DIETHYLCARBAMAZINE

Pharmacology and mechanism of action

Diethylcarbamazine (DEC) is a piperazine derivative which was introduced in clinical medicine in 1947. The drug is active against adult and microfilariae forms of Wuchereria bancrofti, Brugia malayi, Brugia timori and Loa loa. Against Onchocerca volvulus, the drug is only effective against the microfilariae. Soon after its administration, it causes rapid disappearance of microfilariae from the blood (lymphatic filariasis) or from the skin (onchocerciasis). Its effect against microfilariae in nodules or in hydroceles and in advanced elephantiasis is minimal ^[1].
The mechanism of action of DEC is not well understood. The drug has no microfilaricidal effect in vitro ^[2]. In vivo, the microfilariae is first immobilized by the drug due to a possible hyperpolarization of the worm. This is followed by changes on the outer surface of the microfilariae making them more susceptible to the host’s defence system^[3]. More recently, the drug has been reported to inhibit microtubule polymerization and disrupt preformed microtubule protein prepared from porcine brain in vitro ^[4]. The relevance of this action in the living parasite remains to be studied. A similar mechanism of action has been described for benzimidazoles (see Mebendazole, p. 78).

Indications

DEC is used for the treatment of individual cases infected by Wuchereria bancrofti, Brugia malayi, B. timori andLoa loa. It may also be used for large scale chemotherapeutic control of filariasis. DEC is also used in Acanthocheilonema streptocerca infestations and in tropical eosinophilia.
In onchocerciasis, DEC should only be used when ivermectin is not available.

Side effects

Side effects related to DEC are usually mild and include headache, general weakness, joint pains, anorexia, nausea and vomiting. They are dose-dependent. There are specific side effects seen only in patients with filariasis. They are assumed to be caused by antigens released by dying microfilariae. In lymphatic filariasis, the side effect; are usually mild. However, in onchocerciasis, the reaction to treatment with DEC may become quite severe. The reaction is known as the ‘Mazzotti’ after its original descriptior and has been used as a diagnostic test for the disease ^[5]. It occurs in two phases. A primary phase which commences within 24 hours and manifests as a variable combination of increased itching of the skin and eyes, photophobia, lacrimation, erythema and oedema of the skin and conjunctiva, lymphangitis, chills, anxiety, sweating and syncope. Respiratory distress, hyperpyrexia, hypotension, tachycardia and headache can also occur. Reversible proteinuria may be seen. A second phase may follow 2–6 days later with severe symmetrical acute polyarthritis predominantly in the knees, ankles, wrists, the interphalangeal joints and the shoulders. It is usually accompanied by a recrudescence of fever. The severity of Mazzotti reaction is related chiefly to the number of microfilariae killed ^[6].
To be able to quantify the severity of the reaction a scoring system has been developed ^[7]. Using this scoring system, the suppressive effects of cyproheptadine, indomethacin, prednisolone, and their combinations on the reaction were evaluated. A marked suppression of the mean total reaction score occurred only in the group treated with the full course of prednisone.
Prednisone, however, had little effect on the severity of the itching and did not prevent the occurrence of the acute febrile polyarthritis of the secondary reaction. Prednisone has also significantly impaired the therapeutic effect of DEC ^[8-10].
Treatment may aggravate ocular lesions and precipitate blindness as a result of the reaction against the dead and dying microfilariae. A pre-treatment eye examination is advisable in cases with a high microfilarial density in a biopsyfrom epicanthus or from other locations.
Encephalitis and retinal damage may occur in patients with loaiasis. Periarticular swellings (‘Calabar swelling’) due to a local reaction around the dying worm are also frequently seen in such patients.

Contraindications and precautions

There are no known contraindications to the drug. Dosage should be reduced in patients with renal impairment^[11] or in strict vegetarians with high urinary pH^[12] since renal function and pH are important factors for the excretion of the drug. Dosage may also be reduced in patients in poor general condition or who are heavily infected.

Preparations

Available as diethylcarbamazine citrate: 100 mg citrate is approximately equivalent to 50 mg base.
• Banocide® (Wellcome) Oral solution 10 mg/ml and 24 mg/ml; tablets 50 mg, 100 mg.
• Hetrazan® (Lederle) Tablets 50 mg.
• Notezine® (Specia) Tablets 50 mg.

