c.
Cyanosis of extremities. respect to all other clinical manifestations, there is general
d. Constricted pupils. similarity between carbamates and organophosphates. 393
2. Internal— Carbamates are rapidly metabolised. They are rapidly
a. Congestion of GI tract; garlicky or kerosene-like odour hydrolysed by liver enzymes to methyl carbamic acid and a
of contents. variety of low toxicity phenolic substances. These metabolites
b. Pulmonary and cerebral oedema. may sometimes be measured in urine as long as 2 to 3 days
c. Generalised visceral congestion. after significant pesticide absorption.
Miosis, a muscarinic effect, is characteristic of severe and
Forensic Issues moderately severe poisonings, but may appear late. Pupil dila-
Discussed at the end of the chapter, together with all the other tion may occur as a nicotinic effect and may be present in up
pesticides. to 10% of patients.
Sinus tachycardia with ST segment depression may occur
Carbamates early in the course of poisoning. Repolarisation abnormalities
Carbamates are as popular as organophosphates in their role as may occur and are generally transient.
insecticides (and fungicides) and share a number of similari- Dyspnoea is a common manifestation of carbamate expo-
ties. Only the differentiating features will be discussed. Indian sure.
brands are listed in Table 28.3. Chest tightness, bronchospasm, increased pulmonary secre-
Chapter 28 Pesticides
tions, and rales may develop secondary to muscarinic effects.
Usual Fatal Dose Acute lung injury (pulmonary oedema) is a potential clinical
Toxicity Rating*: manifestation of severe carbamate poisoning and is attributed
The following are extremely toxic (LD50: 1 to 50 mg/kg), to the muscarinic action of the insecticide. Contributing factors
or highly toxic (LD50: 51 to 500 mg/kg)— to the development of pulmonary oedema include bradycardia
Aminocarb, Bendiocarb, Benfuracarb, Carbaryl, and weakened cardiac contraction from an accumulation of
Carbofuran, Dimetan, Dimetilan, Dioxacarb, Formetanate, acetylcholine on the cardiovascular system. Hypoxia may
Methiocarb, Methomyl, Oxamyl, Propoxur. develop due to increasing capillary permeability.
The following are moderately toxic (LD50: 501 to 5000 Headache, dizziness, blurred vision, tremor, paresis,
mg/kg), or slightly toxic (LD50: more than 5000 mg/kg)— mental depression, coma, delayed neuropathies, various
Aldicarb, Bufencarb, Isoprocarb, MPMC, MTMC, dystonias, weakness, muscle twitching, and convulsions have
Pirimicarb. all been reported with carbamate poisoning. Children may
be more likely to develop CNS depression, convulsions, and
Mode of Action and Clinical Features hypotonia than the typical cholinergic syndrome. Absence of
Carbamates (like organophosphates) are inhibitors of acetyl- classic muscarinic effects has been reported in several children
cholinesterase, but carbamylate the serine moiety at the active intoxicated with carbamate insecticides. The presence of either
site instead of phosphorylation. This is a reversible type of a cardiac arrhythmia or respiratory failure is associated with a
binding and hence symptoms are less severe and of shorter higher incidence of fatal poisoning.
duration. As a result both morbidity and mortality are limited Various peripheral neuropathies have been reported after
when compared to organophosphate poisoning. Also, since carbamate use. The symptoms are similar to those seen with
carbamates do not penetrate the CNS to the same extent as organophosphates. Acute pancreatitis has been reported with
organophosphates, CNS toxicity is likewise much less. With propoxur.
Table 28.3: Common Carbamates
Generic Name Brand Name
Aldicarb Aldrin, Temik
Carbaryl Agrovin, Agroyl, Bangvin 50, Caravet, Corovin, Hexavin, Kevin 50, Kilex Carbaryl, Sevidal, Sevin 50,
Sujacarb, Sulfarl 50
Carbaryl + Gamma BHC Sevidol
Carbofuran Agrofuron 3G, Carbocil 3, Carburan, Crane, Furadan 3G, Hexafuran, VegFru Diafuran
Carbosulfan Marshal
Fenobucarb Merlino
Methomyl Astra, Dunet, Lannate, Lannet, Mathoyl
MPMC (Xylylcarb) Bipuin
MTMC (Metolcarb) Emisan
Propoxur Baygon, Isocarb, Protox Bait
Thiodicarb Larvin
* Partly as per the Insecticide Rules, 1971.
Convulsions can be controlled with a benzodiazepine
394 Diagnosis
(diazepam or lorazepam). If they persist or recur, administer
In the case of carbamate poisoning, measurement of cholinest- phenobarbitone.
erase activity in blood may be misleading due to in vitro reac-
tivation of carbamylated enzyme. In vitro decarbamylation
Organochlorines
has been found to be promoted by dilution of the sample. The Organochlorine pesticides are one variety of chlorinated hydro-
carbamylated sample should be stored undiluted and refriger- carbons. There are 4 distinct categories of these pesticides:
ated or frozen. Carbamylated cholinesterase activity follows a 1. DDT and analogues—for example, DDT (dichlorodiphe-
non-linear kinetic pattern over time, whereas phosphorylated nyltrichloroethane), and methoxychlor.
enzyme activity is linear. At inhibition of greater than 40%, the 2. Benzene hexachloride group—for example, benzene hexachlo-
non-linear pattern characteristic of carbamates is easily mapped. ride (BHC), and gamma-hexachlorocyclohexane (lindane).
