may be used also if the rate of clearing significantly decreases between Grade 3 and Grade 4 response. However, the possibility of a phototoxic reaction should be considered; see Non-responsive Psoriasis, above.

In summary, this schedule raises slightly the increments (J/cm2) of UVA dosage, but limits these increases to those periods when the patient is not responding adequately. Otherwise, the UVA exposure is held at the lowest effective dose.

D. MAINTENANCE PHASE:

The goal of maintenance treatment is to keep the patient as symptom-free as possible with the least amount of UVA exposure.

SCHEDULE OF EXPOSURES: When patients have achieved 95% clearing, or Grade 4 response (Table 2), they may be placed on the following maintenance schedules (M1 – M4), in sequence. It is recommended that each maintenance schedule be adhered to for at least 2 treatments (unless erythema or psoriatic flare occurs, in which case see (2a) and (2b) below).

LENGTH OF EXPOSURE: The UVA exposure for the first maintenance treatment of any schedule (except M4 as noted below) is the same as that of the patient's last treatment under the previous schedule. For skin types I–IV, however, it is recommended that the maximum UVA dosage during maintenance treatments not exceed the following:

If the patient develops erythema or new lesions of psoriasis, proceed as follows: a. Erythema: During maintenance therapy, the patient's tan and threshold dose for erythema may gradually decrease. If maintenance treatments produce significant erythema, the exposure to UVA should be decreased by 25% until further treatments no longer produce erythema.

b. Psoriasis: If the patient develops new areas of psoriasis during maintenance therapy (but still is classified as having a Grade 4 response), the exposure to UVA may be increased by 0.5-1.5 J/cm2 at each treatment; this is appropriate for all types of patients. These increases are continued until the psoriasis is brought under control and the patient is again clear. The exposure being administered when this clearing is reached should be used for further maintenance treatment.

FLARES DURING MAINTENANCE: If the patient flares during maintenance treatment (i.e., develops psoriasis on more than 5% of the originally involved areas of the body), this maintenance treatment schedule may be changed to the preceding maintenance or clearing schedule. The patient may be kept on his schedule until again 95 % clear. If the original maintenance treatment schedule is unable to control the psoriasis, the schedule may be changed to a more frequent regimen. If a flare occurs less than 6 weeks after the last treatment, 25 % of the maximum exposure received during the clearing phase, with the clearing schedule received during the clearing phase, may be used and then proceed with the clearing schedule previously followed for this patient. (At 95% clearing, follow regular maintenance until the optimum maintenance schedule is determined for the patient.) If more than 6 weeks have elapsed since the last treatment was given, treat patients as if they were beginning therapy insofar as exposure dosages are concerned, since their threshold for erythema may have decreased.

A. METHOXSALEN:

The most commonly reported side effect of methoxsalen alone is nausea, which occurs with approximately 10% of all patients. This effect may be minimized or avoided by instructing the patient to take methoxsalen in milk or food, or to divide the dose into two portions, taken approximately one-half hour apart. Other effects include nervousness, insomnia, and depression.

B. COMBINED METHOXSALEN/UVA THERAPY:

PRURITUS: This adverse reaction occurs with approximately 10% of all patients. In most cases, pruritus can be alleviated with frequent application of bland emollients or other topical agents; severe pruritus may require systemic treatment. If pruritus is unresponsive to these measures, shield pruritic areas from further UVA exposure until the condition resolves. If intractable pruritus is generalized, UVA treatment should be discontinued until the pruritus disappears.

ERYTHEMA: Mild, transient erythema at 24-48 hours after PUVA therapy is an expected reaction and indicates that a therapeutic interaction between methoxsalen and UVA occurred. Any area showing moderate erythema (greater than Grade 2 - See Table 1 for grades of erythema) should be shielded during subsequent UVA exposures until the erythema has resolved. Erythema greater than Grade 2 which appears within 24 hours after UVA treatment may signal a potentially severe burn. Erythema may become progressively worse over the next 24 hours, since the peak erythemal reaction characteristically occurs 48 hours or later after methoxsalen ingestion. The patient should be protected from further UVA exposures and sunlight, and should be monitored closely.

IMPORTANT DIFFERENCES BETWEEN PUVA ERYTHEMA AND SUNBURN: PUVA-induced inflammation differs from sunburn or UVB phototherapy in several ways. The % transmission of UVB varies between 0% to 34% through skin whereas UVA varies between 1% to 80% transmission; thus, UVA is transmitted to a larger % through the skin. (Diffey, 198222). The DNA lesions induced by PUVA are very different from UV-induced thymine dimers and may lead to a DNA crosslink. This DNA lesion may be more problematic to the cell because crosslinks are more lethal and psoralen-DNA photoproducts may be "new" or unfamiliar substrates for DNA repair enzymes. DNA synthesis is also suppressed longer after PUVA. The time course of delayed erythema is different with PUVA and may not involve the usual mediators seen in sunburn. PUVA-induced redness may be just beginning at 24 hours, when UVB erythema has already passed its peak. The erythema dose-response curve is also steeper for PUVA. Compared to equally erythemogenic doses of UVB, the histologic alterations induced by PUVA show more dermal vessel damage and longer duration of epidermal and dermal abnormalities.

OTHER ADVERSE REACTIONS: Those reported include edema, dizziness, headache, malaise, depression, hypopigmentation, vesiculation and bullae formation, non-specific rash, herpes simplex, miliaria, urticaria, folliculitis, gastrointestinal disturbances, cutaneous tenderness, leg cramps, hypotension, and extension of psoriasis.