References

1. Webster LT (1990). Chemotherapy of parasitic infections. In: Goodman & Gilman’s The Pharmacological basis of Therapeutics, 8th edn, edited by A.G.Gilman, T.W.Rall, A.S.Nies and P. Taylor (New York: Pergamon Press) pp. 960–961.
2. Langham ME, Kramer TR (1980). The in vitro effect of diethylcarbamazine on the motility and survival of Onchocerca volvulus microfilariae. Tropenmed Parasitol, 31, 155–158.
3. Allen GD, Goodchild TM, Weatherley BC (1979). Determination of 1-diethylcarbamoyl-4methylpiperazine in human plasma and urine. J Chromatogr, 164, 521–526.
4. Edwards G, Awadzi K, Breckenridge AM, Gilles HM, L’E Orme M, Ward SA (1981). Diethylcarbamazine disposition in patients with onchocerciasis. Clin Pharmacol Ther, 30, 551–557.
5. Mazzotti L (1948). Posibilidad de utilizar como medio diagnóstico auxiliar en la oncocercosis las reacciones alérgicas consecutivas a la administración del ‘Heterzán’. Revista del Instituto Salubridad Enfermedades Tropicales, 9, 235–237.
6. Awadzi K, Gilles HM (1992). Diethylcarbamazine in the treatment of patients with onchocerciasis. Br J Clin Pharmacol, 34, 281–288.
7. Awadazi K (1980). The chemotherapy of onchocerciasis. II. Quantification of the clinical reaction to microfilaricides. Ann Trop Med Parasitol, 74, 189–197.
8. Awadzi K, Orme ML’E, Breckenridge AM, Gilles HM (1982). The chemotherapy of onchocerciasis VI. The effects of indomethacin and cyproheptadin on the Mazzotti reaction. Ann Trop Med Parasitol, 76, 323–330.
9. Awadzi K, Orme ML’E, Breckenridge AM, Gilles HM (1982). The chemotherapy of onchocerciasis VII. The effect of prednisone on the Mazzotti reaction. Ann Trop Med Parasitol, 76, 331–338.
10. Awadzi K, Orme ML’E, Breckenridge AM, Gilles HM (1982). The chemotherapy of onchocerciasis IX: The effect of prednisone plus cyproheptadine on the Mazzotti reaction. Ann Trop Med Parasitol, 76, 547–555.
11. Adjepon-Yamoah KK, Edwards G, Breckenridge AM, Orme ML’E, Ward SA (1982). The effect of renal disease on the pharmacokinetics of diethylcarbamazine in man. Br J Clin Pharmacol, 13, 829–834.
12. Edwards G, Breckenridge AM, Adjepon-Yamoah KK, Orme ML’E, Ward SA (1981). The effect of variations in urinary pH on the pharmacokinetics of diethylcarbamazine. Br J Clin Pharmacol, 12, 807–812.

Description

Discovered in the 1940s, diethylcarbamazine (DEC) has proven to be especially effective as a filaricidal agent. The incidence of filariasis among American troops during World War II necessitated a search for drugs with an antifalarial spectrum of activity. The once-popular piperazine also was discovered during these initial screenings. Although chemically similar, the activity again helminths is quite different. Piperazine is active against nematodes, whereas DEC is active against falaria and microfalaria.

Originator

Hetrazan,Lederle,US,1949

Indications

Diethylcarbamazine citrate (Hetrazan) is active against several microfilaria and adult filarial worms. It interferes with the metabolism of arachidonic acid and blocks the production of prostaglandins, resulting in capillary vasoconstriction and impairment of the passage of the microfilaria. Diethylcarbamazine also increases the adherence of microfilariae to the vascular wall, platelets, and granulocytes.
Diethylcarbamazine is absorbed from the gastrointestinal tract, and peak blood levels are obtained in 4 hours; the drug disappears from the blood within 48 hours. The intact drug and its metabolites are excreted in the urine.
Diethylcarbamazine is the drug of choice for certain filarial infections, such as Wuchereria bancrofti, Brugia malayi and Loa loa. Since diethylcarbamazine is not universally active against filarial infections, a specific diagnosis based on blood smears, biopsy samples, and a geographic history is important. Dosage should be adjusted in patients with renal impairment.
Caution is necessary when using this agent, particularly when treating onchocerciasis.The sudden death of the microfilariae can produce mild to severe reactions within hours of drug administration. These are manifested by fever, lymphadenopathy, cutaneous swelling, leukocytosis, and intensification of any preexisting eosinophilia, edema, rashes, tachycardia, and headache. If microfilariae are present in the eye, further ocular damage may result. Other side effects are relatively mild and range from malaise, headache, and arthralgias to gastrointestinal symptoms.

Definition

ChEBI: Diethylcarbamazine is a N-methylpiperazine and a N-carbamoylpiperazine.