One technique for assessing absorption of the principal 3. Cyclodienes and related compounds—for example, aldrin,
N-methyl carbamate compounds is measurement of specific dieldrin, endosulfan (thiodan), endrin, isobenzan, chlordane,
phenolic metabolites in urine, e.g. carbaryl (alpha-naphthol), chlordecone (kepone), heptachlor, mirex (dechlorane).
Section 8 Hydrocarbons and Pesticides
carbofuran (carbofuranphenol) propoxur (isopropoxyphenol). 4. Toxaphene and related compounds—for example, toxaphene.
Chest X-ray should be obtained in all symptomatic patients. Table 28.4 lists Indian brand names of organochlorine
The major cause of morbidity and mortality in carbamate pesticides.
insecticide poisonings is respiratory failure and associated Physical Appearance
pulmonary oedema.
These compounds are available as dusting powders, wettable
Treatment powders, emulsions, granules and solutions.
An important differentiating point from organophosphates is
that oximes are generally not recommended, while atropine
Uses
can be given. Especially in carbaryl poisoning, oxime therapy ■■ Insecticide.
can lead to the production of a carbamylated oxime which may ■■ Gamma benzene hexachloride is used as a scabicide (treat-
be a more potent acetylcholinesterase inhibitor than carbaryl ment of scabies), and a pediculocide (eradication of head
itself. With other carbamate insecticides (particularly aldicarb), lice). It is available as topical ointment, cream, or lotion.
oximes may be a useful adjunct to atropine therapy. In 1986, a Some Indian brand names include Bexarid (Shalaks), Gab
consensus of international experts concluded that pralidoxime (Gufic), Gamaric (Euphonic), Scaboma (Glenmark), and
can be used in conjunction with atropine for specific indica- Ultrascab (Perch).
tions as follows:
■■ Life-threatening symptoms such as severe muscle weak- Usual Fatal Dose
ness, fasciculations, paralysis, or decreased respiratory ■■ DDT, lindane: 15 to 30 grams.
effort. ■■ Aldrin, dieldrin, endrin : 2 to 6 grams.
■■ Continued excessive requirements of atropine. Toxicity Rating: Dieldrin is placed in the “extremely toxic”
■■ Concomitant organophosphate and carbamate exposure. category (LD50: 1 to 50 mg/kg), while DDT, endosulfan, and
In all cases, administer atropine in repeated doses intrave- lindane are considered “highly toxic”(LD50: 51 to 500 mg/kg),
nously until atropinisation is achieved (indicated by drying of as per the Insecticide Rules, 1971.
pulmonary secretions). Adult dose—2 to 4 mg IV every 10 to In addition, the following are extremely toxic: endrin,
15 minutes. Paediatric dose—0.05 mg/kg IV every 10 to 15 aldrin, chlordane, and toxaphene, while these are highly toxic:
minutes. kepone, heptachlor, mirex. The following are least toxic:
Table 28.4: Common Organochlorine Pesticides
Generic Name Brand Name
Aldrin Agroaldrin, Alcrop, Alditon, Aldrex, Aldrin 30, Mildrin 30, Tarmahit 30
BHC Agrobenz D10, Agro BHC, Gamazene, Gammexane, Haxaman, Hexidole Hilbleach 50WP, Kargo BHC, Premodole
10EC, Sevidol (with carbaryl), Solchlor, Sudarshan, Sulbenz 50, Sunbrand
Chlordane Agrodane 20EC, Chlordane, Mitox 20EC, Sudarshan 5EC, Termex, VegFru Chlortox
DDT DDT Sudarshan 50, Didinex 25EC, Ramdit, Ranodit, Soltax, Suldit 50, Sunbrand, Tafarol, Tafidex
Dicofol Kelthane, Klin
Endosulfan Agrosulfan, Chemusulfan, Endohit, Endoseed, Endosol, Endosulfan, Endoxin, Endotaf, Endovip, Ethsulfan,
Hexasulfan, Hildane, Hildon, Kenrilfan, Kesulfan, Marvel, Speed, Thiodan, Thiodon, Unidhan
Heptachlor Agrochlor D5, Agrodono, Heptachlor, Heptaf 50, Heptar, Heptox, VegFru Heptex
Lindane Agrodane, Bexarid, Canodane, Emscab, Gab, Gamaric, Gamascab, Kenodan, Lindane 20, Lindex, Linsuline, Lintaf,
Rasayan Lindane, Scabex, Scaboma, Scarab, Starbrand Lindane, Ultrascab