To report SUSPECTED ADVERSE REACTION, contact Strides Pharma Inc. at 1-877-244-9825 or go to www.strides.com or FDA at 1-800-FDA-1088 or www.fda.gov/medwatch.

A. SKIN BURNING:

Serious burns from either UVA or sunlight (even through window glass) can result if the recommended dosage of the drug and/or exposure schedules are exceeded.

B. CARCINOGENICITY:

ANIMAL STUDIES: Topical or intraperitoneal methoxsalen has been reported to be a potent photocarcinogen in albino mice and hairless mice (Hakim et al., 196010). However, methoxsalen given by the oral route to Swiss albino mice suggests this agent exerts a protective effect against ultraviolet carcinogenesis; mice given 8-methoxypsoralen in their diet showed 38% ear tumors 180 days after the start of ultraviolet therapy compared to 62% for controls (O'Neal et al., 195711).

HUMAN STUDIES: A 5.7 year prospective study of 1380 psoriasis patients treated with oral methoxsalen and ultraviolet A photochemotherapy (PUVA) demonstrated that the risk of cutaneous squamous-cell carcinoma developing at least 22 months following the first PUVA exposure was approximately 12.8 times higher in the high dose patients than in the low dose patients (Stern et al., 197912, Stern et al., 198013, and Stern et al., 198414). The substantial dose-dependent increase was observed in patients with neither a prior history of skin cancer nor significant exposure to cutaneous carcinogens. Reduction in PUVA dosage significantly reduces the risk. No substantial dose-related increase was noted for basal cell carcinoma according to Stern et al., 198414. Increases appear greatest in patients who have pre-PUVA exposure to 1) prolonged tar and UVB treatment, 2) ionizing radiation, or 3) arsenic. Roenigk et al., 198015, studied 690 patients for up to 4 years and found no increase in the risk of non-melanoma skin cancer, although patients in this cohort had significantly less exposure to PUVA than in the Stern et al. study. Recent analysis of new data in the Stern et al cohort (Stern et al., 199716) has shown that these patients have an elevated relative risk of contracting melanoma. The relative risk for melanoma in these patients was 2.3 (95% confidence interval 1.1 to 4.1). The risk is particularly higher in those patients who have received more than 250 PUVA treatments and in those whose treatment has spanned greater than 15 years earlier. Some patients developing melanoma did so even after having ceased PUVA therapy over 5 years earlier. These observations indicate the need for monitoring of PUVA patients for skin tumors throughout their lives. In a study in Indian patients treated for 4 years for vitiligo, 12% developed keratoses, but not cancer, in the depigmented, vitiliginous areas (Mosher, 198017). Clinically, the keratoses were keratotic papules, actinic keratosis-like macules, nonscaling dome-shaped papules, and lichenoid porokeratotic-like papules.

C. CATARACTOGENICITY:

ANIMAL STUDIES: Exposure to large doses of UVA causes cataracts in animals, and this effect is enhanced by the administration of methoxsalen (Cloud et al., 196018; Cloud et al., 196119 Freeman et al., 196920).

HUMAN STUDIES: It has been found that the concentration of methoxsalen in the lens is proportional to the serum level. If the lens is exposed to UVA during the time methoxsalen is present in the lens, photochemical action may lead to irreversible binding of methoxsalen to proteins and the DNA components of the lens (Lerman et al., 198021). However, if the lens is shielded from UVA, the methoxsalen will diffuse out of the lens in a 24-hour period (Lerman et al., 198021). Patients should be told emphatically to wear UVA absorbing, wrap-around sunglasses for the 24-hour period following ingestion of methoxsalen whether exposed to direct or indirect sunlight in the open or through a window glass. Among patients using proper eye protection, there is no evidence for a significantly increased risk of cataracts in association with PUVA therapy (Stern et al., 197912). Thirty-five of 1380 patients have developed cataracts in the 5 years since their first PUVA treatment. This incidence is comparable to that expected in a population of this size and age distribution. No relationship between PUVA dose and cataract risk in this group has been noted.

D. ACTINIC DEGENERATION:

Exposure to sunlight and/or ultraviolet radiation may result in "premature aging" of the skin.

E. BASAL CELL CARCINOMAS:

Patients exhibiting multiple basal cell carcinomas or having a history of basal cell carcinomas should be diligently observed and treated.

F. RADIATION THERAPY:

Patients having a history of previous x-ray therapy or grenz ray therapy should be diligently observed for signs of carcinoma.

G. ARSENIC THERAPY:

Patients having a history of previous arsenic therapy should be diligently observed for signs of carcinoma.

H. HEPATIC DISEASES:

Patients with hepatic insufficiency should be treated with caution since hepatic biotransformation is necessary for drug urinary excretion.

I. CARDIAC DISEASES:

Patients with cardiac diseases or others who may be unable to tolerate prolonged standing or exposure to heat stress should not be treated in a vertical UVA chamber.

J. GERIATRIC PATIENTS:

Caution should be used in elderly patients, especially those with a pre-existing history of cataracts, cardiovascular conditions, kidney and/or liver dysfunction, or skin cancer.

K. TOTAL DOSAGE:

The total cumulative dose of UVA that can be given over long periods of time with safety has not as yet been established.

L. CONCOMITANT THERAPY:

Special care should be exercised in treating patients who are receiving concomitant therapy (either topically or systemically) with known photosensitizing agents such as anthralin, coal tar or coal tar derivatives, griseofulvin, phenothiazines, nalidixic acid, fluoroquinolone antibiotics, halogenated salicylanilides (bacteriostatic soaps), sulfonamides, tetracyclines, thiazides and certain organic staining dyes such as methylene blue, toluidine blue, rose bengal, and methyl orange.