Manufacturing Process

To 50 cc of water was added 18 grams of 1-methylpiperazine dihydrochloride and 8.34 grams of sodium hydroxide. When solution had been effected the beaker was cooled to 10°C and with stirring, 4.17 grams of sodium hydroxide dissolved in 15 cc of water and 14 grams of diethyl carbamyl chloride were added simultaneously. When all had been added, the solution was extracted 3 times with ether which was then dried and filtered. The ether solution was saturated with dry hydrogen chloride. A yellow gum appeared which on trituration gave a white, hygroscopic solid which was filtered and dried in a drying pistol. The N,N-diethyl-4-methyl-1-piperazine-carboxamide hydrochloride had a melting point of 150°-155°C.
If the compound itself is desired, the salt is dissolved in water and the solution saturated with a mild alkali such as potassium carbonate. The product is then extracted with chloroform, dried, and after removal of the chloroform, distilled.

Therapeutic Function

Anthelmintic

Synthesis Reference(s)

The Journal of Organic Chemistry, 13, p. 144, 1948 DOI: 10.1021/jo01159a019
Diethylcarbamazine

Antimicrobial activity

Useful activity is restricted to filarial worms. It is adulticidal and microfilaricidal against Loa loa. Against Wuchereria bancrofti and Brugia malayi it is predominantly microfilaricidal, but slowly kills adult worms. It kills microfilariae, but not adults, of Onchocerca volvulus.

Pharmaceutical Applications

A carbamyl derivative of piperazine formulated as the citrate. It is readily soluble in water and slightly hygroscopic.

Mechanism of action

Although studied extensively, the mechanism of action of DEC remains unknown. Diethylcarbamazine appears to be the active form of the drug, with a very rapid onset of action (within minutes), but of interest is the fact that the drug is inactive in vitro, suggesting that activation of a cellular component is essential to the filaricidal action. Three mechanisms have been suggested. The first is involvement of blood platelets triggered by the action of filarial excretory antigens. A complex reaction is thought to occur between the drug, the antigen, and platelets. Although these authors were unable to show a direct action of the drug on the microfalaria, a more recent study showed that DEC produced morphological damage to the microfalaria. The damage consisted of the loss of the cellular sheath, exposing antigenic determinants to immune defense mechanisms. Severe damage then occurred to microfalaria organelles, leading to death. The second is inhibition of microtubule polymerization and disruption of preformed microtubules. The third is interference with arachidonic acid metabolism. Diethylcarbamazine is known to have anti-inflammatory action, which appears to involve blockage at cyclooxygenase and leukotriene A4 synthase (leukotriene synthesis). This action appears to alter vascular and cellular adhesiveness and cell activation. This latter action would suggest a possible relationship between the first and third mechanism.

Pharmacokinetics

Oral absorption: >90%
C_max 200 mg: 1.5–2 mg/L after 2 h
Plasma half-life: c. 6–12 h
Volume of distribution: 107–371 L
Plasma protein binding: Very low
Like piperazine (to which it is related), diethylcarbamazine is rapidly and completely absorbed. About half the dose is excreted unchanged in the urine; the rest is metabolized and eliminated by renal and extrarenal routes.

Clinical Use

Filariasis
It has also been used for visceral larva migrans, but experience is limited and there is little evidence of its efficacy.

Side effects

In uninfected people, diethylcarbamazine has virtually no side effects, but in those with various forms of filariasis it has unpleasant effects primarily due to the death of bloodor skin-dwelling microfilariae. Severe reactions (‘Mazzotti reactions’), most frequently of the skin, occur in patients with onchocerciasis and may also be systemic with fever, headache, prostration, nausea, joint and muscle pain, vertigo, tachycardia, cough and respiratory distress, hypotension and ocular signs. In patients with L. loa who harbor very large numbers of microfilariae in their blood, neurological problems may be very severe. Cardiological damage has also been reported. In patients with W. bancrofti and B. malayi high fever occurs in the first few days after treatment. Reversible proteinuria may occur.

Safety Profile

Poison by intraperitoneal route. Human systemic effects by ingestion: allergc dermatitis. An experimental teratogen. Mutation data reported. When heated to decomposition it emits toxic fumes of NOx and HCl. An additive permitted in the food and drinking water of animals and/or for the treatment of food-producing animals.

Synthesis

Diethylcarbamazine, N, N-diethyl-4-methyl-1-piperazincarboxamide (38.1.13), is made by acylating 1-methylpiperazine with diethylcarbamoylchloride.

Metabolism

The metabolism of DEC leads to the compounds shown in Figure 39.18 plus trace amounts of methylpiperazine and piperazine. Nearly all of the metabolites appear in the urine. As much as 10 to 20% of the drug is excreted unchanged. As indicated by the rapid action of the drug, it would appear that none of the metabolites are involved in the therapeutic action of DEC.